Mixing
how to get union types from array in flow?
I have array of text strings and I'm using it in another place. How to convert it in union types?
how to get:
type Message = 'hello world' | ...
from
const messages = ['hello world', ...]
flowtype
asked Dec 31 '18 at 12:54
Kherel KetchilKherel Ketchil
236
add a comment |
I have array of text strings and I'm using it in another place. How to convert it in union types?
how to get:
type Message = 'hello world' | ...
from
const messages = ['hello world', ...]
flowtype
asked Dec 31 '18 at 12:54
Kherel KetchilKherel Ketchil
236
add a comment |
I have array of text strings and I'm using it in another place. How to convert it in union types?
how to get:
type Message = 'hello world' | ...
from
const messages = ['hello world', ...]
flowtype
asked Dec 31 '18 at 12:54
Kherel KetchilKherel Ketchil
236
I have array of text strings and I'm using it in another place. How to convert it in union types?
how to get:
type Message = 'hello world' | ...
from
const messages = ['hello world', ...]
flowtype
flowtype
asked Dec 31 '18 at 12:54
Kherel KetchilKherel Ketchil
236
asked Dec 31 '18 at 12:54
Kherel KetchilKherel Ketchil
236
edited Jan 2 at 9:19
Kherel Ketchil
asked Dec 31 '18 at 12:54
Kherel KetchilKherel Ketchil
236
asked Dec 31 '18 at 12:54
Kherel KetchilKherel Ketchil
236
asked Dec 31 '18 at 12:54
Kherel KetchilKherel Ketchil
236
236
add a comment |
add a comment |
1 Answer
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This is tricky because Flow should infer a tuple type with literal string elements for the type of messages, but instead it infers the type as Array<string>. That means that the information containing the content of each string is lost. In theory you should be able to write type Message = $ElementType<typeof messages, number>, but that does not work as of Flow v0.89.0.
What you can do is express the messages in a form where Flow does preserve literal type information, such as keys in an object, and extract both the type and the list of messages from there:
const messageMap = {
"hello world": 1, // you can use whatever you want for the values
"goodbye": 2
}
const messages = Object.keys(messageMap)
type Message = $Keys<typeof messageMap>
answered Jan 2 at 20:43
Jesse HallettJesse Hallett
1,2881321
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
This is tricky because Flow should infer a tuple type with literal string elements for the type of messages, but instead it infers the type as Array<string>. That means that the information containing the content of each string is lost. In theory you should be able to write type Message = $ElementType<typeof messages, number>, but that does not work as of Flow v0.89.0.
What you can do is express the messages in a form where Flow does preserve literal type information, such as keys in an object, and extract both the type and the list of messages from there:
const messageMap = {
"hello world": 1, // you can use whatever you want for the values
"goodbye": 2
}
const messages = Object.keys(messageMap)
type Message = $Keys<typeof messageMap>
answered Jan 2 at 20:43
Jesse HallettJesse Hallett
1,2881321
add a comment |
This is tricky because Flow should infer a tuple type with literal string elements for the type of messages, but instead it infers the type as Array<string>. That means that the information containing the content of each string is lost. In theory you should be able to write type Message = $ElementType<typeof messages, number>, but that does not work as of Flow v0.89.0.
What you can do is express the messages in a form where Flow does preserve literal type information, such as keys in an object, and extract both the type and the list of messages from there:
const messageMap = {
"hello world": 1, // you can use whatever you want for the values
"goodbye": 2
}
const messages = Object.keys(messageMap)
type Message = $Keys<typeof messageMap>
answered Jan 2 at 20:43
Jesse HallettJesse Hallett
1,2881321
add a comment |
This is tricky because Flow should infer a tuple type with literal string elements for the type of messages, but instead it infers the type as Array<string>. That means that the information containing the content of each string is lost. In theory you should be able to write type Message = $ElementType<typeof messages, number>, but that does not work as of Flow v0.89.0.
What you can do is express the messages in a form where Flow does preserve literal type information, such as keys in an object, and extract both the type and the list of messages from there:
const messageMap = {
"hello world": 1, // you can use whatever you want for the values
"goodbye": 2
}
const messages = Object.keys(messageMap)
type Message = $Keys<typeof messageMap>
answered Jan 2 at 20:43
Jesse HallettJesse Hallett
1,2881321
This is tricky because Flow should infer a tuple type with literal string elements for the type of messages, but instead it infers the type as Array<string>. That means that the information containing the content of each string is lost. In theory you should be able to write type Message = $ElementType<typeof messages, number>, but that does not work as of Flow v0.89.0.
What you can do is express the messages in a form where Flow does preserve literal type information, such as keys in an object, and extract both the type and the list of messages from there:
const messageMap = {
"hello world": 1, // you can use whatever you want for the values
"goodbye": 2
}
const messages = Object.keys(messageMap)
type Message = $Keys<typeof messageMap>
answered Jan 2 at 20:43
Jesse HallettJesse Hallett
1,2881321
answered Jan 2 at 20:43
Jesse HallettJesse Hallett
1,2881321
answered Jan 2 at 20:43
Jesse HallettJesse Hallett
1,2881321
answered Jan 2 at 20:43
Jesse HallettJesse Hallett
1,2881321
1,2881321
add a comment |
add a comment |
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