我已经实现了React Context API,我试图通过子组件内的onClick函数更新Provider中定义的状态。
这是我到目前为止所做的,在我的App.js中:
import { createContext } from 'react';
const MyContext = React.createContext();
export class MyProvider extends Component {
state = {
currPrj: ''
}
handleBtnClick = prjCode => {
this.setState({
currPrj: prjCode
})
}
render() {
return(
<MyContext.Provider value={{
state: this.state
}}>
{this.props.children}
</MyContext.Provider>
)
}
}
export const MyComsumer = MyContext.Consumer;
我的孩子组件里面有:
import React, { Component } from "react";
import { BrowserRouter as Router, Route, Link } from "react-router-dom";
import { MyComsumer } from "../../index";
export class ProjectCard extends Component {
constructor(props) {
super(props);
this.state = {
// currPrj: ''
};
}
render() {
return (
<MyComsumer>
{(context) => (
<div className="card card-project">
<p>{context.state.currPrj}</p>
<div className="content">
<div className="author">
<Link to={ `projects/${this.props.code}/detail/info` } onClick={() => handleBtnClick(this.props.code) }>
<h4 className="title">
{this.props.title}
</h4>
</Link>
</div>
</div>
)}
</MyComsumer>
);
}
}
export default ProjectCard;
这样我得到以下错误
Failed to compile
./src/components/ProjectCard/ProjectCard.jsx
Line 32: 'handleBtnClick' is not defined no-undef
Search for the keywords to learn more about each error.
我不明白为什么,因为:
<p>{context.state.currPrj}</p>
没有错误......
另外,this.props.code是否正确传递给函数?
非常感谢。
存在linter错误,因为没有定义handleBtnClick
。它是另一个类的方法,而不是独立的函数。
它在上下文消费者功能的范围内不可用。如果消费者应该更新上下文,则updater函数应该是上下文的一部分:
<MyContext.Provider value={{
state: this.state,
update: this.handleBtnClick
}}>
使用如下:
context.update(this.props.code)
你可以这样说:
我的小提琴:https://jsfiddle.net/leolima/ds0o91xa/1/
class Parent extends React.Component {
sayHey(son) {
alert('Hi father, this is son '+son+' speaking');
}
render() {
const children = React.Children.map(this.props.children, (child, index) => {
return React.cloneElement(child, {
someFunction: () => this.sayHey(index)
});
});
return (<div>
<b>Parent</b>
<hr />
{children}
</div>);
}
}
class Child extends React.Component {
render() {
return <div>
<button onClick={() => this.props.someFunction()}>Child</button>
</div>;
}
}
ReactDOM.render(
<Parent>
<Child />
<Child />
</Parent>,
document.getElementById('container')
);
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.6.3/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.6.3/umd/react-dom.production.min.js"></script>
<div id="container">
</div>