flow typing mismatch for function accepting a reducer
I want to create a function which does something to a reducer (it's not important what it is, just some transformation, similar to combineReducers). i have problem when i want to abstract the state for the reducer.
Here is the simplified reducer used for some component:
type someState = {
foo: number,
};
export const someSimpleReducer = (state: someState) => state;
type StateAbstract = {}; // this doesn't work
// type StateAbstract = any; // this works
and here the abstract transform function with abstracted state:
declare type SimpleReducer<S> = (state: S) => S;
export const transformReducer = (reducer: SimpleReducer<StateAbstract>) => ({
reducer,
});
transformReducer(someSimpleReducer);
i see the following flow error:
Flow: Cannot call
transformReducerwithsomeSimpleReducerbound toreducerbecause propertyfoois missing inStateAbstract[1] but exists insomeState[2] in the first argument
If i use type StateAbstract = any then i don't see any error...
How can i write StateAbstract type so it's not any, but is an object?
redux flowtype
asked Nov 25 '18 at 14:47
Jacek KolasaJacek Kolasa
531412
add a comment |
I want to create a function which does something to a reducer (it's not important what it is, just some transformation, similar to combineReducers). i have problem when i want to abstract the state for the reducer.
Here is the simplified reducer used for some component:
type someState = {
foo: number,
};
export const someSimpleReducer = (state: someState) => state;
type StateAbstract = {}; // this doesn't work
// type StateAbstract = any; // this works
and here the abstract transform function with abstracted state:
declare type SimpleReducer<S> = (state: S) => S;
export const transformReducer = (reducer: SimpleReducer<StateAbstract>) => ({
reducer,
});
transformReducer(someSimpleReducer);
i see the following flow error:
Flow: Cannot call
transformReducerwithsomeSimpleReducerbound toreducerbecause propertyfoois missing inStateAbstract[1] but exists insomeState[2] in the first argument
If i use type StateAbstract = any then i don't see any error...
How can i write StateAbstract type so it's not any, but is an object?
redux flowtype
asked Nov 25 '18 at 14:47
Jacek KolasaJacek Kolasa
531412
add a comment |
I want to create a function which does something to a reducer (it's not important what it is, just some transformation, similar to combineReducers). i have problem when i want to abstract the state for the reducer.
Here is the simplified reducer used for some component:
type someState = {
foo: number,
};
export const someSimpleReducer = (state: someState) => state;
type StateAbstract = {}; // this doesn't work
// type StateAbstract = any; // this works
and here the abstract transform function with abstracted state:
declare type SimpleReducer<S> = (state: S) => S;
export const transformReducer = (reducer: SimpleReducer<StateAbstract>) => ({
reducer,
});
transformReducer(someSimpleReducer);
i see the following flow error:
Flow: Cannot call
transformReducerwithsomeSimpleReducerbound toreducerbecause propertyfoois missing inStateAbstract[1] but exists insomeState[2] in the first argument
If i use type StateAbstract = any then i don't see any error...
How can i write StateAbstract type so it's not any, but is an object?
redux flowtype
asked Nov 25 '18 at 14:47
Jacek KolasaJacek Kolasa
531412
I want to create a function which does something to a reducer (it's not important what it is, just some transformation, similar to combineReducers). i have problem when i want to abstract the state for the reducer.
Here is the simplified reducer used for some component:
type someState = {
foo: number,
};
export const someSimpleReducer = (state: someState) => state;
type StateAbstract = {}; // this doesn't work
// type StateAbstract = any; // this works
and here the abstract transform function with abstracted state:
declare type SimpleReducer<S> = (state: S) => S;
export const transformReducer = (reducer: SimpleReducer<StateAbstract>) => ({
reducer,
});
transformReducer(someSimpleReducer);
i see the following flow error:
Flow: Cannot call
transformReducerwithsomeSimpleReducerbound toreducerbecause propertyfoois missing inStateAbstract[1] but exists insomeState[2] in the first argument
If i use type StateAbstract = any then i don't see any error...
How can i write StateAbstract type so it's not any, but is an object?
redux flowtype
redux flowtype
asked Nov 25 '18 at 14:47
Jacek KolasaJacek Kolasa
531412
asked Nov 25 '18 at 14:47
Jacek KolasaJacek Kolasa
531412
asked Nov 25 '18 at 14:47
Jacek KolasaJacek Kolasa
531412
asked Nov 25 '18 at 14:47
Jacek KolasaJacek Kolasa
531412
asked Nov 25 '18 at 14:47
Jacek KolasaJacek Kolasa
531412
531412
add a comment |
add a comment |
1 Answer
1
active
oldest
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declare type SimpleReducer<S> = (state: S) => S;
declares a type SimpleReducer which is a function that takes an S and returns an S.
transformReducer is a function that takes a SimpleReducer<StateAbstract> i.e. a function that takes a StateAbstract and returns a StateAbstract.
transformReducer shouldn't care about what type that reducer function takes and returns. Instead of using a concrete type use a generic:
export const transformReducer = <S>(reducer: SimpleReducer<S>) => ({reducer})
Here it is on Try Flow.
answered Nov 25 '18 at 15:24
StefanStefan
60028
Thanks! but what if i want to make suretransformReducerdoesn't accept any wrong functions? Reducer should acceptstateas anobject, notstring. So i want to throw error on this situation?const improperReducer = (state: string) => state;transformReducer(improperReducer);or maybe i am just overdiligent?
