{"id":7028,"date":"2023-08-16T13:20:41","date_gmt":"2023-08-16T05:20:41","guid":{"rendered":"https:\/\/i007.vip:15443\/wordpress\/?p=7028"},"modified":"2023-08-16T13:20:41","modified_gmt":"2023-08-16T05:20:41","slug":"%e4%b8%80%e6%96%87%e8%ae%a9%e4%bd%a0%e4%b8%8d%e5%86%8d%e5%9b%b0%e6%83%91setstate%e4%b9%8bgetstate","status":"publish","type":"post","link":"https:\/\/i007.cc\/wordpress\/archives\/7028","title":{"rendered":"\u4e00\u6587\u8ba9\u4f60\u4e0d\u518d\u56f0\u60d1setState\u4e4bgetState"},"content":{"rendered":"
cc from<\/a><\/div>\n
<\/div>\n
React\u9ad8\u7ea7<\/div>\n
\u4e13\u680f\u6536\u5f55\u8be5\u5185\u5bb9<\/div>\n
10 \u7bc7\u6587\u7ae00 \u8ba2\u9605<\/div>\n
\u8ba2\u9605\u4e13\u680f<\/div>\n
\u6587\u7ae0\u76ee\u5f55<\/div>\n
setState \u7684\u7279\u70b9<\/div>\n
getState() \u83b7\u53d6\u6700\u65b0\u72b6\u6001\u503c<\/div>\n
\u5728\u9762\u8bd5\u4e2d\u6211\u4eec\u901a\u5e38\u4f1a\u88ab\u95ee\u5230\u6709\u5173 setState \u76f8\u5173\u7684\u95ee\u9898\u3002<\/div>\n
\u63a5\u4e0b\u6765\u6211\u4eec\u5148\u770b\u51e0\u4e2a\u793a\u4f8b\uff0c\u7136\u540e\u901a\u8fc7 \u6a21\u62df\u5b9e\u73b0 setState\u7684\u884c\u4e3a\u6765\u66f4\u52a0\u6df1\u523b\u7684\u7406\u89e3\u5b9e\u4f8b\u5f97\u51fa\u7684\u7ed3\u8bba\u3002<\/div>\n
<\/div>\n
setState \u7684\u7279\u70b9<\/div>\n
\u6279\u91cf\u6267\u884c\uff1a\u591akey\u4e00\u6b21\u6267\u884c\uff0c\u5bf9\u540c\u4e00\u4e2akey\u591a\u6b21\u64cd\u4f5c\u4f1a\u5408\u5e76\uff0c\u4f1a\u6267\u884c\u6700\u540e\u4e00\u6b21<\/div>\n
\u53ef\u80fd\u662f\u5f02\u6b65\u7684\uff08\u5982\u5728\u751f\u547d\u5468\u671f\u3001react\u5408\u6210\u4e8b\u4ef6\u4e2d\uff09<\/div>\n
\u5728\u5b9a\u65f6\u5668\u548c\u539f\u751f\u4e8b\u4ef6\u4e2d\uff0c\u5b83\u662f\u540c\u6b65\u7684\uff1b<\/div>\n
\u7531\u4e8e setState \u53ef\u80fd\u662f\u5f02\u6b65\u7684\uff0c\u5982\u679c\u8981\u7acb\u5373\u83b7\u53d6\u5230\u6700\u65b0\u7684\u503c\uff0c\u6709\u4e09\u79cd\u65b9\u5f0f\uff1a<\/div>\n
<\/div>\n
\u4f20\u51fd\u6570\u7ed9setState\uff0c \u6216\u8005\u5728\u7b2c\u4e8c\u4e2a\u53c2\u6570\u56de\u8c03\u51fd\u6570\u4e2d\u83b7\u53d6\u6700\u65b0\u503c<\/div>\n
\u5728\u5b9a\u65f6\u5668setTimeout\u4e2d<\/div>\n
\u5728\u539f\u751f\u4e8b\u4ef6\u4e2d\uff08\u8df3\u8fc7\u4e86react\u7684\u4e8b\u4ef6\u673a\u5236\uff09<\/div>\n
\u548b\u4e00\u770b\uff0c\u8fd8\u662f\u89c9\u5f97\u6bd4\u8f83\u7ed5\uff0c\u7ed3\u5408\u4ee5\u4e0a\u7279\u70b9\uff0c\u6211\u4eec\u6765\u770b\u51e0\u4e2a\u4f8b\u5b50<\/div>\n
<\/div>\n
\u591a\u6b21\u6267\u884c\u540c\u4e00\u4e2akey<\/div>\n
class App1 extends React.Component {<\/div>\n
\u00a0 state = { count: 1 }<\/div>\n
\u00a0 componentDidMount() {<\/div>\n
\u00a0 \u00a0 this.setState({ count: this.state.count++ })<\/div>\n
\u00a0 \u00a0 this.setState({ count: this.state.count + 1 })<\/div>\n
\u00a0 \u00a0 this.setState({ count: this.state.count + 2 })<\/div>\n
\u00a0 \u00a0 console.log(‘count1’, this.state.count); \/\/\u00a0 \uff1f\uff1f1<\/div>\n
\u00a0 \u00a0 \/\/ \u4f7f\u7528\u5b9a\u65f6\u5668<\/div>\n
\u00a0 \u00a0 \u00a0setTimeout(() => {<\/div>\n
\u00a0 \u00a0 \u00a0 console.log(‘count2’, this.state.count) \/\/ \uff1f\uff1f2<\/div>\n
\u00a0 \u00a0 })<\/div>\n
\u00a0 }<\/div>\n
\u00a0 handleClick = () => {<\/div>\n
\u00a0 \u00a0 this.setState(({ count }) => {<\/div>\n
\u00a0 \u00a0 \u00a0 console.log(‘count3’, count) \/\/ \uff1f\uff1f 3<\/div>\n
\u00a0 \u00a0 \u00a0 return { count: count + 1}<\/div>\n
\u00a0 \u00a0 })<\/div>\n
console.log(‘count4’, this.state.count) \/\/ ?? 4<\/div>\n
\u00a0 \u00a0 this.setState(({ count }) => {<\/div>\n
\u00a0 \u00a0 \u00a0 console.log(‘count5’, count) \/\/ \uff1f\uff1f5<\/div>\n
\u00a0 \u00a0 })<\/div>\n
\u00a0 }<\/div>\n
\u00a0 render() {<\/div>\n
\u00a0 \u00a0 return <div><\/div>\n
\u00a0 \u00a0 \u00a0 <p>count: {this.state.count}<\/p><\/div>\n
\u00a0 \u00a0 \u00a0 <button onClick={this.handleClick}>\u52a01<\/button><\/div>\n
\u00a0 \u00a0 <\/div><\/div>\n
\u00a0 }<\/div>\n
\u00a0}<\/div>\n
<\/div>\n
\u6211\u4eec\u601d\u8003\u4e0b\uff0c\u63a7\u5236\u53f01\uff0c 2 \u548c\u754c\u9762\u4e0a\u6e32\u67d3\u7684\u503c\u5206\u522b\u662f\u591a\u5c11\u5462\uff1f<\/div>\n
\u5f53\u70b9\u51fb\u6309\u94ae\u4e4b\u540e\uff0c\u63a7\u5236\u53f0 3\uff0c4, 5\u548c\u754c\u9762\u6e32\u67d3\u503c\u53c8\u5206\u522b\u662f\u591a\u5c11\uff1f<\/div>\n
<\/div>\n
count1: 2<\/div>\n
count2: 4<\/div>\n
\u754c\u9762\u663e\u793a\uff1a4<\/div>\n
\u70b9\u51fb\u4e00\u6b21<\/div>\n
count4: 4<\/div>\n
count3: 4<\/div>\n
count5: 5<\/div>\n
\u754c\u9762\u663e\u793a\uff1a6<\/div>\n
\u4f60\u5206\u6790\u5bf9\u4e86\u5417\uff1f<\/div>\n
\u6211\u4eec\u9996\u5148\u7406\u8bba\u5206\u6790\u4e00\u4e0b\uff0c\u7b2c\u4e00\u6b21\u6267\u884c\u65f6\uff0c\u540c\u4e00\u4e2akey \u591a\u6b21\u6267\u884c\u4f1a\u88ab\u5408\u5e76\u4e3a\u4e00\u6b21\uff0c\u5e76\u6267\u884c\u6700\u540e\u4e00\u6b21\uff0c\u56e0\u6b64\u6700\u7ec8\u5b9e\u9645\u6267\u884c\u7684\u662f<\/div>\n
<\/div>\n
this.state.count++<\/div>\n
this.setState({ count: this.state.count + 2 })<\/div>\n
<\/div>\n
\u6240\u4ee5\u754c\u9762\u4e0a\u7ed3\u679c\u663e\u793a\u4e3a 4 \uff0c\u53c8\u56e0\u4e3a setState \u53ef\u80fd\u662f\u5f02\u6b65\u7684\uff0c\u6211\u4eec\u5728 1 \u5904 \u8bfb\u53d6\u5230\u7684\u5b9e\u9645\u4e0a\u662f this.state.count++ \u4e4b\u540e\u7684\u503c\uff0c\u8fd9\u91cc\u9700\u8981\u6ce8\u610f\u7684\u662fthis.state.count++\u662f\u5bf9count\u672c\u8eab\u7684\u4e00\u79cd\u64cd\u4f5c\uff0c\u4e0d\u662f\u8d4b\u4e88\u65b0\u503c\u3002<\/div>\n
<\/div>\n
\u6211\u4eec\u70b9\u51fb\u4e00\u6b21\u540e\uff0c\u51fd\u6570\u4e2d\u6267\u884c\u4e86\u4e24\u6b21 setState\uff0c\u6267\u884c\u987a\u5e8f\u662fcount4: 4\uff0ccount3: 4\uff0ccount5: 5\uff1b\u5f53 setState \u63a5\u53d7\u56de\u8c03\u51fd\u6570\u65f6\uff0c\u53c2\u6570\u662f\u6700\u65b0\u7684 state \u503c\uff0c\u56de\u8c03\u4f1a\u88ab\u4e00\u4e00\u6267\u884c\uff0c\u56e0\u6b64\u5728\u7b2c\u4e00\u4e2a\u56de\u8c03\u51fd\u6570\u4e2d\u7684count \u4e3a 4\uff0c\u6267\u884c\u52a0\u4e00\u540e\uff0c\u7b2c\u4e8c\u4e2a\u56de\u8c03\u4e2d\u5c31\u662f 5, \u518d\u6267\u884c\u52a0\u4e00\uff0c\u6700\u7ec8\u754c\u9762\u663e\u793a6\u3002<\/div>\n
<\/div>\n
OK\uff0c\u6211\u4eec\u518d\u6765\u7a0d\u5fae\u53d8\u5316\u4e00\u70b9\u70b9\uff0c\u6211\u4eec\u52a0\u4e0a\u7b2c\u4e8c\u4e2a\u53c2\u6570\u56de\u6389\uff1a<\/div>\n
<\/div>\n
componentDidMount() {<\/div>\n
\u00a0 \u00a0 this.setState({ count: this.state.count++ })<\/div>\n
\u00a0 \u00a0 this.setState({ count: this.state.count + 1 }, () => {<\/div>\n
\u00a0 \u00a0 \u00a0 console.log(‘\u56de\u8c031’, this.state.count)<\/div>\n
\u00a0 \u00a0 })<\/div>\n
\u00a0 \u00a0 this.setState({ count: this.state.count + 2 }, () => {<\/div>\n
\u00a0 \u00a0 \u00a0 console.log(‘\u56de\u8c032’, this.state.count)<\/div>\n
\u00a0 \u00a0 })<\/div>\n
\u00a0 \u00a0 console.log(‘count1’, this.state.count)<\/div>\n
<\/div>\n
\u00a0 \u00a0 this.setState(({ count }) => {<\/div>\n
\u00a0 \u00a0 \u00a0 console.log(‘count2’, count)<\/div>\n
\u00a0 \u00a0 \u00a0 return { count: count + 1 }<\/div>\n
\u00a0 \u00a0 })<\/div>\n
<\/div>\n
\u00a0 \u00a0 this.setState({ count: this.state.count + 1 }, () => {<\/div>\n
\u00a0 \u00a0 \u00a0 console.log(‘\u56de\u8c033’, this.state.count)<\/div>\n
\u00a0 \u00a0 })<\/div>\n
\u00a0 \u00a0 console.log(‘count3’, this.state.count)<\/div>\n
\u00a0 \u00a0 setTimeout(() => {<\/div>\n
\u00a0 \u00a0 \u00a0 console.log(‘count4’, this.state.count)<\/div>\n
\u00a0 \u00a0 })<\/div>\n
<\/div>\n
\u5982\u679c\u4ed4\u7ec6\u7684\u540c\u5b66\uff0c\u4f1a\u53d1\u73b0\u8fd9\u91cc\u6709\u4e00\u4e2a\u7ec6\u8282\uff0c\u5982\u679c\u4e0d\u6ce8\u610f\uff0c\u7ed3\u679c\u5c31\u4f1a\u4e0d\u4e00\u6837\uff0c\u6211\u4eec\u770b\u4e0b\u6700\u7ec8\u7684\u6267\u884c\u987a\u5e8f\u548c\u7ed3\u679c\uff1a<\/div>\n
<\/div>\n
count1\uff1a 2<\/div>\n
count3\uff1a 2<\/div>\n
count2 \uff1a4<\/div>\n
\u56de\u8c031\uff1a 3<\/div>\n
\u56de\u8c032 \uff1a3<\/div>\n
\u56de\u8c033 \uff1a3<\/div>\n
count4 \uff1a3<\/div>\n
\u754c\u9762\u663e\u793a\u7ed3\u679c\uff1a3<\/div>\n
<\/div>\n
\u8fd9\u91cc\u9700\u8981\u7740\u91cd\u5206\u6790\u7684\u662f\u56de\u8c03\u4e2d\u6253\u5370\u7684\u503c\uff0c\u5728count2 \u6267\u884c\u5b8c\u4e4b\u540e count \u503c\u53d8\u4e3a\u4e865\uff0c\u63a5\u4e0b\u6765\u6267\u884c\u7684 this.setState({ count: this.state.count + 1 }, () => { console.log(‘\u56de\u8c033’, this.state.count) }) \u6ce8\u610f\uff0c\u8fd9\u91ccthis.state.count \u7684\u503c\u5176\u5b9e\u662f 2\uff0c\u6267\u884c\u5b8c\u4e4b\u540e\u7684\u7ed3\u679c\u5b9e\u9645\u662f 3\uff0c \u6240\u4ee5\u6700\u7ec8\u6211\u4eec\u5728\u56de\u8c03\u4e2d\u8bfb\u53d6\u7684 count \u90fd\u662f 3\u3002<\/div>\n
<\/div>\n
\u5982\u679c\u4e0a\u9762\u7684\u5206\u6790\u6ca1\u6709\u7406\u89e3\uff0c\u6ca1\u6709\u5173\u7cfb\uff0c\u73b0\u5728\u6211\u4eec\u6765\u68b3\u7406\u4e0b setState \u662f\u5982\u4f55\u66f4\u65b0\u72b6\u6001\u7684\uff0c\u5982\u4f55\u53bb\u83b7\u53d6\u6700\u7ec8\u7684 state\uff1f<\/div>\n
<\/div>\n
