Mixing
swift : shortcut for guard “let self = …” ?
I'm working with data from JSON, I have to parse them into a swift object. I use this code :
struct MyGPSCoords {
var latitude:Double
var longitude:Double
var accuracy:Int
var datetime:NSDate
init?(infobrutFromJson_:[String:String]?)
{
guard let infobrut = infobrutFromJson_ else {
// first time the user sign up to the app, php server returns "null" in Json
return nil
}
guard
let lat:Double = Double(infobrut["latitude"] ?? "nil"),
let lng = Double(infobrut["longitude"] ?? "nil"),
let acc = Int(infobrut["accuracy"] ?? "nil"),
let dtm = NSDate(timeIntervalSince1970: Double(infobrut["time"] ?? "nil"))
else {
print("warning : unable to parse data from server. Returning nil");
return nil ; // position not NIL but format not expected => = nil
}
self.latitude = lat
self.longitude = lng
self.accuracy = acc
self.datetime = dtm
}
}
I want to make the "guard" statement as short as possible. For exemple, i added ?? "nil" so if one of the keys doesnt exist, Double("nil") = nil and the guard statement can handle. For NSDate, i made a extension with a convenience init? that return nil if its param is nil, so I can so the same.
Now my question is, can i do it even shorter by assigning directly to self.latitude the values right in the guard statement ? When I try this :
guard self.latitude = Double(infobrut["latitude"] ?? "nil"), ...
It says that it cannot cast from Double? to Double.. So, is there any way to make this guard even shorter and avoiding me to assign lat, lng, acc and dtm buffering variables ?
ios swift optional
asked Nov 19 '18 at 19:40
Jerem LachkarJerem Lachkar
236
|
show 2 more comments
I'm working with data from JSON, I have to parse them into a swift object. I use this code :
struct MyGPSCoords {
var latitude:Double
var longitude:Double
var accuracy:Int
var datetime:NSDate
init?(infobrutFromJson_:[String:String]?)
{
guard let infobrut = infobrutFromJson_ else {
// first time the user sign up to the app, php server returns "null" in Json
return nil
}
guard
let lat:Double = Double(infobrut["latitude"] ?? "nil"),
let lng = Double(infobrut["longitude"] ?? "nil"),
let acc = Int(infobrut["accuracy"] ?? "nil"),
let dtm = NSDate(timeIntervalSince1970: Double(infobrut["time"] ?? "nil"))
else {
print("warning : unable to parse data from server. Returning nil");
return nil ; // position not NIL but format not expected => = nil
}
self.latitude = lat
self.longitude = lng
self.accuracy = acc
self.datetime = dtm
}
}
I want to make the "guard" statement as short as possible. For exemple, i added ?? "nil" so if one of the keys doesnt exist, Double("nil") = nil and the guard statement can handle. For NSDate, i made a extension with a convenience init? that return nil if its param is nil, so I can so the same.
Now my question is, can i do it even shorter by assigning directly to self.latitude the values right in the guard statement ? When I try this :
guard self.latitude = Double(infobrut["latitude"] ?? "nil"), ...
It says that it cannot cast from Double? to Double.. So, is there any way to make this guard even shorter and avoiding me to assign lat, lng, acc and dtm buffering variables ?
ios swift optional
asked Nov 19 '18 at 19:40
Jerem LachkarJerem Lachkar
236
@Damon yes you can?var a: String = "1"; var b = Int(a); print(a, type(of: b));-->// 1 Optional<Int>
– Jordan
Nov 19 '18 at 19:49
Your properties should belet, notvar
– Paulw11
Nov 19 '18 at 19:54
3
You could useCodable?
– Paulw11
Nov 19 '18 at 20:00
DecodeMyGPSCoordsdirectly from JSON usingDecodable. Don't getinfobrutFromJson_throughNSJSONSerializerfirst
– Code Different
Nov 19 '18 at 20:03
1
Codable is great but if you JSON is using strings for number values, you'll have to declare them as strings in your model as well. If you have control over the API I would suggest fixing that first.
– EmilioPelaez
Nov 19 '18 at 20:23
|
show 2 more comments
I'm working with data from JSON, I have to parse them into a swift object. I use this code :
struct MyGPSCoords {
var latitude:Double
var longitude:Double
var accuracy:Int
var datetime:NSDate
init?(infobrutFromJson_:[String:String]?)
{
guard let infobrut = infobrutFromJson_ else {
// first time the user sign up to the app, php server returns "null" in Json
return nil
}
guard
let lat:Double = Double(infobrut["latitude"] ?? "nil"),
let lng = Double(infobrut["longitude"] ?? "nil"),
let acc = Int(infobrut["accuracy"] ?? "nil"),
let dtm = NSDate(timeIntervalSince1970: Double(infobrut["time"] ?? "nil"))
else {
print("warning : unable to parse data from server. Returning nil");
return nil ; // position not NIL but format not expected => = nil
}
self.latitude = lat
self.longitude = lng
self.accuracy = acc
self.datetime = dtm
}
}
I want to make the "guard" statement as short as possible. For exemple, i added ?? "nil" so if one of the keys doesnt exist, Double("nil") = nil and the guard statement can handle. For NSDate, i made a extension with a convenience init? that return nil if its param is nil, so I can so the same.
Now my question is, can i do it even shorter by assigning directly to self.latitude the values right in the guard statement ? When I try this :
guard self.latitude = Double(infobrut["latitude"] ?? "nil"), ...
It says that it cannot cast from Double? to Double.. So, is there any way to make this guard even shorter and avoiding me to assign lat, lng, acc and dtm buffering variables ?
ios swift optional
asked Nov 19 '18 at 19:40
Jerem LachkarJerem Lachkar
236
I'm working with data from JSON, I have to parse them into a swift object. I use this code :
struct MyGPSCoords {
var latitude:Double
var longitude:Double
var accuracy:Int
var datetime:NSDate
init?(infobrutFromJson_:[String:String]?)
{
guard let infobrut = infobrutFromJson_ else {
// first time the user sign up to the app, php server returns "null" in Json
return nil
}
guard
let lat:Double = Double(infobrut["latitude"] ?? "nil"),
let lng = Double(infobrut["longitude"] ?? "nil"),
let acc = Int(infobrut["accuracy"] ?? "nil"),
let dtm = NSDate(timeIntervalSince1970: Double(infobrut["time"] ?? "nil"))
else {
print("warning : unable to parse data from server. Returning nil");
return nil ; // position not NIL but format not expected => = nil
}
self.latitude = lat
self.longitude = lng
self.accuracy = acc
self.datetime = dtm
}
}
I want to make the "guard" statement as short as possible. For exemple, i added ?? "nil" so if one of the keys doesnt exist, Double("nil") = nil and the guard statement can handle. For NSDate, i made a extension with a convenience init? that return nil if its param is nil, so I can so the same.
Now my question is, can i do it even shorter by assigning directly to self.latitude the values right in the guard statement ? When I try this :
guard self.latitude = Double(infobrut["latitude"] ?? "nil"), ...
It says that it cannot cast from Double? to Double.. So, is there any way to make this guard even shorter and avoiding me to assign lat, lng, acc and dtm buffering variables ?
ios swift optional
ios swift optional
asked Nov 19 '18 at 19:40
Jerem LachkarJerem Lachkar
236
asked Nov 19 '18 at 19:40
Jerem LachkarJerem Lachkar
236
asked Nov 19 '18 at 19:40
Jerem LachkarJerem Lachkar
236
asked Nov 19 '18 at 19:40
Jerem LachkarJerem Lachkar
236
asked Nov 19 '18 at 19:40
Jerem LachkarJerem Lachkar
236
236
@Damon yes you can?var a: String = "1"; var b = Int(a); print(a, type(of: b));-->// 1 Optional<Int>
– Jordan
Nov 19 '18 at 19:49
Your properties should belet, notvar
– Paulw11
Nov 19 '18 at 19:54
3
You could useCodable?
– Paulw11
Nov 19 '18 at 20:00
DecodeMyGPSCoordsdirectly from JSON usingDecodable. Don't getinfobrutFromJson_throughNSJSONSerializerfirst
– Code Different
Nov 19 '18 at 20:03
1
Codable is great but if you JSON is using strings for number values, you'll have to declare them as strings in your model as well. If you have control over the API I would suggest fixing that first.
– EmilioPelaez
Nov 19 '18 at 20:23
|
show 2 more comments
@Damon yes you can?var a: String = "1"; var b = Int(a); print(a, type(of: b));-->// 1 Optional<Int>
– Jordan
Nov 19 '18 at 19:49
Your properties should belet, notvar
– Paulw11
Nov 19 '18 at 19:54
3
You could useCodable?
– Paulw11
Nov 19 '18 at 20:00
DecodeMyGPSCoordsdirectly from JSON usingDecodable. Don't getinfobrutFromJson_throughNSJSONSerializerfirst
– Code Different
Nov 19 '18 at 20:03
1
Codable is great but if you JSON is using strings for number values, you'll have to declare them as strings in your model as well. If you have control over the API I would suggest fixing that first.
– EmilioPelaez
Nov 19 '18 at 20:23
@Damon yes you can?
var a: String = "1"; var b = Int(a); print(a, type(of: b)); --> // 1 Optional<Int>– Jordan
Nov 19 '18 at 19:49
@Damon yes you can?
var a: String = "1"; var b = Int(a); print(a, type(of: b)); --> // 1 Optional<Int>– Jordan
Nov 19 '18 at 19:49
Your properties should be
let, not var– Paulw11
Nov 19 '18 at 19:54
Your properties should be
let, not var– Paulw11
Nov 19 '18 at 19:54
3
3
You could use
Codable?– Paulw11
Nov 19 '18 at 20:00
You could use
Codable?– Paulw11
Nov 19 '18 at 20:00
Decode
MyGPSCoords directly from JSON using Decodable. Don't get infobrutFromJson_ through NSJSONSerializer first– Code Different
Nov 19 '18 at 20:03
Decode
MyGPSCoords directly from JSON using Decodable. Don't get infobrutFromJson_ through NSJSONSerializer first– Code Different
Nov 19 '18 at 20:03
1
1
Codable is great but if you JSON is using strings for number values, you'll have to declare them as strings in your model as well. If you have control over the API I would suggest fixing that first.
– EmilioPelaez
Nov 19 '18 at 20:23
Codable is great but if you JSON is using strings for number values, you'll have to declare them as strings in your model as well. If you have control over the API I would suggest fixing that first.
– EmilioPelaez
Nov 19 '18 at 20:23
|
show 2 more comments
3 Answers
3
active
oldest
votes
First, you should of course try to fix the JSON, since this JSON is malformed. Strings are not numbers in JSON. Assuming you cannot correct this broken JSON, the tool you want is flatMap, which converts T?? to T? (which is what guard-let expects).
guard
let lat = infobrut["latitude"].flatMap(Double.init),
let lng = infobrut["longitude"].flatMap(Double.init),
let acc = infobrut["accuracy"].flatMap(Int.init),
let dtm = infobrut["time"].flatMap(TimeInterval.init).flatMap(Date.init(timeIntervalSince1970:))
else {
print("warning : unable to parse data from server. Returning nil")
return nil // position not NIL but format not expected => = nil
}
I saw a lot of comments that Codable won't work here, but it absolutely will, and it's really what you should use. Here's one way (this is a little sloppy about its error messages, but it's simple):
struct MyGPSCoords: Decodable {
var latitude:Double
var longitude:Double
var accuracy:Int
var datetime:Date
enum CodingKeys: String, CodingKey {
case latitude, longitude, accuracy, datetime
}
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
guard
let lat = Double(try container.decode(String.self, forKey: .latitude)),
let lng = Double(try container.decode(String.self, forKey: .longitude)),
let acc = Int(try container.decode(String.self, forKey: .accuracy)),
let dtm = TimeInterval(try container.decode(String.self,
forKey: .datetime)).flatMap(Date.init(timeIntervalSince1970:))
else {
throw DecodingError.dataCorrupted(.init(codingPath: , debugDescription: "Could not decode"))
}
self.latitude = lat
self.longitude = lng
self.accuracy = acc
self.datetime = dtm
}
}
Or you can get really fancy with an internal helpful function and get rid of all the temporary variables and optionals through the power of throws.
struct MyGPSCoords: Decodable {
var latitude:Double
var longitude:Double
var accuracy:Int
var datetime:Date
enum CodingKeys: String, CodingKey {
case latitude, longitude, accuracy, datetime
}
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
func decodeBrokenJSON<T>(_ type: T.Type,
forKey key: CodingKeys) throws -> T
where T: Decodable & LosslessStringConvertible {
return try T.init(container.decode(String.self, forKey: key)) ?? {
throw DecodingError.dataCorruptedError(forKey: key,
in: container,
debugDescription: "Could not decode (key)")
}()
}
self.latitude = try decodeBrokenJSON(Double.self, forKey: .latitude)
self.longitude = try decodeBrokenJSON(Double.self, forKey: .longitude)
self.accuracy = try decodeBrokenJSON(Int.self, forKey: .accuracy)
self.datetime = Date(timeIntervalSince1970: try decodeBrokenJSON(TimeInterval.self, forKey: .datetime))
}
}
(IMO, this is a great example of how throws really shines and should be used much more than it commonly is.)
answered Nov 19 '18 at 20:11
Rob NapierRob Napier
200k28294420
Can drop the ; afterreturn niland your print
– CodeBender
Nov 19 '18 at 20:53
You don't need the explicitCodingKeysenum, since the keys are identical to the property names.
– NRitH
Nov 19 '18 at 21:44
@NRitH I don't think that's true. What do you pass askeyedBy:? Can you give it a try?
– Rob Napier
Nov 19 '18 at 21:49
I mean you don't need it if your struct implementsCodable. In my answer, I outline how this would work.
– NRitH
Nov 19 '18 at 21:59
add a comment |
The other solutions seem overly complicated. Simply make it
struct MyGPSCoords: Codable {
var latitude: Double?
var longitude: Double?
var accuracy: Int?
var datetime: Date?
var isValid {
return [latitude, longitude, accuracy, datetime].filter { $0 == nil }.isEmpty
}
}
// jsonData is whatever payload you get back from the URL request.
let coords = JSONDecoder().decode(jsonData, type: MyGPSCoords.self)
if !coords.isValid {
print("warning : unable to parse data from server.")
}
Since all of your properties are Optional, parsing can't fail if one or more of them is missing. The isValid check is much simpler than the guard let... clause in your original code.
EDIT: If, as Rob Napier suggests, all the JSON values are encoded as Strings, then here's another way to structure your MyGPSCoords:
struct MyGPSCoords: Codable {
// These are the Codable properties
fileprivate var latitudeString: String?
fileprivate var longitudeString: String?
fileprivate var accuracyString: String?
fileprivate var datetimeString: String?
// Default constant to use as a default check for validity
let invalid = Double.leastNonzeroMagnitude
// And these are the derived properties that you want users to use
var latitude: Double {
return Double(latitudeString ?? "(invalid)") ?? invalid
}
var longitude: Double {
return Double(longitudeString ?? "(invalid)") ?? invalid
}
var accuracy: Int {
return Int(accuracyString ?? "(invalid)") ?? Int(invalid)
}
var date: Date {
return <whatever-formatter-output-you-need>
}
var isValid {
return [latitudeString, longitudeString, accuracyString, datetimeString].filter { $0 == nil }.isEmpty
&& latitude != invalid && longitude != invalid
&& accuracy != Int(invalid) /* && however you compare dates */
}
}
answered Nov 19 '18 at 21:53
NRitHNRitH
7,57212432
This won't decode JSON strings into numeric values. The question strongly suggests the JSON is in the form{"latitude": "123.456"}, which is wrong, but a common way for JSON to be encoded. This also spreads Optionals to every user ofMyGPSCoords, which is a very bad design. The structure should be validated one time, and then there should be no optionals (as in the original code).
– Rob Napier
Nov 20 '18 at 1:06
i like the way you implement the isValid function.
