observe, typescript: index & mapped types #818
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Enable index types and mapped types on `IObjectdidChange` for better typecheck and inference
Igorbek
reviewed
Jan 21, 2018
| @@ -11,7 +11,7 @@ export function observe<T>(value: IObservableValue<T> | IComputedValue<T>, liste | |||
| export function observe<T>(observableArray: IObservableArray<T>, listener: (change: IArrayChange<T> | IArraySplice<T>) => void, fireImmediately?: boolean): Lambda; | |||
| export function observe<T>(observableMap: ObservableMap<T>, listener: (change: IMapChange<T>) => void, fireImmediately?: boolean): Lambda; | |||
| export function observe<T>(observableMap: ObservableMap<T>, property: string, listener: (change: IValueDidChange<T>) => void, fireImmediately?: boolean): Lambda; | |||
| export function observe(object: Object, listener: (change: IObjectChange) => void, fireImmediately?: boolean): Lambda; | |||
| export function observe<T>(object: T, listener: (change: IObjectDidChange<T, keyof T>) => void, fireImmediately?: boolean): Lambda; | |||
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Setting type of keys to keyof T is not quite correct in TS, unless T would represent an exact type (not supported yet).
Consider your T is { a; b; }, and your runtime observable object is { a: 1, b: 2, c: 3 } which is totally ok as it is assignable to T.
Now your listener can at most only expects "a" | "b" which is not aligned with the runtime possibility to receive "c".
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Yes, sure. Same thing exists in Object.keys function definitions in lib.d.ts: this function returns string[], not a keyof passed object. I think this can stay as it is.
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Enable index types and mapped types on
IObjectdidChangefor better typecheck and inference