– Jacek Kolasa
Nov 25 '18 at 15:42
updated Try Flow
– Jacek Kolasa
Nov 25 '18 at 15:43
If you want to only allow reducers that take objects, thenSimpleReducershould be declared likeSimpleReducer = (state: Object) => Object. And transformReducer is simplytransformReducer = (reducer: SimpleReducer) => ({reducer}). Try Flow Example
– Stefan
Nov 25 '18 at 15:52
That makes perfect sense, thanks!
– Jacek Kolasa
Nov 25 '18 at 16:06
1
Oh and in case you want to keep SimpleReducer generic then you can specify the concrete type in transformReducer like so:transformReducer = (reducer: SimpleReducer<Object>) => ({ reducer })
– Stefan
Nov 25 '18 at 16:06
|
show 1 more comment
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1 Answer
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1 Answer
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oldest
votes
declare type SimpleReducer<S> = (state: S) => S;
declares a type SimpleReducer which is a function that takes an S and returns an S.
transformReducer is a function that takes a SimpleReducer<StateAbstract> i.e. a function that takes a StateAbstract and returns a StateAbstract.
transformReducer shouldn't care about what type that reducer function takes and returns. Instead of using a concrete type use a generic:
export const transformReducer = <S>(reducer: SimpleReducer<S>) => ({reducer})
Here it is on Try Flow.
answered Nov 25 '18 at 15:24
StefanStefan
60028
Thanks! but what if i want to make suretransformReducerdoesn't accept any wrong functions? Reducer should acceptstateas anobject, notstring. So i want to throw error on this situation?const improperReducer = (state: string) => state;transformReducer(improperReducer);or maybe i am just overdiligent?
– Jacek Kolasa
Nov 25 '18 at 15:42
updated Try Flow
– Jacek Kolasa
Nov 25 '18 at 15:43
If you want to only allow reducers that take objects, thenSimpleReducershould be declared likeSimpleReducer = (state: Object) => Object. And transformReducer is simplytransformReducer = (reducer: SimpleReducer) => ({reducer}). Try Flow Example
– Stefan
Nov 25 '18 at 15:52
That makes perfect sense, thanks!
– Jacek Kolasa
Nov 25 '18 at 16:06
1
Oh and in case you want to keep SimpleReducer generic then you can specify the concrete type in transformReducer like so:transformReducer = (reducer: SimpleReducer<Object>) => ({ reducer })
– Stefan
Nov 25 '18 at 16:06
|
show 1 more comment
declare type SimpleReducer<S> = (state: S) => S;
declares a type SimpleReducer which is a function that takes an S and returns an S.
transformReducer is a function that takes a SimpleReducer<StateAbstract> i.e. a function that takes a StateAbstract and returns a StateAbstract.
transformReducer shouldn't care about what type that reducer function takes and returns. Instead of using a concrete type use a generic:
export const transformReducer = <S>(reducer: SimpleReducer<S>) => ({reducer})
Here it is on Try Flow.
answered Nov 25 '18 at 15:24
StefanStefan
60028
Thanks! but what if i want to make suretransformReducerdoesn't accept any wrong functions? Reducer should acceptstateas anobject, notstring. So i want to throw error on this situation?const improperReducer = (state: string) => state;transformReducer(improperReducer);or maybe i am just overdiligent?
– Jacek Kolasa
Nov 25 '18 at 15:42
updated Try Flow
– Jacek Kolasa
Nov 25 '18 at 15:43
If you want to only allow reducers that take objects, thenSimpleReducershould be declared likeSimpleReducer = (state: Object) => Object. And transformReducer is simplytransformReducer = (reducer: SimpleReducer) => ({reducer}). Try Flow Example
– Stefan
Nov 25 '18 at 15:52
That makes perfect sense, thanks!
– Jacek Kolasa
Nov 25 '18 at 16:06
1
Oh and in case you want to keep SimpleReducer generic then you can specify the concrete type in transformReducer like so:transformReducer = (reducer: SimpleReducer<Object>) => ({ reducer })
– Stefan
Nov 25 '18 at 16:06
|
show 1 more comment
declare type SimpleReducer<S> = (state: S) => S;
declares a type SimpleReducer which is a function that takes an S and returns an S.
transformReducer is a function that takes a SimpleReducer<StateAbstract> i.e. a function that takes a StateAbstract and returns a StateAbstract.
transformReducer shouldn't care about what type that reducer function takes and returns. Instead of using a concrete type use a generic:
export const transformReducer = <S>(reducer: SimpleReducer<S>) => ({reducer})
Here it is on Try Flow.
