使用reactjs和typescript的typesafe select onChange事件 [英] typesafe select onChange event using reactjs and typescript
本文介绍了使用reactjs和typescript的typesafe select onChange事件的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我已经弄清楚了如何使用对事件的丑陋转换将事件处理程序绑定到SELECT元素上.
I have figured out how to tie up an event handler on a SELECT element using an ugly cast of the event to any.
是否可以通过类型安全的方式检索值而无需强制转换为任何值?
Is it possible to retrieve the value in a type-safe manner without casting to any?
import React = require('react');
interface ITestState {
selectedValue: string;
}
export class Test extends React.Component<{}, ITestState> {
constructor() {
super();
this.state = { selectedValue: "A" };
}
change(event: React.FormEvent) {
console.log("Test.change");
console.log(event.target); // in chrome => <select class="form-control" id="searchType" data-reactid=".0.0.0.0.3.1">...</select>
// Use cast to any works but is not type safe
var unsafeSearchTypeValue = ((event.target) as any).value;
console.log(unsafeSearchTypeValue); // in chrome => B
this.setState({
selectedValue: unsafeSearchTypeValue
});
}
render() {
return (
<div>
<label htmlFor="searchType">Safe</label>
<select className="form-control" id="searchType" onChange={ e => this.change(e) } value={ this.state.selectedValue }>
<option value="A">A</option>
<option value="B">B</option>
</select>
<h1>{this.state.selectedValue}</h1>
</div>
);
}
}
推荐答案
由于将我的类型升级为反应0.14.43(我不确定确切何时引入),因此React.FormEvent类型现在是通用类型,因此将其删除需要演员.
Since upgrading my typings to react 0.14.43 (I'm not sure exactly when this was introduced), the React.FormEvent type is now generic and this removes the need for a cast.
import React = require('react');
interface ITestState {
selectedValue: string;
}
export class Test extends React.Component<{}, ITestState> {
constructor() {
super();
this.state = { selectedValue: "A" };
}
change(event: React.FormEvent<HTMLSelectElement>) {
// No longer need to cast to any - hooray for react!
var safeSearchTypeValue: string = event.currentTarget.value;
console.log(safeSearchTypeValue); // in chrome => B
this.setState({
selectedValue: safeSearchTypeValue
});
}
render() {
return (
<div>
<label htmlFor="searchType">Safe</label>
<select className="form-control" id="searchType" onChange={ e => this.change(e) } value={ this.state.selectedValue }>
<option value="A">A</option>
<option value="B">B</option>
</select>
<h1>{this.state.selectedValue}</h1>
</div>
);
}
}
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