Typescript希望未定义的作为参数传递

Typescript:2.4.1

我正在尝试创建一个助手函数来生成redux操作创建者

我得到的是：

interface IAction<T extends string, P = undefined> {
    type: T;
    payload: P;
}

function createAction<T extends string>(type: T): () => IAction<T, undefined>;
function createAction<T extends string = '', U = undefined, V = {}>(type: T, actionCreator: (payload: U) => V): (payload: U) => IAction<T, V>;
function createAction<T extends string>(type: T, actionCreator?: (payload?: any) => any) {
    return (payload: any) => ({
        payload,
        type,
    });
}

enum ActionType {
    INCREMENT = 'COUNTER/INCREMENT',
    DECREMENT = 'COUNTER/DECREMENT',
    ASYNC_INCREMENT = 'COUNTER/ASYNC_INCREMENT',
}

const increment = createAction(ActionType.INCREMENT, () => ({ amount: 1 }));
const incrementBy = createAction(ActionType.INCREMENT, (amount: number) => amount);

尝试以调用

incrementBy

的相同方式调用它，例如

increment（42）

，我得到以下错误：

[ts] Argument of type '42' is not assignable to parameter of type 'undefined';

这是有效的：

增量（未定义）

---

有办法解决这个问题吗？

您只需创建另一个重载，它将返回一个没有参数的函数，而不是将

未定义的
作为唯一参数的函数

function createAction<T extends string>(type: T): () => IAction<T, undefined>;
function createAction<T extends string, V>(type: T, actionCreator: () => V): () => IAction<T, V>;
function createAction<T extends string, U, V>(type: T, actionCreator: (payload: U) => V): (payload: U) => IAction<T, V>;
function createAction<T extends string, U, V>(type: T, actionCreator?: (payload: U) => V): (payload: U) => IAction<T, V> {
    return (payload: any) => ({
        payload,
        type,
    });
}

函数createAction（类型：T）：（）=>iaAction；
函数createAction（类型：T，actionCreator:（）=>V:（）=>IAction；
函数createAction（类型：T，actionCreator:（有效载荷：U）=>V:（有效载荷：U）=>IAction；
函数createAction（类型：T，actionCreator？：（有效载荷：U）=>V:（有效载荷：U）=>IAction{
返回（有效载荷：任意）=>({
有效载荷，
类型，
});
}

但是，您的实现似乎对传递的函数没有任何作用。您可能希望这样做：

function createAction<T extends string>(type: T): () => IAction<T, undefined>;
function createAction<T extends string, V>(type: T, actionCreator: () => V): () => IAction<T, V>;
function createAction<T extends string, U, V>(type: T, actionCreator: (payload: U) => V): (payload: U) => IAction<T, V>;
function createAction<T extends string, U, V>(type: T, actionCreator?: (payload: U) => V): (payload: U) => IAction<T, V> {
    if (actionCreator) {
        return (payload: U) => ({
            payload: actionCreator(payload),
            type,
        });
    } else {
        return () => ({
            payload: undefined,
            type
        });
    }
}

函数createAction（类型：T）：（）=>iaAction；
函数createAction（类型：T，actionCreator:（）=>V:（）=>IAction；
函数createAction（类型：T，actionCreator:（有效载荷：U）=>V:（有效载荷：U）=>IAction；
函数createAction（类型：T，actionCreator？：（有效载荷：U）=>V:（有效载荷：U）=>IAction{
如果（actionCreator）{
返回（有效载荷：U）=>({
有效载荷：actionCreator（有效载荷），
类型，
});
}否则{
return（）=>({
有效载荷：未定义，
类型
});
}
}

function createAction<T extends string>(type: T): () => IAction<T, undefined>;
function createAction<T extends string, V>(type: T, actionCreator: () => V): () => IAction<T, V>;
function createAction<T extends string, U, V>(type: T, actionCreator: (payload: U) => V): (payload: U) => IAction<T, V>;
function createAction<T extends string, U, V>(type: T, actionCreator?: (payload: U) => V): (payload: U) => IAction<T, V> {
    if (actionCreator) {
        return (payload: U) => ({
            payload: actionCreator(payload),
            type,
        });
    } else {
        return () => ({
            payload: undefined,
            type
        });
    }
}