[React]属性和状态

版权声明：本文为博主原创文章，转载请注明出处，谢谢。 https://blog.csdn.net/FreeeLinux/article/details/78768664

属性和含义和用法(props)

三种赋值方法

1.

   var style = {
        color: "red",
        border: "1px solid #000",
    };

    var HelloWorld = React.createClass({
        render: function () {
            return <p>Hello, {this.props.name ? this.props.name : "World"}</p>;
        }
    });


    var HelloUniverse = React.createClass({
        getInitialState: function () {
            return {name: ''};
        },
        handleChange: function (event) {
            this.setState({name: event.target.value});
        },
        render: function () {
            return <div>
                <HelloWorld name={this.state.name}></HelloWorld>
                <br/>
                <input type="text" onChange={this.handleChange}/>
            </div>
        }
    });
    ReactDOM.render(
            <div style={style}><HelloUniverse></HelloUniverse></div>
        , document.body)

2.

    var style = {
        color: "red",
        border: "1px solid #000",
    };

    var HelloWorld = React.createClass({
        render: function () {
            return <p>Hello, {this.props.name1 + ' ' + this.props.name2}</p>;
        }
    });


    var HelloUniverse = React.createClass({
        getInitialState: function () {
            return {
                name1: 'Tim',
                name2: 'John'
            };
        },
        handleChange: function (event) {
            this.setState({name1: event.target.value});
        },
        render: function () {
            return <div>
                <HelloWorld {...this.state}></HelloWorld>
                <br/>
                <input type="text" onChange={this.handleChange}/>
            </div>
        }
    });
    ReactDOM.render(
            <div style={style}><HelloUniverse></HelloUniverse></div>
        , document.body)

3.setProps形式：通过组件更新属性，不能在组件内部中修改属性的，因为会违背组件设计原则（尽量避免）

    var HelloWorld = React.createClass({
        render: function(){
            return <p>Hello, {this.props.name}</p>
        }
    });
    var instance = ReactDOM.render(<HelloWorld></HelloWorld>, document.body);
    instance.setProps({name: 'wilcohuang'});

状态的含义和用法(state)

• getInitialState: 初始化每个实例特有和居状态
• setState: 更新组件状态，setState->diff算法->(如果有变化)->更新DOM

属性和状态对比

相同点：

• 都是纯JS对象
• 都会触发render更新
• 都具有确定性

-	属性	状态
能否从父组件获取初始值	yes	no
能否由父组件修改	yes	no
能否在组件内部设置默认值	yes	yes
能否在组件内部修改	no	yes
能否设置子组件的初始值	yes	no
能否修改子组件的值	yes	no

组件在运行时需要修改的数据就要状态。

属性和状态实战

1. 分析构成项目的组件
2. 分析组件的关系及数据传递
3. 实际编写代码

var Content = React.createClass({
        render: function () {
            return <p>{this.props.selectName}</p>;
        },
    });
    var Comment = React.createClass({
        getInitialState: function () {
            return {
                names: ['Tim', 'John', 'Hank'],
                selectName: '',
            };
        },
        handleSelect: function () {
            this.setState({selectName: event.target.value});
        },
        render: function () {
            var options = [];
            for (var option in this.state.names) {
                options.push(<option value={this.state.names[option]}>{this.state.names[option]}</option>);
            }
            return <div>
                <select onChange={this.handleSelect}>
                    {options}
                </select>
                <Content selectName={this.state.selectName}></Content>
            </div>;
        },
    });
    ReactDOM.render(<Comment></Comment>, document.body);

    var Content = React.createClass({
        getInitialState: function () {
            return {
//                text: "reply To: " + this.props.selectName,    //写在这里是错误的，getInitialState相当于构造函数，如果selectName改变，这里不能更新
                inputText: "",
            };
        },
        handleChange: function (event) {
            this.setState({inputText: event.target.value});
        },
        handleSubmit: function () {
            console.log('reply to ' + this.props.selectName + "\n" + this.state.inputText);
        },
        render: function () {
            return <div>
                <textarea onChange={this.handleChange} placeholder="please enter something..."></textarea>
                <button onClick={this.handleSubmit}>submit</button>
            </div>;
        },
    });
    var Comment = React.createClass({
        getInitialState: function () {
            return {
                names: ['Tim', 'John', 'Hank'],
                selectName: '',
            };
        },
        handleSelect: function () {
            this.setState({selectName: event.target.value});
        },
        render: function () {
            var options = [];
            for (var option in this.state.names) {
                options.push(<option value={this.state.names[option]}>{this.state.names[option]}</option>);
            }
            return <div>
                <select onChange={this.handleSelect}>
                    {options}
                </select>
                <Content selectName={this.state.selectName}></Content>
            </div>;
        },
    });
    ReactDOM.render(<Comment></Comment>, document.body);