<!DOCTYPE html><html><script src="https://unpkg.com/react@16/umd/react.production.min.js"></script><script src="https://unpkg.com/react-dom@16/umd/react-dom.production.min.js"></script><script src="https://unpkg.com/babel-standalone@6.15.0/babel.min.js"></script><body> <div id="root"></div><script type="text/babel">class Hello extends React.Component { constructor(props) { super(props); this.state = { myStr: "Initial state" }; this.switch_func = this.switch_func.bind(this); } switch_func = () => { // the setState if commented ...the initial state of myStr is executed ..meaning the function is called however the setState method doesnt work . Can anyone tell why this is happening? this.setState({ myStr: "yess"}); return ( <div> <h3>{this.state.myStr}</h3> </div> ); } render() { return ( <div> <h1>Hello, world!</h1> {this.switch_func()} </div> ); }}ReactDOM.render(<Hello />, document.getElementById('root'))</script></body></html>即使在綁定了函數(shù) switch_func 之后，它也不會(huì)被執(zhí)行，并且 myStr 的狀態(tài)保持與初始化時(shí)相同。請(qǐng)幫助解決編碼未能顯示所需結(jié)果的地方。誰(shuí)能告訴為什么 setState 方法在這里不起作用？所需的輸出是 myStr 的狀態(tài)更改為 - “是的，它是四個(gè)！”class MyClass extends React.Component { constructor(props) { super(props); this.state = {myStr: "Initial state"}; this.switch_func = this.switch_func.bind(this); } switch_func = ()=> { this.setState({myStr: "In function"}); switch (1 + 3) { case 2 + 2: this.setState({ myStr: "Yes its four!"}); break; default: this.setState({ myStr: "Oops! default"}); } return( <div> <h3>{this.state.myStr}</h3> </div> ); }
我正在嘗試調(diào)用 switch_func 函數(shù)。但不知何故無法得到想要的結(jié)果
qq_笑_17
2022-07-21 10:32:19
