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observe, typescript: index & mapped types #818

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observe, typescript: index & mapped types #818

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4 changes: 2 additions & 2 deletions src/api/observe.ts
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
import {IObservableArray, IArrayChange, IArraySplice} from "../types/observablearray";
import {ObservableMap, IMapChange} from "../types/observablemap";
import {IObjectChange} from "../types/observableobject";
import {IObjectDidChange} from "../types/observableobject";
import {IComputedValue} from "../core/computedvalue";

import {IObservableValue, IValueDidChange} from "../types/observablevalue";
Expand All @@ -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.

export function observe(object: Object, property: string, listener: (change: IValueDidChange<any>) => void, fireImmediately?: boolean): Lambda;
export function observe(thing, propOrCb?, cbOrFire?, fireImmediately?): Lambda {
if (typeof cbOrFire === "function")
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9 changes: 8 additions & 1 deletion src/types/observableobject.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -15,7 +15,14 @@ export interface IObservableObject {
"observable-object": IObservableObject;
}

// In 3.0, change to IObjectDidChange
export interface IObjectDidChange<T, K extends keyof T> {
name: K;
object: T;
type: "update" | "add";
oldValue?: T[K];
newValue: T[K];
}

export interface IObjectChange {
name: string;
object: any;
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