[英]What is the meaning of `Component<Props>` of react-native
I created a new react-native project recently, and I found the component syntax becoming export default class WelcomeScreen extends Component<Props>
that's different from export default class WelcomeScreen extends Component
before. 我最近创建了一个新的react-native项目,发现组件语法成为
export default class WelcomeScreen extends Component<Props>
,这与之前export default class WelcomeScreen extends Component
有所不同。
I thought it's replace the syntax of code of below 我以为它取代了下面代码的语法
constructor(props) {
super(props)
}
but after testing, I found I still have to ref props with the code above, so what's the exactly function of this syntax <Props>
? 但是经过测试后,我发现我仍然必须使用上面的代码来引用props,那么此语法
<Props>
的确切功能是什么?
Component<Props>
is syntax of Flow to check type of data on Props. Component<Props>
是Flow的语法,用于检查Props上的数据类型。 Flow infers types and tracks data as it moves through your code. 当数据在代码中移动时,Flow会推断类型并跟踪数据。
Example: 例:
// @flow
import * as React from 'react';
import { Text } from 'react-native';
type Props = {
bar: string, // this mean type data of bar is string and is required.
};
class MyComponent extends React.Component<Props> {
render() {
return <Text>{this.props.bar}</Text>;
}
}
Reference: 参考:
https://flow.org/en/ https://flow.org/en/
https://flow.org/en/docs/react/ https://flow.org/en/docs/react/
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