@ngrx/store (an observable redux implementation for angular (2) ) utilizes a specific pattern to assign the correct type to a reducer.
Check out the actual code here.
export const ActionTypes = {
FOO: type('foo'),
BAR: type('bar')
};
export class FooAction implements Action {
type = ActionTypes.FOO;
constructor(public payload: string) { }
}
export class BarAction implements Action {
type = ActionTypes.BAR;
constructor(public payload: number) { }
}
export type Actions
= Foo
| Bar;
This also includes a sample reducer:
export class SomeReducerState {
foo: string;
bar: number;
}
const initialState = {
foo: undefined,
bar: 0
};
export function someReducer(
state: SomeReducerState = initialState,
action: some.Actions
): SomeReducerState {
switch (action.type) {
case some.ActionTypes.FOO:
return Object.assign({}, state, { foo: action.payload });
case some.ActionTypes.BAR:
return Object.assign({}, state, { bar: action.payload });
default:
return state;
}
}
In TypeScript 2.0.x, the switch/case structure was used to determine the proper type for action.payload. For example, inside case some.ActionTypes.FOO, action.payload was assigned as string, while in BAR it was number. However, with TypeScript 2.1.x, it appears to default to any. Is there a workaround to achieve the same outcomes in 2.1.x? Or is it potentially a bug?