– Shauket Sheikh
Nov 20 '18 at 2:22
add a comment |
What you want to do is not possible. The compiler already tells you so, even though the error message is a bit misleading. You can either use a guard let that creates a new variable, or you can use a guard with a boolean expression. In your case there is no let so the compiler tries to parse a boolean expression. Instead it sees the assignment and produces the error message that the types don’t match. If the types would match (as in guard self.latitude = 12.0) the error message would be clearer: error: use of '=' in a boolean context, did you mean '=='?
answered Nov 19 '18 at 20:19
SvenSven
20.3k44567
add a comment |
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3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
First, you should of course try to fix the JSON, since this JSON is malformed. Strings are not numbers in JSON. Assuming you cannot correct this broken JSON, the tool you want is flatMap, which converts T?? to T? (which is what guard-let expects).
guard
let lat = infobrut["latitude"].flatMap(Double.init),
let lng = infobrut["longitude"].flatMap(Double.init),
let acc = infobrut["accuracy"].flatMap(Int.init),
let dtm = infobrut["time"].flatMap(TimeInterval.init).flatMap(Date.init(timeIntervalSince1970:))
else {
print("warning : unable to parse data from server. Returning nil")
return nil // position not NIL but format not expected => = nil
}
I saw a lot of comments that Codable won't work here, but it absolutely will, and it's really what you should use. Here's one way (this is a little sloppy about its error messages, but it's simple):
struct MyGPSCoords: Decodable {
var latitude:Double
var longitude:Double
var accuracy:Int
var datetime:Date
enum CodingKeys: String, CodingKey {
case latitude, longitude, accuracy, datetime
}
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
guard
let lat = Double(try container.decode(String.self, forKey: .latitude)),
let lng = Double(try container.decode(String.self, forKey: .longitude)),
let acc = Int(try container.decode(String.self, forKey: .accuracy)),
let dtm = TimeInterval(try container.decode(String.self,
forKey: .datetime)).flatMap(Date.init(timeIntervalSince1970:))
else {
throw DecodingError.dataCorrupted(.init(codingPath: , debugDescription: "Could not decode"))
}
self.latitude = lat
self.longitude = lng
self.accuracy = acc
self.datetime = dtm
}
}
Or you can get really fancy with an internal helpful function and get rid of all the temporary variables and optionals through the power of throws.
struct MyGPSCoords: Decodable {
var latitude:Double
var longitude:Double
var accuracy:Int
var datetime:Date
enum CodingKeys: String, CodingKey {
case latitude, longitude, accuracy, datetime
}
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
func decodeBrokenJSON<T>(_ type: T.Type,
forKey key: CodingKeys) throws -> T
where T: Decodable & LosslessStringConvertible {
return try T.init(container.decode(String.self, forKey: key)) ?? {
throw DecodingError.dataCorruptedError(forKey: key,
in: container,
debugDescription: "Could not decode (key)")
}()
}
self.latitude = try decodeBrokenJSON(Double.self, forKey: .latitude)
self.longitude = try decodeBrokenJSON(Double.self, forKey: .longitude)
self.accuracy = try decodeBrokenJSON(Int.self, forKey: .accuracy)
self.datetime = Date(timeIntervalSince1970: try decodeBrokenJSON(TimeInterval.self, forKey: .datetime))
}
}
(IMO, this is a great example of how throws really shines and should be used much more than it commonly is.)
answered Nov 19 '18 at 20:11
Rob NapierRob Napier
200k28294420
Can drop the ; afterreturn niland your print
– CodeBender
Nov 19 '18 at 20:53
You don't need the explicitCodingKeysenum, since the keys are identical to the property names.
– NRitH
Nov 19 '18 at 21:44
@NRitH I don't think that's true. What do you pass askeyedBy:? Can you give it a try?
– Rob Napier
Nov 19 '18 at 21:49
I mean you don't need it if your struct implementsCodable. In my answer, I outline how this would work.
– NRitH
Nov 19 '18 at 21:59
add a comment |
First, you should of course try to fix the JSON, since this JSON is malformed. Strings are not numbers in JSON. Assuming you cannot correct this broken JSON, the tool you want is flatMap, which converts T?? to T? (which is what guard-let expects).
guard
let lat = infobrut["latitude"].flatMap(Double.init),
let lng = infobrut["longitude"].flatMap(Double.init),
let acc = infobrut["accuracy"].flatMap(Int.init),
let dtm = infobrut["time"].flatMap(TimeInterval.init).flatMap(Date.init(timeIntervalSince1970:))
else {
print("warning : unable to parse data from server. Returning nil")
return nil // position not NIL but format not expected => = nil
}
I saw a lot of comments that Codable won't work here, but it absolutely will, and it's really what you should use. Here's one way (this is a little sloppy about its error messages, but it's simple):
struct MyGPSCoords: Decodable {
var latitude:Double
var longitude:Double
var accuracy:Int
var datetime:Date
enum CodingKeys: String, CodingKey {
case latitude, longitude, accuracy, datetime
}
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
guard
let lat = Double(try container.decode(String.self, forKey: .latitude)),
let lng = Double(try container.decode(String.self, forKey: .longitude)),
let acc = Int(try container.decode(String.self, forKey: .accuracy)),
let dtm = TimeInterval(try container.decode(String.self,
forKey: .datetime)).flatMap(Date.init(timeIntervalSince1970:))
else {
throw DecodingError.dataCorrupted(.init(codingPath: , debugDescription: "Could not decode"))
}
self.latitude = lat
self.longitude = lng
self.accuracy = acc
self.datetime = dtm
}
}
Or you can get really fancy with an internal helpful function and get rid of all the temporary variables and optionals through the power of throws.
struct MyGPSCoords: Decodable {
var latitude:Double
var longitude:Double
var accuracy:Int
var datetime:Date
enum CodingKeys: String, CodingKey {
case latitude, longitude, accuracy, datetime
}
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
func decodeBrokenJSON<T>(_ type: T.Type,
forKey key: CodingKeys) throws -> T
where T: Decodable & LosslessStringConvertible {
return try T.init(container.decode(String.self, forKey: key)) ?? {
throw DecodingError.dataCorruptedError(forKey: key,
in: container,
debugDescription: "Could not decode (key)")
}()
}
self.latitude = try decodeBrokenJSON(Double.self, forKey: .latitude)
self.longitude = try decodeBrokenJSON(Double.self, forKey: .longitude)
self.accuracy = try decodeBrokenJSON(Int.self, forKey: .accuracy)
self.datetime = Date(timeIntervalSince1970: try decodeBrokenJSON(TimeInterval.self, forKey: .datetime))
}
}
(IMO, this is a great example of how throws really shines and should be used much more than it commonly is.)
answered Nov 19 '18 at 20:11
Rob NapierRob Napier
200k28294420
Can drop the ; afterreturn niland your print
– CodeBender
Nov 19 '18 at 20:53
You don't need the explicitCodingKeysenum, since the keys are identical to the property names.
