如何在ReactJS中将数据从子组件传递到其父组件？

• Z时代
• 2024-01-10
• 分类：问答

我正在尝试将数据从子组件发送到其父组件，如下所示：

const ParentComponent = React.createClass({
    getInitialState() {
        return {
            language: '',
        };
    },
    handleLanguageCode: function(langValue) {
        this.setState({language: langValue});
    },
    render() {
         return (
                <div className="col-sm-9" >
                    <SelectLanguage onSelectLanguage={this.handleLanguage}/> 
                </div>
        );
});

这是子组件：

export const SelectLanguage = React.createClass({
    getInitialState: function(){
        return{
            selectedCode: '',
            selectedLanguage: '',
        };
    },
    handleLangChange: function (e) {
        var lang = this.state.selectedLanguage;
        var code = this.state.selectedCode;
        this.props.onSelectLanguage({selectedLanguage: lang});   
        this.props.onSelectLanguage({selectedCode: code});           
    },
    render() {
        var json = require("json!../languages.json");
        var jsonArray = json.languages;
        return (
            <div >
                <DropdownList ref='dropdown'
                    data={jsonArray} 
                    value={this.state.selectedLanguage}
                    caseSensitive={false} 
                    minLength={3}
                    filter='contains'
                    onChange={this.handleLangChange} />
            </div>            
        );
    }
});

我需要的是由用户在父组件中获取选定的值。我收到此错误：

Uncaught TypeError: this.props.onSelectLanguage is not a function

谁能帮我发现问题？

PS子组件正在从json文件创建一个下拉列表，并且我需要该下拉列表来显示json数组的两个元素彼此相邻（例如：“ aaa，english”是首选！）

{  
   "languages":[  
      [  
         "aaa",
         "english"
      ],
      [  
         "aab",
         "swedish"
      ],
}

回答：

这应该工作。在发送回道具时，您将其作为对象发送，而不是作为值发送，或者将其用作父组件中的对象。其次，您需要格式化json对象，使其包含名称值对以及使用valueField和textField属性DropdownList

<div className="col-sm-9">
     <SelectLanguage onSelectLanguage={this.handleLanguage} /> 
</div>

handleLangChange = () => {
    var lang = this.dropdown.value;
    this.props.onSelectLanguage(lang);            
}

考虑到从v16.0起不推荐使用React.createClass，最好继续扩展来创建React组件React.Component。使用这种语法将数据从子组件传递到父组件看起来像

父组

class ParentComponent extends React.Component {
    state = { language: '' }
    handleLanguage = (langValue) => {
        this.setState({language: langValue});
    }
    render() {
         return (
                <div className="col-sm-9">
                    <SelectLanguage onSelectLanguage={this.handleLanguage} /> 
                </div>
        )
     }
}

子组

var json = require("json!../languages.json");
var jsonArray = json.languages;
export class SelectLanguage extends React.Component {
    state = {
            selectedCode: '',
            selectedLanguage: jsonArray[0],
        }
    handleLangChange = () => {
        var lang = this.dropdown.value;
        this.props.onSelectLanguage(lang);            
    }
    render() {
        return (
            <div>
                <DropdownList ref={(ref) => this.dropdown = ref}
                    data={jsonArray} 
                    valueField='lang' textField='lang'
                    caseSensitive={false} 
                    minLength={3}
                    filter='contains'
                    onChange={this.handleLangChange} />
            </div>            
        );
    }
}

使用createClassOP在其答案中使用的语法

const ParentComponent = React.createClass({
    getInitialState() {
        return {
            language: '',
        };
    },
    handleLanguage: function(langValue) {
        this.setState({language: langValue});
    },
    render() {
         return (
                <div className="col-sm-9">
                    <SelectLanguage onSelectLanguage={this.handleLanguage} /> 
                </div>
        );
});

var json = require("json!../languages.json");
var jsonArray = json.languages;
export const SelectLanguage = React.createClass({
    getInitialState: function() {
        return {
            selectedCode: '',
            selectedLanguage: jsonArray[0],
        };
    },
    handleLangChange: function () {
        var lang = this.refs.dropdown.value;
        this.props.onSelectLanguage(lang);            
    },
    render() {
        return (
            <div>
                <DropdownList ref='dropdown'
                    data={jsonArray} 
                    valueField='lang' textField='lang'
                    caseSensitive={false} 
                    minLength={3}
                    filter='contains'
                    onChange={this.handleLangChange} />
            </div>            
        );
    }
});

{ 
"languages":[
    { 
    "code": "aaa", 
    "lang": "english" 
    }, 
    { 
    "code": "aab", 
    "lang": "Swedish" 
    }, 
  ] 
}

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