react-子组件与父组件

子组件改变父组件的state
class Parent extends Component{
state = {
msg: 'start'
};
render() {
return <Child_1 msg={this.state.msg} />;
}
}
class Child_1 extends Component{
render() {
return <p>{this.props.msg}</p>
}
}

父组件改变子组件的内容
class Parent extends Component{
render() {
return <Child_1 inputPlaceholder="请输入" />;
}
}
class Child_1 extends Component{
render() {
const { inputPlaceholder } = this.props;
return <input placeholder={inputPlaceholder} />
}
}

父组件调用子组件的方法
方法一：
import React, {Component} from 'react';
export default class Parent extends Component {
render() {
return(
<div>
<Child onRef={this.onRef} />
<button onClick={this.click} >click</button>
</div>
)
}
onRef = (ref) => {
this.child = ref
}
click = (e) => {
this.child.myName()
}
}
class Child extends Component {
componentDidMount(){
this.props.onRef(this)
}
myName = () => alert('xiaohesong')
render() {
return ('wo')
}
}
方法二：
import React, {Component} from 'react';
export default class Parent extends Component {
click = () => {
this.divRef.myName();
}
render() {
return(
<div ref＝{refs => this.divRef =refs}> />
)
}
}
class Child extends Component {
myName = () => alert('xiaohesong')
}

子组件调用父组件的方法
class Parent extends Component{
onChange = (value) => {
...
}
}
class Child extends Component{
this.props.onChange(value);
}

父组件引用多个相同子组件，分别向该子组件传值的方法
class Parent extends Component{
onChange = (value) => {
...
}
render() {
return (
<div>
<Child showStatus={0} />
<Child showStatus={1} />
</div>
)
}
}
class Child extends Component{
componentDidMount() {
const showStatus = this.props.showStatus;
if (showStatus === 0) {
} else if (showStatus === 1) {
}
}
}