– NRitH
Nov 19 '18 at 21:44
@NRitH I don't think that's true. What do you pass askeyedBy:? Can you give it a try?
– Rob Napier
Nov 19 '18 at 21:49
I mean you don't need it if your struct implementsCodable. In my answer, I outline how this would work.
– NRitH
Nov 19 '18 at 21:59
add a comment |
First, you should of course try to fix the JSON, since this JSON is malformed. Strings are not numbers in JSON. Assuming you cannot correct this broken JSON, the tool you want is flatMap, which converts T?? to T? (which is what guard-let expects).
guard
let lat = infobrut["latitude"].flatMap(Double.init),
let lng = infobrut["longitude"].flatMap(Double.init),
let acc = infobrut["accuracy"].flatMap(Int.init),
let dtm = infobrut["time"].flatMap(TimeInterval.init).flatMap(Date.init(timeIntervalSince1970:))
else {
print("warning : unable to parse data from server. Returning nil")
return nil // position not NIL but format not expected => = nil
}
I saw a lot of comments that Codable won't work here, but it absolutely will, and it's really what you should use. Here's one way (this is a little sloppy about its error messages, but it's simple):
struct MyGPSCoords: Decodable {
var latitude:Double
var longitude:Double
var accuracy:Int
var datetime:Date
enum CodingKeys: String, CodingKey {
case latitude, longitude, accuracy, datetime
}
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
guard
let lat = Double(try container.decode(String.self, forKey: .latitude)),
let lng = Double(try container.decode(String.self, forKey: .longitude)),
let acc = Int(try container.decode(String.self, forKey: .accuracy)),
let dtm = TimeInterval(try container.decode(String.self,
forKey: .datetime)).flatMap(Date.init(timeIntervalSince1970:))
else {
throw DecodingError.dataCorrupted(.init(codingPath: , debugDescription: "Could not decode"))
}
self.latitude = lat
self.longitude = lng
self.accuracy = acc
self.datetime = dtm
}
}
Or you can get really fancy with an internal helpful function and get rid of all the temporary variables and optionals through the power of throws.
struct MyGPSCoords: Decodable {
var latitude:Double
var longitude:Double
var accuracy:Int
var datetime:Date
enum CodingKeys: String, CodingKey {
case latitude, longitude, accuracy, datetime
}
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
func decodeBrokenJSON<T>(_ type: T.Type,
forKey key: CodingKeys) throws -> T
where T: Decodable & LosslessStringConvertible {
return try T.init(container.decode(String.self, forKey: key)) ?? {
throw DecodingError.dataCorruptedError(forKey: key,
in: container,
debugDescription: "Could not decode (key)")
}()
}
self.latitude = try decodeBrokenJSON(Double.self, forKey: .latitude)
self.longitude = try decodeBrokenJSON(Double.self, forKey: .longitude)
self.accuracy = try decodeBrokenJSON(Int.self, forKey: .accuracy)
self.datetime = Date(timeIntervalSince1970: try decodeBrokenJSON(TimeInterval.self, forKey: .datetime))
}
}
(IMO, this is a great example of how throws really shines and should be used much more than it commonly is.)
answered Nov 19 '18 at 20:11
Rob NapierRob Napier
200k28294420
First, you should of course try to fix the JSON, since this JSON is malformed. Strings are not numbers in JSON. Assuming you cannot correct this broken JSON, the tool you want is flatMap, which converts T?? to T? (which is what guard-let expects).
guard
let lat = infobrut["latitude"].flatMap(Double.init),
let lng = infobrut["longitude"].flatMap(Double.init),
let acc = infobrut["accuracy"].flatMap(Int.init),
let dtm = infobrut["time"].flatMap(TimeInterval.init).flatMap(Date.init(timeIntervalSince1970:))
else {
print("warning : unable to parse data from server. Returning nil")
return nil // position not NIL but format not expected => = nil
}
I saw a lot of comments that Codable won't work here, but it absolutely will, and it's really what you should use. Here's one way (this is a little sloppy about its error messages, but it's simple):
struct MyGPSCoords: Decodable {
var latitude:Double
var longitude:Double
var accuracy:Int
var datetime:Date
enum CodingKeys: String, CodingKey {
case latitude, longitude, accuracy, datetime
}
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
guard
let lat = Double(try container.decode(String.self, forKey: .latitude)),
let lng = Double(try container.decode(String.self, forKey: .longitude)),
let acc = Int(try container.decode(String.self, forKey: .accuracy)),
let dtm = TimeInterval(try container.decode(String.self,
forKey: .datetime)).flatMap(Date.init(timeIntervalSince1970:))
else {
throw DecodingError.dataCorrupted(.init(codingPath: , debugDescription: "Could not decode"))
}
self.latitude = lat
self.longitude = lng
self.accuracy = acc
self.datetime = dtm
}
}
Or you can get really fancy with an internal helpful function and get rid of all the temporary variables and optionals through the power of throws.
