将它绑定到React中的嵌套函数

Question

this在处理嵌套函数时如何绑定到React组件？

这是一个骨架的例子.function2嵌套的原因是您可以访问中定义的变量function1

class View extends Component{

    constructor(props){
        this.function1 = this.function1.bind(this);

        this.state = {
            a = null;
        }
    }

    componentDidMount(){
        function1();
    }

    function1(){
        console.log(this); //will show the component correctly

        var param1 = 10;

        //call a second function that's defined inside the first function
        function2();

        function function2(){
            console.log(this); //undefined

            var a = param1*2;

            this.setState({ a : a}); //won't work because this is undefined
        }
    }

    render(){
        return(
            <div>
                <p> Hello </p>
            </div>
        )
    }
}

Answer 1

为什么不使用箭头功能？这将确保this正确引用.我假设你可以使用ES6.

function1 = () => {
    console.log(this);

    var param1 = 10;

    const function2 = () => {
      console.log(this);

      var a = param1*2;

      this.setState({ a }); 
    }

    function2(); // inkove the function
}

或者,如果您只想使用ES5,那么这也可以

function1() {
    console.log(this);

    var param1 = 10;

    function function2() {
      console.log(this);

      var a = param1*2;

      this.setState({ a }); 
    }

    function2.bind(this)() // to invoke the function
}