answered Nov 25 '18 at 15:24
StefanStefan
60028
declare type SimpleReducer<S> = (state: S) => S;
declares a type SimpleReducer which is a function that takes an S and returns an S.
transformReducer is a function that takes a SimpleReducer<StateAbstract> i.e. a function that takes a StateAbstract and returns a StateAbstract.
transformReducer shouldn't care about what type that reducer function takes and returns. Instead of using a concrete type use a generic:
export const transformReducer = <S>(reducer: SimpleReducer<S>) => ({reducer})
Here it is on Try Flow.
answered Nov 25 '18 at 15:24
StefanStefan
60028
answered Nov 25 '18 at 15:24
StefanStefan
60028
answered Nov 25 '18 at 15:24
StefanStefan
60028
answered Nov 25 '18 at 15:24
StefanStefan
60028
60028
Thanks! but what if i want to make suretransformReducerdoesn't accept any wrong functions? Reducer should acceptstateas anobject, notstring. So i want to throw error on this situation?const improperReducer = (state: string) => state;transformReducer(improperReducer);or maybe i am just overdiligent?
– Jacek Kolasa
Nov 25 '18 at 15:42
updated Try Flow
– Jacek Kolasa
Nov 25 '18 at 15:43
If you want to only allow reducers that take objects, thenSimpleReducershould be declared likeSimpleReducer = (state: Object) => Object. And transformReducer is simplytransformReducer = (reducer: SimpleReducer) => ({reducer}). Try Flow Example
– Stefan
Nov 25 '18 at 15:52
That makes perfect sense, thanks!
– Jacek Kolasa
Nov 25 '18 at 16:06
1
Oh and in case you want to keep SimpleReducer generic then you can specify the concrete type in transformReducer like so:transformReducer = (reducer: SimpleReducer<Object>) => ({ reducer })
– Stefan
Nov 25 '18 at 16:06
|
show 1 more comment
Thanks! but what if i want to make suretransformReducerdoesn't accept any wrong functions? Reducer should acceptstateas anobject, notstring. So i want to throw error on this situation?const improperReducer = (state: string) => state;transformReducer(improperReducer);or maybe i am just overdiligent?
– Jacek Kolasa
Nov 25 '18 at 15:42
updated Try Flow
– Jacek Kolasa
Nov 25 '18 at 15:43
If you want to only allow reducers that take objects, thenSimpleReducershould be declared likeSimpleReducer = (state: Object) => Object. And transformReducer is simplytransformReducer = (reducer: SimpleReducer) => ({reducer}). Try Flow Example
– Stefan
Nov 25 '18 at 15:52
That makes perfect sense, thanks!
– Jacek Kolasa
Nov 25 '18 at 16:06
1
Oh and in case you want to keep SimpleReducer generic then you can specify the concrete type in transformReducer like so:transformReducer = (reducer: SimpleReducer<Object>) => ({ reducer })
– Stefan
Nov 25 '18 at 16:06
Thanks! but what if i want to make sure
transformReducer doesn't accept any wrong functions? Reducer should accept state as an object, not string. So i want to throw error on this situation? const improperReducer = (state: string) => state; transformReducer(improperReducer); or maybe i am just overdiligent?– Jacek Kolasa
Nov 25 '18 at 15:42
Thanks! but what if i want to make sure
transformReducer doesn't accept any wrong functions? Reducer should accept state as an object, not string. So i want to throw error on this situation? const improperReducer = (state: string) => state; transformReducer(improperReducer); or maybe i am just overdiligent?– Jacek Kolasa
Nov 25 '18 at 15:42
updated Try Flow
– Jacek Kolasa
Nov 25 '18 at 15:43
updated Try Flow
– Jacek Kolasa
Nov 25 '18 at 15:43
If you want to only allow reducers that take objects, then
SimpleReducer should be declared like SimpleReducer = (state: Object) => Object. And transformReducer is simply transformReducer = (reducer: SimpleReducer) => ({reducer}). Try Flow Example– Stefan
Nov 25 '18 at 15:52
If you want to only allow reducers that take objects, then
SimpleReducer should be declared like SimpleReducer = (state: Object) => Object. And transformReducer is simply transformReducer = (reducer: SimpleReducer) => ({reducer}). Try Flow Example– Stefan
Nov 25 '18 at 15:52
That makes perfect sense, thanks!
– Jacek Kolasa
Nov 25 '18 at 16:06
That makes perfect sense, thanks!
– Jacek Kolasa
Nov 25 '18 at 16:06
1
1
Oh and in case you want to keep SimpleReducer generic then you can specify the concrete type in transformReducer like so:
transformReducer = (reducer: SimpleReducer<Object>) => ({ reducer })– Stefan
Nov 25 '18 at 16:06
Oh and in case you want to keep SimpleReducer generic then you can specify the concrete type in transformReducer like so:
transformReducer = (reducer: SimpleReducer<Object>) => ({ reducer })– Stefan
Nov 25 '18 at 16:06
|
show 1 more comment
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