getState() \u83b7\u53d6\u6700\u65b0\u72b6\u6001\u503c<\/div>\n
setState(nextState, callback) \u5176\u5b9e\u505a\u7684\u4e8b\u60c5\u5f88\u7b80\u5355\uff0c\u5c31\u662f\u5c06\u63a5\u53d7\u7684 nextState \u548c callback \u5206\u522b\u6dfb\u52a0\u5230\u5f02\u6b65\u961f\u5217\u4e2d\uff1b<\/div>\n
<\/div>\n
\/\/ nextState \u53ef\u80fd\u662f\u5bf9\u8c61\u6216\u51fd\u6570<\/div>\n
setState(nextState, callback) {<\/div>\n
\/\/ \u6dfb\u52a0\u5f02\u6b65\u961f\u5217\u00a0 \u4e0d\u662f\u6bcf\u6b21\u90fd\u66f4\u65b0<\/div>\n
this.$updater.addCallback(callback)<\/div>\n
this.$updater.addState(nextState)<\/div>\n
}<\/div>\n
<\/div>\n
\u8fd9\u91cc\u6211\u4eec\u5148\u4e0d\u8bb2 setState \u7684\u66f4\u65b0\u5177\u4f53\u8fc7\u7a0b\uff0c\u5c06\u5728 \u4e00\u6587\u8ba9\u4f60\u4e0d\u518d\u56f0\u60d1setState\u4e4b\u539f\u7406\u5256\u6790\u548c\u624b\u5199\uff08\u4e0b\uff09\u4e2d\u8be6\u7ec6\u4ecb\u7ecd\u3002<\/div>\n
<\/div>\n
\u7ec4\u4ef6\u7684\u66f4\u65b0\u548c\u72b6\u6001\u7684\u6536\u96c6\u7b49\u90fd\u662fupdater\u4ee3\u7406\u6267\u884c\u7684\uff0c\u6211\u4eec\u6765\u5b9a\u4e49\u4e00\u4e2a Updater , \u4e3b\u8981\u5b9e\u73b0addCallback\u3001addState \u529f\u80fd\u3002<\/div>\n
<\/div>\n
class Updater{<\/div>\n
constructor(instance){<\/div>\n
this.instance = instance \/\/ \u7ec4\u4ef6\u5b9e\u4f8b<\/div>\n
this.pendingStates = [] \/\/ \u5f85\u5904\u7406\u72b6\u6001\u6570\u7ec4<\/div>\n
this.pendingCallbacks = [] \/\/ \u5f85\u5904\u7406\u56de\u8c03\u6570\u7ec4<\/div>\n
this.isPending = false<\/div>\n
}<\/div>\n
addState(nextState) {<\/div>\n
if (nextState) {<\/div>\n
\/\/ \u653e\u5165\u66f4\u65b0\u961f\u5217<\/div>\n
this.pendingStates.push(nextState)<\/div>\n
\/\/ \u5982\u679c\u5f53\u524d\u961f\u5217\u6ca1\u6709\u5de5\u4f5c\u5219\u76f4\u63a5\u66f4\u65b0<\/div>\n
if (!this.isPending) {<\/div>\n
this.emitUpdate() \/\/\u00a0 \u8fd9\u91cc\u7701\u7565\u5b83\u7684\u5b9e\u73b0\u3002\u3002\u3002\u3002<\/div>\n
}<\/div>\n
}<\/div>\n
}<\/div>\n
addCallback(callback) {<\/div>\n
if (_.isFn(callback)) {<\/div>\n
this.pendingCallbacks.push(callback)<\/div>\n
}<\/div>\n
}<\/div>\n
}<\/div>\n
<\/div>\n
\u53ef\u4ee5\u770b\u5230\uff0c\u8fd8\u662f\u7b80\u5355\u7684\u8fdb\u884c\u4e86\u5b58\u50a8\uff0c\u8fd9\u91cc\u4f1a\u5148\u53bb\u5224\u65ad\u5f53\u524d\u961f\u5217\u662f\u5426\u7a7a\u95f2\uff0c\u5982\u679c\u6ca1\u6709\u5de5\u4f5c\uff0c\u5219\u76f4\u63a5\u66f4\u65b0\u3002\u5728\u771f\u6b63\u53bb\u6267\u884c\u66f4\u65b0\u65f6\uff0c\u901a\u8fc7\u904d\u5386\u8fd9\u4e24\u4e2a\u6570\u7ec4\uff0c\u6765\u83b7\u53d6\u6700\u65b0\u7684 state \u548c\u6267\u884c\u56de\u8c03\u51fd\u6570\uff1b<\/div>\n
\u73b0\u5728\u6211\u4eec\u6765\u5b9e\u73b0 getState() \u51fd\u6570<\/div>\n
<\/div>\n
getState() {<\/div>\n
\u00a0 \u00a0 let { instance, pendingStates } = this<\/div>\n
\u00a0 \u00a0 let { state, props } = instance<\/div>\n
\u00a0 \u00a0 if (pendingStates.length > 0) {<\/div>\n
\u00a0 \u00a0 \u00a0 state = { …state }<\/div>\n
\u00a0 \u00a0 \u00a0 pendingStates.forEach(nextState => {<\/div>\n
\u00a0 \u00a0 \u00a0 \u00a0 if (_.isFn(nextState)) {<\/div>\n
\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 nextState = nextState.call(instance, state, props)<\/div>\n
\u00a0 \u00a0 \u00a0 \u00a0 }<\/div>\n
\u00a0 \u00a0 \u00a0 \u00a0 state = { …state, …nextState }<\/div>\n
\u00a0 \u00a0 \u00a0 })<\/div>\n
\u00a0 \u00a0 \u00a0 pendingStates = []<\/div>\n
\u00a0 \u00a0 }<\/div>\n
\u00a0 \u00a0 return state<\/div>\n
\u00a0 }<\/div>\n
<\/div>\n
10\u884c\u4ee3\u7801\uff0c\u5728\u6267\u884c\u66f4\u65b0\u65f6\uff0c\u901a\u8fc7getState() \u62ff\u5230\u6700\u65b0\u503c\uff0c\u901a\u8fc7\u904d\u5386pendingStates , r\u5982\u679c nextState\u662f\u51fd\u6570\u7c7b\u578b\uff0c\u5219\u76f4\u63a5\u6267\u884c\uff0c\u5e76\u4f20\u5165\u5f53\u524d\u6700\u65b0\u7684 state \u548c props\uff0c\u5982\u679c\u662f\u5bf9\u8c61\uff0c\u5219\u76f4\u63a5\u5411\u524d\u8986\u76d6\uff0c\u8fd9\u5c31\u662f\u4e3a\u4f55\u76f8\u540c\u7684key\u591a\u6b21\u6267\u884c\u5408\u5e76\u4e3a\u4e00\u6b21\u5207\u6267\u884c\u6700\u540e\u4e00\u6b21 \u7684\u539f\u56e0\uff1b<\/div>\n
<\/div>\n
\u5728\u9875\u9762\u66f4\u65b0\u5b8c\u6210\u540e\uff0c\u6267\u884c\u5b8c componentDidUpdate \uff0c\u6211\u4eec\u53bb\u8c03\u7528\u56de\u6389\u51fd\u6570\u6267\u884c<\/div>\n
<\/div>\n
clearCallbacks() {<\/div>\n
let { pendingCallbacks, instance } = this<\/div>\n
if (pendingCallbacks.length > 0) {<\/div>\n
pendingCallbacks.forEach(callback => callback.call(instance))<\/div>\n
this.pendingCallbacks = []<\/div>\n
}<\/div>\n
}<\/div>\n
<\/div>\n
\u5230\u6b64\u4e3a\u6b62\uff0c\u6211\u4eec\u518d\u56de\u8fc7\u5934\u53bb\u770b\u521a\u624d\u7684\u4e24\u4e2a\u6817\u5b50\uff0c\u662f\u4e0d\u662f\u66f4\u597d\u7406\u89e3\u4e86\u3002<\/div>\n
<\/div>\n
\n
\u6211\u4eec\u5728\u9762\u8bd5\u7684\u8fc7\u7a0b\u4e2d\u7ecf\u5e38\u4f1a\u88ab\u95ee\u5230\uff0c\u6211\u4eec\u901a\u8fc7 setState \u66f4\u6539\u72b6\u6001\u540e\u53d1\u751f\u4e86\u4ec0\u4e48\uff1f\u72b6\u6001\u662f\u5982\u4f55\u53d8\u66f4\u7684\uff1f\u672c\u671f\u5c06\u4ece\u4ee5\u4e0b\u51e0\u4e2a\u65b9\u9762\u6765\u6df1\u5165\u4e86\u89e3 setState\u7684\u5de5\u4f5c\u539f\u7406\u3002<\/div>\n
\u539f\u7406\u5256\u6790<\/div>\n
\u5b9e\u73b0\u5f02\u6b65\u961f\u5217 updateQueue\u3001Updater\u3001Component<\/div>\n
setState \u539f\u7406\u5256\u6790<\/div>\n
\u6211\u4eec\u901a\u8fc7 class Cmp extends Component \u6765\u5b9a\u4e49\u4e00\u4e2aclass \u7ec4\u4ef6\uff0c\u5728\u6e90\u7801\u4e2d\uff0cComponent\u7684\u5b9e\u73b0\u5f88\u7b80\u5355\uff0c\u9664\u4e86\u5b9a\u4e49\u4e86\u4e00\u4e9b\u5b9e\u4f8b\u53d8\u91cf\uff0c\u53ea\u6709setState \u548c forceUpdate\u4e24\u4e2a\u65b9\u6cd5\u3002<\/div>\n
<\/div>\n
class Component{<\/div>\n
static isReactComponent = {}<\/div>\n
constructor(props, context){<\/div>\n
\/\/ \u66f4\u65b0\u5668: \u7ba1\u7406\u5f53\u524d\u7ec4\u4ef6\u4e2d\u6240\u6709\u53d8\u66f4<\/div>\n
this.$updater = new Updater(this)<\/div>\n
this.$cache = { isMounted: false }<\/div>\n
this.props = props<\/div>\n
this.state = {}<\/div>\n
this.refs = {}<\/div>\n
this.context = context<\/div>\n
}<\/div>\n
\/\/ \u8df3\u8fc7\u6240\u6709\u751f\u547d\u5468\u671f\u6267\u884c\u5f3a\u5236\u66f4\u65b0\uff0c \u5b9e\u9645\u66f4\u65b0\u7ec4\u4ef6\u7684\u51fd\u6570<\/div>\n
forceUpdate(callback) {}<\/div>\n
<\/div>\n
\/\/ nextState \u53ef\u80fd\u662f\u5bf9\u8c61\u6216\u51fd\u6570<\/div>\n
setState(nextState, callback) {<\/div>\n
\/\/ \u6dfb\u52a0\u5f02\u6b65\u961f\u5217\u00a0 \u4e0d\u662f\u6bcf\u6b21\u90fd\u66f4\u65b0<\/div>\n
this.$updater.addCallback(callback)<\/div>\n
this.$updater.addState(nextState)<\/div>\n
}<\/div>\n
}<\/div>\n
<\/div>\n
\u6682\u4e14\u5148\u4e0d\u770b forceUpdate\uff0c\u5728\u7ec4\u4ef6\u4e2d\u6211\u4eec\u901a\u8fc7 new Updater(this) \u4e00\u4e2a\u66f4\u65b0\u5668\uff08\u4e0e\u7ec4\u4ef6\u4e00\u4e00\u5bf9\u5e94\uff09\uff0c\u6765\u7ba1\u7406\u7ec4\u4ef6\u7684\u6240\u6709\u53d8\u66f4\uff0csetState \u4e2d\u4e5f\u53ea\u662f\u7b80\u5355\u7684\u901a\u8fc7\u66f4\u65b0\u5668\u5c06\u53d8\u66f4\u52a8\u4f5c\u548c\u56de\u8c03\u6dfb\u52a0\u5230\u5f02\u6b65\u961f\u5217\u4e2d\u3002\u901a\u8fc7updater.addState(nextState)\u548cupdater.addCallback(callback)\u5c06 nextState \u548c callback \u5206\u522b\u6dfb\u52a0\u5230 penddingStates \u548cpeddingCallbacks\u4e2d\uff0c\u7136\u540e React \u4e2d\u901a\u8fc7 updateQueue \u6765\u7ba1\u7406\u8fd9\u4e9b updater, \u8c03\u7528 updateQueue.add \u5c06\u4efb\u52a1\u6dfb\u52a0\u5230\u961f\u5217\u7b49\u5f85\u7cfb\u7edf\u6279\u91cf\u66f4batchUpdate\u3002<\/div>\n
<\/div>\n
\u521a\u521a\u8bf4\u4e86\u4e00\u5806\uff0c\u773c\u775b\u6709\u70b9\u7f2d\u4e71\u4e86\uff0c\u6211\u4eec\u6765\u753b\u4e2a\u56fe\uff0c\u7406\u89e3\u4e00\u4e0b\u5b83\u4eec\u4e4b\u95f4\u7684\u5173\u7cfb\u3002<\/div>\n
<\/div>\n
\u75285\u5206\u949f\u7ed9\u5927\u5bb6\u7528\u56fe\u66f4\u52a0\u5ba2\u89c2\u7684\u63cf\u8ff0\u4e86 updateQueue\u3001updater\u3001Component \u7684\u5173\u7cfb\u3002<\/div>\n
\u5230\u6b64\uff0c\u6211\u4eec\u8fd8\u9700\u8981\u4e86\u89e3 updater \u662f\u5982\u4f55\u6765\u7ba1\u7406\u5f53\u524d\u7ec4\u4ef6\u53d8\u66f4\u7684\uff0c\u6765\u5b9e\u73b0\u4e00\u4e2a Updater<\/div>\n
<\/div>\n
Updater<\/div>\n
class Updater{<\/div>\n
constructor(instance){<\/div>\n
this.instance = instance \/\/ \u7ec4\u4ef6\u5b9e\u4f8b<\/div>\n
this.pendingStates = [] \/\/ \u5f85\u5904\u7406\u72b6\u6001\u6570\u7ec4<\/div>\n
this.pendingCallbacks = [] \/\/ \u5f85\u5904\u7406\u56de\u8c03\u6570\u7ec4<\/div>\n
this.isPending = false<\/div>\n
this.nextProps = this.nextContext = null<\/div>\n
this.clearCallbacks = this.clearCallbacks.bind(this)<\/div>\n
}<\/div>\n
<\/div>\n
\/\/ \u901a\u77e5\u66f4\u65b0\u51fd\u6570<\/div>\n
emitUpdate(nextProps, nextContext) {<\/div>\n
this.nextProps = nextProps<\/div>\n
this.nextContext = nextContext<\/div>\n
\/\/ \u5982\u679c\u6709\u63a5\u53d7\u5230\u65b0\u7684props\uff0c\u5219\u7acb\u5373\u66f4\u65b0<\/div>\n
nextProps || !updateQueue.isPending<\/div>\n
? this.updateComponent()<\/div>\n
: updateQueue.add(this)<\/div>\n
}<\/div>\n
<\/div>\n
\/\/ \u5b9e\u9645\u66f4\u65b0\u51fd\u6570<\/div>\n
updateComponent() {<\/div>\n
let { instance, pendingStates, nextProps, nextContext } = this<\/div>\n
if (nextProps || pendingStates.length > 0) {<\/div>\n
nextProps = nextProps || instance.props<\/div>\n
nextContext = nextContext || instance.context<\/div>\n
this.nextProps = this.nextContext = null<\/div>\n
\/\/ getState \u5408\u5e76\u6240\u6709\u7684state\u7684\u6570\u636e\uff0c\u4e00\u6b21\u66f4\u65b0<\/div>\n
shouldUpdate(instance, nextProps, this.getState(), nextContext, this.clearCallbacks)<\/div>\n
}<\/div>\n
}<\/div>\n
addState(nextState) {<\/div>\n
if (nextState) {<\/div>\n
this.pendingStates.push(nextState)<\/div>\n
\/\/ \u5982\u679c\u5f53\u524d\u961f\u5217\u7a7a\u95f2\u5219\u76f4\u63a5\u66f4\u65b0<\/div>\n
if (!this.isPending) {<\/div>\n
this.emitUpdate()<\/div>\n
}<\/div>\n
}<\/div>\n
}<\/div>\n
<\/div>\n
addCallback(callback) {<\/div>\n
if (_.isFn(callback)) {<\/div>\n
this.pendingCallbacks.push(callback)<\/div>\n
}<\/div>\n
}<\/div>\n
<\/div>\n
getState() {<\/div>\n
let { instance, pendingStates } = this<\/div>\n
let { state, props } = instance<\/div>\n
if (pendingStates.length) {<\/div>\n
state = {…state}<\/div>\n
pendingStates.forEach(nextState => {<\/div>\n
if (_.isFn(nextState)) {<\/div>\n
nextState = nextState.call(instance, state, props)<\/div>\n
}<\/div>\n
state = {…state, …nextState}<\/div>\n
})<\/div>\n
pendingStates = []<\/div>\n
}<\/div>\n
return state<\/div>\n
}<\/div>\n
<\/div>\n
clearCallbacks() {<\/div>\n
let { pendingCallbacks, instance } = this<\/div>\n
if (pendingCallbacks.length > 0) {<\/div>\n
pendingCallbacks.forEach(callback => callback.call(instance))<\/div>\n
this.pendingCallbacks = []<\/div>\n
}<\/div>\n
}<\/div>\n
}<\/div>\n
<\/div>\n
\u8fd9\u91cc Updater \u9664\u4e86\u5728 setState \u4e2d\u7528\u5230\u7684\u4e24\u4e2a\u65b9\u6cd5\uff0c\u8fd8\u5b9e\u73b0\u4e86\u53e6\u5916\u4e24\u4e2a\u91cd\u8981\u7684\u65b9\u6cd5\uff0cemitUpdate \u548c updateComponent\u5206\u522b\u7528\u4e8e\u901a\u77e5\u7ec4\u4ef6\u66f4\u65b0\u548c \u66f4\u65b0\u7ec4\u4ef6\u3002\u5728\u7ec4\u4ef6\u5b9e\u4f8b\u5316\u65f6\uff0c\u6211\u4eec\u901a\u8fc7new Updater(this)\u5c06\u7ec4\u4ef6\u5b9e\u4f8b\u5b58\u50a8\u5728 this.instance\u4e2d\u3002<\/div>\n
\u901a\u8fc7\u5206\u6790addState \u548c emitUpdate \uff0c\u7ec4\u4ef6\u53ea\u6709\u5728updater.isPedding \u548c updateQueue.isPending \u5747\u5904\u4e8e\u7a7a\u95f2\u65f6\u624d\u4f1a\u8c03\u7528 updateComponent \u53bb\u6267\u884c\u7ec4\u4ef6\u66f4\u65b0\uff0c\u6ce8\u610f\u5728 updater.isPedding \u7a7a\u95f2\u4e14\u7ec4\u4ef6\u5b58\u5728\u65b0\u7684 props \u65f6\uff0c\u7ec4\u4ef6\u4f1a\u7acb\u5373\u66f4\u65b0 \u3002<\/div>\n
<\/div>\n