struct MyGPSCoords: Decodable {
var latitude:Double
var longitude:Double
var accuracy:Int
var datetime:Date
enum CodingKeys: String, CodingKey {
case latitude, longitude, accuracy, datetime
}
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
func decodeBrokenJSON<T>(_ type: T.Type,
forKey key: CodingKeys) throws -> T
where T: Decodable & LosslessStringConvertible {
return try T.init(container.decode(String.self, forKey: key)) ?? {
throw DecodingError.dataCorruptedError(forKey: key,
in: container,
debugDescription: "Could not decode (key)")
}()
}
self.latitude = try decodeBrokenJSON(Double.self, forKey: .latitude)
self.longitude = try decodeBrokenJSON(Double.self, forKey: .longitude)
self.accuracy = try decodeBrokenJSON(Int.self, forKey: .accuracy)
self.datetime = Date(timeIntervalSince1970: try decodeBrokenJSON(TimeInterval.self, forKey: .datetime))
}
}
(IMO, this is a great example of how throws really shines and should be used much more than it commonly is.)
answered Nov 19 '18 at 20:11
Rob NapierRob Napier
200k28294420
edited Nov 19 '18 at 21:13
answered Nov 19 '18 at 20:11
Rob NapierRob Napier
200k28294420
answered Nov 19 '18 at 20:11
Rob NapierRob Napier
200k28294420
answered Nov 19 '18 at 20:11
Rob NapierRob Napier
200k28294420
200k28294420
Can drop the ; afterreturn niland your print
– CodeBender
Nov 19 '18 at 20:53
You don't need the explicitCodingKeysenum, since the keys are identical to the property names.
– NRitH
Nov 19 '18 at 21:44
@NRitH I don't think that's true. What do you pass askeyedBy:? Can you give it a try?
– Rob Napier
Nov 19 '18 at 21:49
I mean you don't need it if your struct implementsCodable. In my answer, I outline how this would work.
– NRitH
Nov 19 '18 at 21:59
add a comment |
Can drop the ; afterreturn niland your print
– CodeBender
Nov 19 '18 at 20:53
You don't need the explicitCodingKeysenum, since the keys are identical to the property names.
– NRitH
Nov 19 '18 at 21:44
@NRitH I don't think that's true. What do you pass askeyedBy:? Can you give it a try?
– Rob Napier
Nov 19 '18 at 21:49
I mean you don't need it if your struct implementsCodable. In my answer, I outline how this would work.
– NRitH
Nov 19 '18 at 21:59
Can drop the ; after
return nil and your print– CodeBender
Nov 19 '18 at 20:53
Can drop the ; after
return nil and your print– CodeBender
Nov 19 '18 at 20:53
You don't need the explicit
CodingKeys enum, since the keys are identical to the property names.– NRitH
Nov 19 '18 at 21:44
You don't need the explicit
CodingKeys enum, since the keys are identical to the property names.– NRitH
Nov 19 '18 at 21:44
@NRitH I don't think that's true. What do you pass as
keyedBy:? Can you give it a try?– Rob Napier
Nov 19 '18 at 21:49
@NRitH I don't think that's true. What do you pass as
keyedBy:? Can you give it a try?– Rob Napier
Nov 19 '18 at 21:49
I mean you don't need it if your struct implements
Codable. In my answer, I outline how this would work.– NRitH
Nov 19 '18 at 21:59
I mean you don't need it if your struct implements
Codable. In my answer, I outline how this would work.– NRitH
Nov 19 '18 at 21:59
add a comment |
The other solutions seem overly complicated. Simply make it
struct MyGPSCoords: Codable {
var latitude: Double?
var longitude: Double?
var accuracy: Int?
var datetime: Date?
var isValid {
return [latitude, longitude, accuracy, datetime].filter { $0 == nil }.isEmpty
}
}
// jsonData is whatever payload you get back from the URL request.
let coords = JSONDecoder().decode(jsonData, type: MyGPSCoords.self)
if !coords.isValid {
print("warning : unable to parse data from server.")
}
Since all of your properties are Optional, parsing can't fail if one or more of them is missing. The isValid check is much simpler than the guard let... clause in your original code.
EDIT: If, as Rob Napier suggests, all the JSON values are encoded as Strings, then here's another way to structure your MyGPSCoords:
struct MyGPSCoords: Codable {
// These are the Codable properties
fileprivate var latitudeString: String?
fileprivate var longitudeString: String?
fileprivate var accuracyString: String?
fileprivate var datetimeString: String?
// Default constant to use as a default check for validity
let invalid = Double.leastNonzeroMagnitude
// And these are the derived properties that you want users to use
var latitude: Double {
return Double(latitudeString ?? "(invalid)") ?? invalid
}
var longitude: Double {
return Double(longitudeString ?? "(invalid)") ?? invalid
}
var accuracy: Int {
return Int(accuracyString ?? "(invalid)") ?? Int(invalid)
}
var date: Date {
return <whatever-formatter-output-you-need>
}
var isValid {
return [latitudeString, longitudeString, accuracyString, datetimeString].filter { $0 == nil }.isEmpty
&& latitude != invalid && longitude != invalid
&& accuracy != Int(invalid) /* && however you compare dates */
}
}
answered Nov 19 '18 at 21:53
NRitHNRitH
7,57212432
This won't decode JSON strings into numeric values. The question strongly suggests the JSON is in the form{"latitude": "123.456"}, which is wrong, but a common way for JSON to be encoded. This also spreads Optionals to every user ofMyGPSCoords, which is a very bad design. The structure should be validated one time, and then there should be no optionals (as in the original code).
