Question

我在React中编写一个组件，希望接收一个组件，该组件拥有一个特定字段onPropChange，可以通过ref访问，作为prop。

/* @flow */
import * as React from 'react';

type onPropChangeObject<Props> = {
    [key: $Keys<Props>]: (newValue: any) => void
}

declare class PropWatchableComponent<DefaultProps, Props: Object, State> 
    extends React.Component<DefaultProps, Props, State> 
{
    onPropChange?: onPropChangeObject<Props>;
}

但是最新版本的Flow（0.39.0）as seen here

中的类型检查失败并出现多个错误

8: declare class PropWatchableComponent<DefaultProps, Props: Object, State> extends React.Component<DefaultProps, Props, State> {   ^ undefined. Did you forget to declare some incompatible instantiation of `DefaultProps`?. This type is incompatible with
8: declare class PropWatchableComponent<DefaultProps, Props: Object, State> extends React.Component<DefaultProps, Props, State> {   ^ some incompatible instantiation of `DefaultProps`
8: declare class PropWatchableComponent<DefaultProps, Props: Object, State> extends React.Component<DefaultProps, Props, State> {   ^ undefined. Did you forget to declare some incompatible instantiation of `State`?. This type is incompatible with
8: declare class PropWatchableComponent<DefaultProps, Props: Object, State> extends React.Component<DefaultProps, Props, State> {   ^ some incompatible instantiation of `State`
8: declare class PropWatchableComponent<DefaultProps, Props: Object, State> extends React.Component<DefaultProps, Props, State> {
                                        ^ DefaultProps. This type is incompatible with
8: declare class PropWatchableComponent<DefaultProps, Props: Object, State> extends React.Component<DefaultProps, Props, State> {
                                        ^ undefined. Did you forget to declare DefaultProps?
8: declare class PropWatchableComponent<DefaultProps, Props: Object, State> extends React.Component<DefaultProps, Props, State> {
                                                                     ^ State. This type is incompatible with
8: declare class PropWatchableComponent<DefaultProps, Props: Object, State> extends React.Component<DefaultProps, Props, State> {
                                                                     ^ undefined. Did you forget to declare State?

所有关于undefined的讨论是什么？我明确声明DefaultProps和State作为类型参数。我忘记了什么？

Answer 1

看到这一点，你应该使用interface代替`class'。

https://flowtype.org/try/#0PQKgBAAgZgNg9gdzCYAoAlgWwA5wE4AuYASgKYCGAxkVHnJmAOR4XWMDcqqBAntqWDgA7AAp1sAYQAW5IQHNSAeQBGAK1LUAPGLjYAzgC4wK9dQB8YALxgA3qjBgA2gGtSPIwBIA0m73bxemYAukYAFEKkCABq5DAArqRGsjwAlFYWAG5w6AAmqAC+XOhCBKR4UFQCOtgA6uQElDLKMKQS9LgRJf66hsZqGgQWdg4AkNgBRtV6nA72DoKi4tKyCgD8RsLVy-JK-VpTZpyF86hQcULU6MJgCPWNWzI7eqE1eOTY-DlGEjDken7VOoNJotNo4YSkLomAZmMxpGyFVCUX7-MAAZVucjBHUhRFIAA9SkIcnoSKwCAA6bEQkq2OabJaPBQbRa6bYKaFaTmDKx00bjXRhchpSwWSjCPRwFoU+ByUKMKgEK5CRgAGjAwrmhURt2BDxWpGeGPIWPaNIIKSAA

声明一个扩展另一个多态类的多态类

1 个答案: