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60 lines
1.9 KiB
60 lines
1.9 KiB
8 years ago
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---
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id: expose-component-functions-zh-CN
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title: 暴露组件函数
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layout: tips
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permalink: tips/expose-component-functions-zh-CN.html
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prev: communicate-between-components-zh-CN.html
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next: children-undefined-zh-CN.html
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---
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这是另外一种组件[通信的方法](/react/tips/communicate-between-components.html)：在子组件中暴露出一个方法，可以让父组件去调。
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让我们看看这个todos的列表，在点击的时候就会被移除。如果只剩下最后一个未完成的待办事项，就执行animate函数：
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```js
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var Todo = React.createClass({
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render: function() {
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return <div onClick={this.props.onClick}>{this.props.title}</div>;
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},
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//this component will be accessed by the parent through the `ref` attribute
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animate: function() {
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console.log('Pretend %s is animating', this.props.title);
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}
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});
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var Todos = React.createClass({
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getInitialState: function() {
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return {items: ['Apple', 'Banana', 'Cranberry']};
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},
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handleClick: function(index) {
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var items = this.state.items.filter(function(item, i) {
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return index !== i;
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});
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this.setState({items: items}, function() {
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if (items.length === 1) {
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this.refs.item0.animate();
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}
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}.bind(this));
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},
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render: function() {
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return (
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<div>
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{this.state.items.map(function(item, i) {
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var boundClick = this.handleClick.bind(this, i);
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return (
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<Todo onClick={boundClick} key={i} title={item} ref={'item' + i} />
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);
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}, this)}
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</div>
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);
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}
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});
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ReactDOM.render(<Todos />, mountNode);
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```
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当然，你也可以通过在`todo`组件中的prop传递`isLastUnfinishedItem`，来让子组件在 `componentDidUpdate`中判断是否它是最后一个，来执行animate函数；但是，如果你通过不同的props值来控制的不同的动画，到最后可能会变得很混乱。
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