– Rob Napier
Nov 20 '18 at 1:06
i like the way you implement the isValid function.
– Shauket Sheikh
Nov 20 '18 at 2:22
add a comment |
The other solutions seem overly complicated. Simply make it
struct MyGPSCoords: Codable {
var latitude: Double?
var longitude: Double?
var accuracy: Int?
var datetime: Date?
var isValid {
return [latitude, longitude, accuracy, datetime].filter { $0 == nil }.isEmpty
}
}
// jsonData is whatever payload you get back from the URL request.
let coords = JSONDecoder().decode(jsonData, type: MyGPSCoords.self)
if !coords.isValid {
print("warning : unable to parse data from server.")
}
Since all of your properties are Optional, parsing can't fail if one or more of them is missing. The isValid check is much simpler than the guard let... clause in your original code.
EDIT: If, as Rob Napier suggests, all the JSON values are encoded as Strings, then here's another way to structure your MyGPSCoords:
struct MyGPSCoords: Codable {
// These are the Codable properties
fileprivate var latitudeString: String?
fileprivate var longitudeString: String?
fileprivate var accuracyString: String?
fileprivate var datetimeString: String?
// Default constant to use as a default check for validity
let invalid = Double.leastNonzeroMagnitude
// And these are the derived properties that you want users to use
var latitude: Double {
return Double(latitudeString ?? "(invalid)") ?? invalid
}
var longitude: Double {
return Double(longitudeString ?? "(invalid)") ?? invalid
}
var accuracy: Int {
return Int(accuracyString ?? "(invalid)") ?? Int(invalid)
}
var date: Date {
return <whatever-formatter-output-you-need>
}
var isValid {
return [latitudeString, longitudeString, accuracyString, datetimeString].filter { $0 == nil }.isEmpty
&& latitude != invalid && longitude != invalid
&& accuracy != Int(invalid) /* && however you compare dates */
}
}
answered Nov 19 '18 at 21:53
NRitHNRitH
7,57212432
This won't decode JSON strings into numeric values. The question strongly suggests the JSON is in the form{"latitude": "123.456"}, which is wrong, but a common way for JSON to be encoded. This also spreads Optionals to every user ofMyGPSCoords, which is a very bad design. The structure should be validated one time, and then there should be no optionals (as in the original code).
– Rob Napier
Nov 20 '18 at 1:06
i like the way you implement the isValid function.
– Shauket Sheikh
Nov 20 '18 at 2:22
add a comment |
The other solutions seem overly complicated. Simply make it
struct MyGPSCoords: Codable {
var latitude: Double?
var longitude: Double?
var accuracy: Int?
var datetime: Date?
var isValid {
return [latitude, longitude, accuracy, datetime].filter { $0 == nil }.isEmpty
}
}
// jsonData is whatever payload you get back from the URL request.
let coords = JSONDecoder().decode(jsonData, type: MyGPSCoords.self)
if !coords.isValid {
print("warning : unable to parse data from server.")
}
Since all of your properties are Optional, parsing can't fail if one or more of them is missing. The isValid check is much simpler than the guard let... clause in your original code.
EDIT: If, as Rob Napier suggests, all the JSON values are encoded as Strings, then here's another way to structure your MyGPSCoords:
struct MyGPSCoords: Codable {
// These are the Codable properties
fileprivate var latitudeString: String?
fileprivate var longitudeString: String?
fileprivate var accuracyString: String?
fileprivate var datetimeString: String?
// Default constant to use as a default check for validity
let invalid = Double.leastNonzeroMagnitude
// And these are the derived properties that you want users to use
var latitude: Double {
return Double(latitudeString ?? "(invalid)") ?? invalid
}
var longitude: Double {
return Double(longitudeString ?? "(invalid)") ?? invalid
}
var accuracy: Int {
return Int(accuracyString ?? "(invalid)") ?? Int(invalid)
}
var date: Date {
return <whatever-formatter-output-you-need>
}
var isValid {
return [latitudeString, longitudeString, accuracyString, datetimeString].filter { $0 == nil }.isEmpty
&& latitude != invalid && longitude != invalid
&& accuracy != Int(invalid) /* && however you compare dates */
}
}
answered Nov 19 '18 at 21:53
NRitHNRitH
7,57212432
The other solutions seem overly complicated. Simply make it
struct MyGPSCoords: Codable {
var latitude: Double?
var longitude: Double?
var accuracy: Int?
var datetime: Date?
var isValid {
return [latitude, longitude, accuracy, datetime].filter { $0 == nil }.isEmpty
}
}
// jsonData is whatever payload you get back from the URL request.
let coords = JSONDecoder().decode(jsonData, type: MyGPSCoords.self)
if !coords.isValid {
print("warning : unable to parse data from server.")
}
Since all of your properties are Optional, parsing can't fail if one or more of them is missing. The isValid check is much simpler than the guard let... clause in your original code.
EDIT: If, as Rob Napier suggests, all the JSON values are encoded as Strings, then here's another way to structure your MyGPSCoords:
struct MyGPSCoords: Codable {
// These are the Codable properties
fileprivate var latitudeString: String?
fileprivate var longitudeString: String?
fileprivate var accuracyString: String?
fileprivate var datetimeString: String?
