我正在创建一堆内部具有一些常用功能的组件,其中一个是处理渲染的组件。简化,它看起来像这样:
const render = (
instance: React.Component<{}, {flag: boolean}>,
cb: () => React.ReactNode
) => instance.state.flag ? cb() : '';
class Test extends React.Component<{}, {flag: boolean}> {
state = {flag: true};
render() { return render(this, () => '') }
}
但是,TypeScript对此设置不满意并说:'render' implicitly has return type 'any' because it does not have a return type annotation and is referenced directly or indirectly in one of its return expressions.
就个人而言,我看不到这个参考。
作为一个可能的线索,如果我这样重写这段代码:
const render = (
state: {flag: boolean},
cb: () => React.ReactNode
) => state.flag ? cb() : '';
class Test extends React.Component<{}, {flag: boolean}> {
state = {flag: true};
render() { return render(this.state, () => '') }
}
...一切运作良好,但我真的想要使用组件本身,因为现在看不到一些复杂性。
有什么问题?我能用这个常用功能做些什么来让TypeScript不争论吗?
UPD:一些测试让我创建了一个更接近所需的示例:
type Component<T> = React.Component<{}, {flag: T}>
const render = <T>(
instance: Component<T>,
cb: () => React.ReactNode
) => instance.state.flag ? cb() : '';
class Test extends React.Component<{}, {flag: boolean}> {
state = {flag: true};
render() {
const result = render(this, () => '');
return result;
}
inner = () => 'test';
}
这里的要点是外部render
函数是通用的,instance
类型取决于泛型参数,因此TypeScript无法替换正确的参数来代替T
。是否有可能在不失去类型安全的情况下帮助他?
这里的问题似乎是渲染函数中实例参数的类型推断。
让我们来看看
type RenderF = (
instance: React.Component<any, any>,
cb: () => React.ReactNode) => React.ReactNode;
const render: RenderF = (
instance: React.Component<{}, {flag: boolean}>,
cb: () => React.ReactNode
) => instance.state.flag ? cb() : null;
class Test extends React.Component<{}, {flag: boolean}> {
state = {flag: true};
render() { return render(this, () => null) }
}
type RenderF = (
instance: any, // <-----
cb: () => React.ReactNode) => React.ReactNode;
const render: RenderF = (
instance: React.Component<{}, {flag: boolean}>,
cb: () => React.ReactNode
) => instance.state.flag ? cb() : null;
class Test extends React.Component<{}, {flag: boolean}> {
state = {flag: true};
render() { return render(this, () => null) }
}
UPD
如果您不想在实例参数中放松类型安全性,则只能在新类型中指定所需的内容
interface FlagComponent {
state: { flag: boolean }
}
type RenderF = (
instance: FlagComponent,
cb: () => React.ReactNode) => React.ReactNode;
const render: RenderF = (
instance: React.Component<{}, {flag: boolean}>,
cb: () => React.ReactNode
) => instance.state.flag ? cb() : null;
class Test extends React.Component<{}, {flag: boolean}> {
state = {flag: true};
render() { return render(this, () => null) }
}