小编jf1*_*234的帖子

为什么我不能像这样简单地输入我的减速器，而不在我的 redux 状态类型中添加“| undefined”？

const reducer: Reducer<ReduxState> = function(state: ReduxState, action: any) ...

额外的上下文::::

这工作正常：

export const reducer: Reducer<ReduxState | undefined> = function (
    state: ReduxState | undefined, 
    action: any
) {
    return state
}
export default reducer

但是，从 fxn 中删除状态参数“未定义”时不会：

export const reducer: Reducer<ReduxState | undefined> = function (
    state: ReduxState, 
    action: any
) {
    return state
}
export default reducer

这给出了一个错误：

Type '(state: ReduxState, action: any) => ReduxState' is not assignable to type 'Reducer<ReduxState | undefined, AnyAction>'.
  Types …