// Default constant to use as a default check for validity
let invalid = Double.leastNonzeroMagnitude
// And these are the derived properties that you want users to use
var latitude: Double {
return Double(latitudeString ?? "(invalid)") ?? invalid
}
var longitude: Double {
return Double(longitudeString ?? "(invalid)") ?? invalid
}
var accuracy: Int {
return Int(accuracyString ?? "(invalid)") ?? Int(invalid)
}
var date: Date {
return <whatever-formatter-output-you-need>
}
var isValid {
return [latitudeString, longitudeString, accuracyString, datetimeString].filter { $0 == nil }.isEmpty
&& latitude != invalid && longitude != invalid
&& accuracy != Int(invalid) /* && however you compare dates */
}
}
answered Nov 19 '18 at 21:53
NRitHNRitH
7,57212432
edited Nov 20 '18 at 2:52
answered Nov 19 '18 at 21:53
NRitHNRitH
7,57212432
answered Nov 19 '18 at 21:53
NRitHNRitH
7,57212432
answered Nov 19 '18 at 21:53
NRitHNRitH
7,57212432
7,57212432
This won't decode JSON strings into numeric values. The question strongly suggests the JSON is in the form{"latitude": "123.456"}, which is wrong, but a common way for JSON to be encoded. This also spreads Optionals to every user ofMyGPSCoords, which is a very bad design. The structure should be validated one time, and then there should be no optionals (as in the original code).
– Rob Napier
Nov 20 '18 at 1:06
i like the way you implement the isValid function.
– Shauket Sheikh
Nov 20 '18 at 2:22
add a comment |
This won't decode JSON strings into numeric values. The question strongly suggests the JSON is in the form{"latitude": "123.456"}, which is wrong, but a common way for JSON to be encoded. This also spreads Optionals to every user ofMyGPSCoords, which is a very bad design. The structure should be validated one time, and then there should be no optionals (as in the original code).
– Rob Napier
Nov 20 '18 at 1:06
i like the way you implement the isValid function.
– Shauket Sheikh
Nov 20 '18 at 2:22
This won't decode JSON strings into numeric values. The question strongly suggests the JSON is in the form
{"latitude": "123.456"}, which is wrong, but a common way for JSON to be encoded. This also spreads Optionals to every user of MyGPSCoords, which is a very bad design. The structure should be validated one time, and then there should be no optionals (as in the original code).– Rob Napier
Nov 20 '18 at 1:06
This won't decode JSON strings into numeric values. The question strongly suggests the JSON is in the form
{"latitude": "123.456"}, which is wrong, but a common way for JSON to be encoded. This also spreads Optionals to every user of MyGPSCoords, which is a very bad design. The structure should be validated one time, and then there should be no optionals (as in the original code).– Rob Napier
Nov 20 '18 at 1:06
i like the way you implement the isValid function.
– Shauket Sheikh
Nov 20 '18 at 2:22
i like the way you implement the isValid function.
– Shauket Sheikh
Nov 20 '18 at 2:22
add a comment |
What you want to do is not possible. The compiler already tells you so, even though the error message is a bit misleading. You can either use a guard let that creates a new variable, or you can use a guard with a boolean expression. In your case there is no let so the compiler tries to parse a boolean expression. Instead it sees the assignment and produces the error message that the types don’t match. If the types would match (as in guard self.latitude = 12.0) the error message would be clearer: error: use of '=' in a boolean context, did you mean '=='?
answered Nov 19 '18 at 20:19
SvenSven
20.3k44567
add a comment |
What you want to do is not possible. The compiler already tells you so, even though the error message is a bit misleading. You can either use a guard let that creates a new variable, or you can use a guard with a boolean expression. In your case there is no let so the compiler tries to parse a boolean expression. Instead it sees the assignment and produces the error message that the types don’t match. If the types would match (as in guard self.latitude = 12.0) the error message would be clearer: error: use of '=' in a boolean context, did you mean '=='?
answered Nov 19 '18 at 20:19
SvenSven
20.3k44567
add a comment |
What you want to do is not possible. The compiler already tells you so, even though the error message is a bit misleading. You can either use a guard let that creates a new variable, or you can use a guard with a boolean expression. In your case there is no let so the compiler tries to parse a boolean expression. Instead it sees the assignment and produces the error message that the types don’t match. If the types would match (as in guard self.latitude = 12.0) the error message would be clearer: error: use of '=' in a boolean context, did you mean '=='?
answered Nov 19 '18 at 20:19
SvenSven
20.3k44567
What you want to do is not possible. The compiler already tells you so, even though the error message is a bit misleading. You can either use a guard let that creates a new variable, or you can use a guard with a boolean expression. In your case there is no let so the compiler tries to parse a boolean expression. Instead it sees the assignment and produces the error message that the types don’t match. If the types would match (as in guard self.latitude = 12.0) the error message would be clearer: error: use of '=' in a boolean context, did you mean '=='?
answered Nov 19 '18 at 20:19
SvenSven
20.3k44567
answered Nov 19 '18 at 20:19
SvenSven
20.3k44567
answered Nov 19 '18 at 20:19
SvenSven
20.3k44567
answered Nov 19 '18 at 20:19
SvenSven
20.3k44567
20.3k44567
add a comment |
add a comment |
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@Damon yes you can?
var a: String = "1"; var b = Int(a); print(a, type(of: b));-->// 1 Optional<Int>– Jordan
Nov 19 '18 at 19:49
Your properties should be
let, notvar– Paulw11
Nov 19 '18 at 19:54
3
You could use
Codable?– Paulw11
Nov 19 '18 at 20:00
Decode
MyGPSCoordsdirectly from JSON usingDecodable. Don't getinfobrutFromJson_throughNSJSONSerializerfirst– Code Different
Nov 19 '18 at 20:03
1
Codable is great but if you JSON is using strings for number values, you'll have to declare them as strings in your model as well. If you have control over the API I would suggest fixing that first.
– EmilioPelaez
Nov 19 '18 at 20:23