Question

每当我将reducer传递给redux的createStore时，某个地方的编译器会尝试分配GenericAction :> MyAction，我猜，它应该执行相反的MyAction :> GenericAction。我有什么遗失的吗？

编辑：strictFunctionTypes : false禁用错误，因此与方差相关。

是否有解决方法而没有停用strictFunctionTypes？

我在下面做了一个简化的例子。

//test helpers
function _typ<T>(): T {
  return undefined as any
}
function _tryAssign<X extends Y, Y>(): any {}

//redux stub
type GenericAction = { type: string; [k: string]: any }
type Reducer<S> = (state: S, action: GenericAction) => S
type StoreCreator = <S>(reducer: Reducer<S>) => any

///my code
const createStore = _typ<StoreCreator>()
const initialState = { a: 1 }
type State = typeof initialState
type MyActions = {
  type: "A1"
  payload: {
    pl1: string
  }
}

const reducer = (state: State, actions: MyActions) => state
// Type 'Action' is not assignable to type 'MyActions'.
createStore(reducer)

// Type 'Action' is not assignable to type 'MyActions'.
_tryAssign<typeof reducer, Reducer<any>>()

//MyActions is assignable to Action
_tryAssign<MyActions, GenericAction>()
//Action is not assignable to MyActions
_tryAssign<GenericAction, MyActions>()

Answer 1

https://github.com/piotrwitek/react-redux-typescript-guide建议使用redux ^ 4.0，或者如果使用redux 3.x则启用strictFunctionTypes : false。

打字稿推理，方差和redux.createStore

1 个答案: