Reactjs组件的异步呈现

Question

我想在完成ajax请求后渲染我的组件.

您可以在下面看到我的代码

var CategoriesSetup = React.createClass({

    render: function(){
        var rows = [];
        $.get('http://foobar.io/api/v1/listings/categories/').done(function (data) {
            $.each(data, function(index, element){
                rows.push(<OptionRow obj={element} />);
            });
           return (<Input type='select'>{rows}</Input>)

        })

    }
});

但我得到下面的错误,因为我在我的ajax请求的done方法内返回渲染.

Uncaught Error: Invariant Violation: CategoriesSetup.render(): A valid ReactComponent must be returned. You may have returned undefined, an array or some other invalid object.

有没有办法在开始渲染之前等待我的ajax请求结束？

Answer 1

有两种方法可以处理这个问题,您选择哪种方法取决于哪个组件应该拥有数据和加载状态.

1. 将Ajax请求移动到父级并有条件地呈现组件:

   var Parent = React.createClass({
     getInitialState: function() {
       return { data: null };
     },
   
     componentDidMount: function() {
       $.get('http://foobar.io/api/v1/listings/categories/').done(function(data) {
         this.setState({data: data});
       }.bind(this));
     },
   
     render: function() {
       if (this.state.data) {
         return <CategoriesSetup data={this.state.data} />;
       }
   
       return <div>Loading...</div>;
     }
   });
   

2. 将Ajax请求保留在组件中,并在加载时有条件地呈现其他内容:

   var CategoriesSetup = React.createClass({
     getInitialState: function() {
       return { data: null };
     },
   
     componentDidMount: function() {
       $.get('http://foobar.io/api/v1/listings/categories/').done(function(data) {
         this.setState({data: data});
       }.bind(this));
     },
   
     render: function() {
       if (this.state.data) {
         return <Input type="select">{this.state.data.map(this.renderRow)}</Input>;
       }
   
       return <div>Loading...</div>;
     },
   
     renderRow: function(row) {
       return <OptionRow obj={row} />;
     }
   });
   

Answer 2

组件异步呈现的基本示例如下：

import React                from 'react';
import ReactDOM             from 'react-dom';        
import PropTypes            from 'prop-types';

export default class YourComponent extends React.PureComponent {
    constructor(props){
        super(props);
        this.state = {
            data: null
        }       
    }

    componentDidMount(){
        const data = {
                optPost: 'userToStat01',
                message: 'We make a research of fetch'
            };
        const endpoint = 'http://example.com/api/phpGetPost.php';       
        const setState = this.setState.bind(this);      
        fetch(endpoint, {
            method: 'POST',
            body: JSON.stringify(data)
        })
        .then((resp) => resp.json())
        .then(function(response) {
            setState({data: response.message});
        });
    }

    render(){
        return (<div>
            {this.state.data === null ? 
                <div>Loading</div>
            :
                <div>{this.state.data}</div>
            }
        </div>);
    }
}