接口泛型的类型推断答案

【问题标题】：Type inference from interface generics接口泛型的类型推断
【发布时间】：2018-06-11 14:27:22
【问题描述】：

我有一个带有两个显式泛型参数的接口：

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

这是我的使用方法：

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

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

我更愿意做的是从分配的属性中推断出泛型：

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

但是我不知道如何在界面中捕获typeof Counter.selectors 和typeof Counter.actions。

【问题讨论】：

标签： typescript generics type-inference

【解决方案1】：

做到这一点的唯一方法是使用额外的函数并利用函数的推理行为。为了推断函数的参数，我们需要使用一个返回函数方法的函数：

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

【讨论】：