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battled and won typings

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Ken
2019-01-31 11:21:05 -08:00
parent 578ad8221d
commit fceb24f985
5 changed files with 55 additions and 31 deletions
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18
playground/src/reducers/createReducer.ts
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@@ -1,9 +1,9 @@
import { Reducer } from 'redux';
import { ActionTypes, TodoAction } from '../actions';
import { ActionTypes, TodoAction, TodoActionLookup } from '../actions';
import { Draft, produce } from 'immer';
export type ImmerReducer<T> = (state: Draft<T>, action: TodoAction) => T;
export type HandlerMap<T> = { [actionType in ActionTypes]?: ImmerReducer<T> };
export type ImmerReducer<T, A = any> = (state: Draft<T>, action: A) => T;
export type HandlerMap<T> = { [actionType in ActionTypes]?: ImmerReducer<T, TodoActionLookup[actionType]> };
function isHandlerFunction<T>(handlerOrMap: HandlerMap<T> | ImmerReducer<T>): handlerOrMap is ImmerReducer<T> {
if (typeof handlerOrMap === 'function') {
@@ -13,12 +13,16 @@ function isHandlerFunction<T>(handlerOrMap: HandlerMap<T> | ImmerReducer<T>): ha
return false;
}
export function createReducer<T>(initialState: T, handlerOrMap: HandlerMap<T> | ImmerReducer<T>): Reducer<T> {
return function reducer(state = initialState, action: TodoAction): T {
export function createReducer<T, AType extends ActionTypes | never = never>(
initialState: T,
handlerOrMap: HandlerMap<T> | ImmerReducer<T, TodoActionLookup[AType]>
): Reducer<T> {
return function reducer(state = initialState, action: TodoAction | TodoActionLookup[AType]): T {
if (isHandlerFunction(handlerOrMap)) {
return produce(state, draft => handlerOrMap(draft, action));
return produce(state, draft => handlerOrMap(draft, action as TodoActionLookup[AType]));
} else if (handlerOrMap.hasOwnProperty(action.type)) {
return produce(state, draft => handlerOrMap[action.type](draft, action));
const handler = handlerOrMap[action.type] as ImmerReducer<T>;
return produce(state, draft => handler(draft, action));
} else {
return state;
}