Mixing
Custom swift class properties passed by reference?
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I have a custom class that I've written an equal/not equal function test for. I'm trying to test if an object I've modified is equal to the original object, but whenever I modify the second object, the original object seems to be modified as well. Here's some sample code (you can run this in a Playground):
// Custom class
class MyClass {
var foo: Bool = false
static func ==(a: MyClass, b: MyClass) -> Bool {
return (a.foo == b.foo)
}
static func !=(a: MyClass, b: MyClass) -> Bool {
return !(a==b)
}
required init() {
// do nothing
}
}
let originalObj: MyClass = MyClass()
var tempObj: MyClass = MyClass()
tempObj = originalObj
tempObj.foo = true
print(originalObj.foo) // Output: "true" (?!?!)
print(tempObj == originalObj) // Output: "true" (?!?!)
Why does changing the value of tempObj change the value of originalObj, and how can I prevent this behavior?
swift class properties pass-by-reference
asked Jan 3 at 3:11
MattMatt
71741943
add a comment |
I have a custom class that I've written an equal/not equal function test for. I'm trying to test if an object I've modified is equal to the original object, but whenever I modify the second object, the original object seems to be modified as well. Here's some sample code (you can run this in a Playground):
// Custom class
class MyClass {
var foo: Bool = false
static func ==(a: MyClass, b: MyClass) -> Bool {
return (a.foo == b.foo)
}
static func !=(a: MyClass, b: MyClass) -> Bool {
return !(a==b)
}
required init() {
// do nothing
}
}
let originalObj: MyClass = MyClass()
var tempObj: MyClass = MyClass()
tempObj = originalObj
tempObj.foo = true
print(originalObj.foo) // Output: "true" (?!?!)
print(tempObj == originalObj) // Output: "true" (?!?!)
Why does changing the value of tempObj change the value of originalObj, and how can I prevent this behavior?
swift class properties pass-by-reference
asked Jan 3 at 3:11
MattMatt
71741943
tempObj = originalObjmakes both reference variables point to the same object in memory. Don't do that if you don't want both to be the same.
– rmaddy
Jan 3 at 3:21
class are reference types. You can use value types like structs and enums. in which case, when you will write, tempObj = originalObj, it will actually copy the object and hence any future changes to originalObj will not modify tempObj.
– Deepika
Jan 3 at 3:26
add a comment |
I have a custom class that I've written an equal/not equal function test for. I'm trying to test if an object I've modified is equal to the original object, but whenever I modify the second object, the original object seems to be modified as well. Here's some sample code (you can run this in a Playground):
// Custom class
class MyClass {
var foo: Bool = false
static func ==(a: MyClass, b: MyClass) -> Bool {
return (a.foo == b.foo)
}
static func !=(a: MyClass, b: MyClass) -> Bool {
return !(a==b)
}
required init() {
// do nothing
}
}
let originalObj: MyClass = MyClass()
var tempObj: MyClass = MyClass()
tempObj = originalObj
tempObj.foo = true
print(originalObj.foo) // Output: "true" (?!?!)
print(tempObj == originalObj) // Output: "true" (?!?!)
Why does changing the value of tempObj change the value of originalObj, and how can I prevent this behavior?
swift class properties pass-by-reference
asked Jan 3 at 3:11
MattMatt
71741943
I have a custom class that I've written an equal/not equal function test for. I'm trying to test if an object I've modified is equal to the original object, but whenever I modify the second object, the original object seems to be modified as well. Here's some sample code (you can run this in a Playground):
// Custom class
class MyClass {
var foo: Bool = false
static func ==(a: MyClass, b: MyClass) -> Bool {
return (a.foo == b.foo)
}
static func !=(a: MyClass, b: MyClass) -> Bool {
return !(a==b)
}
required init() {
// do nothing
}
}
let originalObj: MyClass = MyClass()
var tempObj: MyClass = MyClass()
tempObj = originalObj
tempObj.foo = true
print(originalObj.foo) // Output: "true" (?!?!)
print(tempObj == originalObj) // Output: "true" (?!?!)
Why does changing the value of tempObj change the value of originalObj, and how can I prevent this behavior?
swift class properties pass-by-reference
swift class properties pass-by-reference
asked Jan 3 at 3:11
MattMatt
71741943
asked Jan 3 at 3:11
MattMatt
71741943
asked Jan 3 at 3:11
MattMatt
71741943
asked Jan 3 at 3:11
MattMatt
71741943
asked Jan 3 at 3:11
MattMatt
71741943
71741943
tempObj = originalObjmakes both reference variables point to the same object in memory. Don't do that if you don't want both to be the same.
– rmaddy
Jan 3 at 3:21
class are reference types. You can use value types like structs and enums. in which case, when you will write, tempObj = originalObj, it will actually copy the object and hence any future changes to originalObj will not modify tempObj.
– Deepika
Jan 3 at 3:26
add a comment |
tempObj = originalObjmakes both reference variables point to the same object in memory. Don't do that if you don't want both to be the same.
– rmaddy
Jan 3 at 3:21
class are reference types. You can use value types like structs and enums. in which case, when you will write, tempObj = originalObj, it will actually copy the object and hence any future changes to originalObj will not modify tempObj.
– Deepika
Jan 3 at 3:26
tempObj = originalObj makes both reference variables point to the same object in memory. Don't do that if you don't want both to be the same.– rmaddy
Jan 3 at 3:21
tempObj = originalObj makes both reference variables point to the same object in memory. Don't do that if you don't want both to be the same.– rmaddy
Jan 3 at 3:21
class are reference types. You can use value types like structs and enums. in which case, when you will write, tempObj = originalObj, it will actually copy the object and hence any future changes to originalObj will not modify tempObj.
– Deepika
Jan 3 at 3:26
class are reference types. You can use value types like structs and enums. in which case, when you will write, tempObj = originalObj, it will actually copy the object and hence any future changes to originalObj will not modify tempObj.
– Deepika
Jan 3 at 3:26
add a comment |
1 Answer
1
active
oldest
votes
Classes in swift are Reference Types whereas Structs are Value Types. There are two ways to achieve what you want. You can either use struct instead of class or write a copy method for this class and use that method. Something like this
class MyClass {
var foo: Bool = false
static func ==(a: MyClass, b: MyClass) -> Bool {
return (a.foo == b.foo)
}
static func !=(a: MyClass, b: MyClass) -> Bool {
return !(a==b)
}
required init() {
// do nothing
}
func copy() -> MyClass {
let temp = MyClass()
temp.foo = foo
return temp
}
}
let originalObj: MyClass = MyClass()
var tempObj: MyClass = originalObj.copy()
answered Jan 3 at 3:28
MalikMalik
2,36811026
add a comment |
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
Classes in swift are Reference Types whereas Structs are Value Types. There are two ways to achieve what you want. You can either use struct instead of class or write a copy method for this class and use that method. Something like this
class MyClass {
var foo: Bool = false
static func ==(a: MyClass, b: MyClass) -> Bool {
return (a.foo == b.foo)
}
static func !=(a: MyClass, b: MyClass) -> Bool {
return !(a==b)
}
required init() {
// do nothing
}
func copy() -> MyClass {
let temp = MyClass()
temp.foo = foo
return temp
}
}
let originalObj: MyClass = MyClass()
var tempObj: MyClass = originalObj.copy()
answered Jan 3 at 3:28
MalikMalik
2,36811026
add a comment |
Classes in swift are Reference Types whereas Structs are Value Types. There are two ways to achieve what you want. You can either use struct instead of class or write a copy method for this class and use that method. Something like this
class MyClass {
var foo: Bool = false
static func ==(a: MyClass, b: MyClass) -> Bool {
return (a.foo == b.foo)
}
static func !=(a: MyClass, b: MyClass) -> Bool {
return !(a==b)
}
required init() {
// do nothing
}
func copy() -> MyClass {
let temp = MyClass()
temp.foo = foo
return temp
}
}
let originalObj: MyClass = MyClass()
var tempObj: MyClass = originalObj.copy()
answered Jan 3 at 3:28
MalikMalik
2,36811026
add a comment |
Classes in swift are Reference Types whereas Structs are Value Types. There are two ways to achieve what you want. You can either use struct instead of class or write a copy method for this class and use that method. Something like this
class MyClass {
var foo: Bool = false
static func ==(a: MyClass, b: MyClass) -> Bool {
return (a.foo == b.foo)
}
static func !=(a: MyClass, b: MyClass) -> Bool {
return !(a==b)
}
required init() {
// do nothing
}
func copy() -> MyClass {
let temp = MyClass()
temp.foo = foo
return temp
}
}
let originalObj: MyClass = MyClass()
var tempObj: MyClass = originalObj.copy()
answered Jan 3 at 3:28
MalikMalik
2,36811026
Classes in swift are Reference Types whereas Structs are Value Types. There are two ways to achieve what you want. You can either use struct instead of class or write a copy method for this class and use that method. Something like this
class MyClass {
var foo: Bool = false
static func ==(a: MyClass, b: MyClass) -> Bool {
return (a.foo == b.foo)
}
static func !=(a: MyClass, b: MyClass) -> Bool {
return !(a==b)
}
required init() {
// do nothing
}
func copy() -> MyClass {
let temp = MyClass()
temp.foo = foo
return temp
}
}
let originalObj: MyClass = MyClass()
var tempObj: MyClass = originalObj.copy()
answered Jan 3 at 3:28
MalikMalik
2,36811026
edited Jan 3 at 4:13
answered Jan 3 at 3:28
MalikMalik
2,36811026
answered Jan 3 at 3:28
MalikMalik
2,36811026
answered Jan 3 at 3:28
MalikMalik
2,36811026
2,36811026
add a comment |
add a comment |
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tempObj = originalObjmakes both reference variables point to the same object in memory. Don't do that if you don't want both to be the same.– rmaddy
Jan 3 at 3:21
class are reference types. You can use value types like structs and enums. in which case, when you will write, tempObj = originalObj, it will actually copy the object and hence any future changes to originalObj will not modify tempObj.
– Deepika
Jan 3 at 3:26