在React中使用for循环和切换案例来动态渲染不同的组件 [英] Using for loops and switch cases in React to dynamically render different components

问题描述

我正在尝试使用React JSX中的switch case有条件地渲染组件.我正在尝试构建从特定json结构读取并呈现数据的内容.由于可以有许多不同的组件和数据，因此我尝试动态呈现它.请参阅下面的代码，我没有收到任何错误，但是组件没有得到渲染.在我的html中，我只能看到.这意味着循环无法正常工作.我尝试在香草JS中使用相同的循环，并且可以正常工作.

I am trying to render components conditionally using switch case in React JSX. I am trying to build something that reads from a specific json structure and renders the data. Since there can be many different components and data, I am trying to render it dynamically. See my code below, I am not getting any errors but the components aren't getting rendered. Inside my html , I can only see . This means the loop isn't working. I tried using the same loop in vanilla JS and it works.

var myPackage = [{
    sectionInfo:[{
        elementType: 1,
        text: "This is text from element type 1"
    }]
},
{
    sectionInfo:[{
        elementType: 2,
        text: "This is text from element type 2"
    }]
}];
var App = React.createClass({

    render: function(){
        var elements = [];
        elements = myPackage.map(function(myObj){
            myObj.sectionInfo.map(function(myObj1){
                switch(myObj1.elementType){
                    case 1: return(
                                <Component1 text = {myObj1.text}/>
                            );
                            break;
                    case 2: return(
                                <Component2 text = {myObj1.text}/>
                            )
                            break;      
                }
            })
        });
        return(
            <div className="App">
                {elements}
            </div>
        )
    }
});
var Component1 = React.createClass({
    render:function(){
        return(
            <div className = "element1">
                {this.props.text}
            </div>
        )
    }
});
var Component2 = React.createClass({
    render:function(){
        return(
            <div className = "element2">
                {this.props.text}
            </div>
        )
    }
});
ReactDOM.render(<App/>,document.getElementById('container'));

在代码中做了一些补充，现在我面临一个新问题.这是新代码:

Made a few additions to the code, and now I am facing a new problem. Here is the new code:

var App = React.createClass({

        render: function(){
            var elements = [];
            elements = myPackage.map(function(myObj){
                return(
                       <div>
                           myObj.sectionInfo.map(function(myObj1){
                           switch(myObj1.elementType){
                           case 1: return(
                                    <Component1 text = {myObj1.text}/>
                                );
                                break;
                           case 2: return(
                                    <Component2 text = {myObj1.text}/>
                                )
                                break;      
                        }
                        }
                  </div>
                )
                });
        return(
            <div className="App">
                {elements}
            </div>
        )
    }
});

我想每次在div中进行渲染.因此，如果一个部分包含3个以上的元素，则所有3个元素都必须在div内.

I want to render each time inside a div. So that if one section has more than 3 elements, then all 3 must be inside a div.

推荐答案

您应该从第一个.map返回值，如果是内部.map

You should return value from first .map, in your case it is result from inner .map

var elements = myPackage.map(function(myObj){
  return myObj.sectionInfo.map(function(myObj1) {
     // ...  
  });
});

更新:

根据您的新更新，您可以像这样更改代码

Based on your new update, you can change your code like this

var App = React.createClass({

  section: function(myObj, parentIndex) {
    return myObj.sectionInfo.map(function(myObj1, index) {
      const key = parentIndex + '.' + index;

      switch(myObj1.elementType) {
        case 1:
          return <Component1 text = {myObj1.text} key={ key } />
        case 2:
          return <Component2 text = {myObj1.text} key={ key } />
      }
    });
  },

  render: function() {
    var elements = myPackage.map(function(myObj) {
      return <div>
        { this.section(myObj, index) }
      </div>
    }, this);

    return <div className="App">
     { elements }
    </div>;
  }
});

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