接口泛型的类型推断

Question

我有一个接口，它接受两个明确的泛型参数：

interface ConnectedComponent<TSelectors, TActions> {
  selectors: TSelectors;
  actions: TActions;
  (props: SelectorProps<TSelectors> & ActionProps<TActions>): any;
}

以下是我如何使用它的方法：

let selectors = { ... };
let actions = { ... };

let Counter: ConnectedComponent<typeof selectors, typeof actions> = props => { ... };
Counter.selectors = selectors;
Counter.actions = actions;

我更希望从指定的属性中推断出通用类型：

let Counter: ConnectedComponent = { ... };
Counter.selectors = { ... };
Counter.actions = { ... };

然而，我不知道如何在接口中捕获typeof Counter.selectors和typeof Counter.actions。

- Dan Prince

Answer 1

唯一的方法是使用额外的函数并利用函数推理行为。要获得对函数参数的推理，我们需要使用返回函数的函数方法：

interface ConnectedComponent<TSelectors, TActions> {
    selectors: TSelectors;
    actions: TActions;
    (props: SelectorProps<TSelectors> & ActionProps<TActions>): any;
}

function createConnectedComponent<TSelectors, TActions>(props: { selectors: TSelectors; actions: TActions; }): (fn: (props: SelectorProps<TSelectors> & ActionProps<TActions>) => any) => ConnectedComponent<TSelectors, TActions> {
    return fn => Object.assign(fn, props);
}
let Counter2 = createConnectedComponent({
    selectors: {
        // ...
    },
    actions: {
        // ...
    }
})(p => { /*...*/ }); //p is TSelectors & TActions as expected

- Titian Cernicova-Dragomir