OK\uff0c\u91cd\u70b9\u6765\u4e86\uff0c\u5728 updateComponent \u65b9\u6cd5\u4e2d \u7740\u91cd\u770b shouldUpdate(instance, nextProps, this.getState(), nextContext, this.clearCallbacks) \uff0c\u901a\u8fc7 this.getState() \u5c06\u5408\u5e76\u540e\u7684\u65b0\u72b6\u6001\u4f20\u5165\u65b9\u6cd5\u4e2d\uff0cthis.clearCallbacks \u662f\u7528\u6765\u6279\u91cf\u6267\u884c\u56de\u8c03\u7684\u3002<\/div>\n
<\/div>\n
\u6211\u4eec\u77e5\u9053 \u5728Component \u4e2d setState \u548c forceUpdate \u7684\u4e3b\u8981\u533a\u522b\u662f\uff0c\u524d\u8005\u4f1a\u53bb\u5224\u65ad\u662f\u5426\u9700\u8981\u6267\u884c\u66f4\u65b0\uff0c\u540e\u8005\u4f1a\u8df3\u8fc7\u8fd9\u4e9b\u6b65\u9aa4\uff0c\u5f3a\u5236\u66f4\u65b0\u3002<\/div>\n
<\/div>\n
function shouldUpdate(component, nextProps, nextState, nextContext, callback) {<\/div>\n
\/\/ \u662f\u5426\u5e94\u8be5\u66f4\u65b0 \u5224\u65adshouldComponentUpdate\u751f\u547d\u5468\u671f<\/div>\n
let shouldComponentUpdate = true<\/div>\n
if (component.shouldComponentUpdate) {<\/div>\n
shouldComponentUpdate = component.shouldComponentUpdate(nextProps, nextState, nextContext)<\/div>\n
}<\/div>\n
if (shouldComponentUpdate === false) {<\/div>\n
component.props = nextProps<\/div>\n
component.state = nextState<\/div>\n
component.context = nextContext || {}<\/div>\n
return<\/div>\n
}<\/div>\n
let cache = component.$cache<\/div>\n
cache.props = nextProps<\/div>\n
cache.state = nextState<\/div>\n
cache.context = nextContext || {}<\/div>\n
component.forceUpdate(callback)<\/div>\n
}<\/div>\n
<\/div>\n
\u53ef\u4ee5\u770b\u51fa\uff0c\u7ed5\u4e86\u8fd9\u4e48\u591a\uff0c\u771f\u6b63\u6267\u884c\u66f4\u65b0\u7684\u662f\u7ec4\u4ef6\u5b9e\u4f8b\u7684 forceUpdate, \u5728\u6267\u884c\u66f4\u65b0\u524d\uff0c\u56de\u53bb\u5224\u65ad\u7ec4\u4ef6\u662f\u5426\u6709\u5b9a\u4e49 shouldComponentUpdate \uff0c\u6839\u636e\u5176\u8fd4\u56de\u503c\u6765\u51b3\u5b9a\u662f\u5426\u66f4\u65b0\uff0c\u5c06\u5f53\u524d\u72b6\u6001\u548c\u53c2\u6570\u7f13\u5b58\u5728$cache\u4e2d\uff0c\u663e\u7136\u5728 forceUpdate \u4e2d\u6211\u4eec\u4f1a\u7528\u5230\u3002<\/div>\n
<\/div>\n
foreUpdate<\/div>\n
forceUpdate \u4f1a\u8df3\u8fc7\u6240\u6709\u751f\u547d\u5468\u671f\uff0c\u5f3a\u5236\u6267\u884c\u7ec4\u4ef6\u66f4\u65b0\u3002<\/div>\n
<\/div>\n
forceUpdate(callback) {<\/div>\n
let { $updater, $cache, props, state, context } = this<\/div>\n
if (!$cache.isMounted) {<\/div>\n
return<\/div>\n
}<\/div>\n
if ($updater.isPending) {<\/div>\n
\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 $updater.addState(state)<\/div>\n
return;<\/div>\n
}<\/div>\n
let nextProps = $cache.props || props<\/div>\n
let nextState = $cache.state || state<\/div>\n
let nextContext = $cache.context || context<\/div>\n
let parentContext = $cache.parentContext<\/div>\n
let node = $cache.node<\/div>\n
let vnode = $cache.vnode<\/div>\n
$cache.props = $cache.state = $cache.context = null<\/div>\n
$updater.isPending = true<\/div>\n
if (this.componentWillUpdate) {<\/div>\n
this.componentWillUpdate(nextProps, nextState, nextContext)<\/div>\n
}<\/div>\n
this.state = nextState<\/div>\n
this.props = nextProps<\/div>\n
this.context = nextContext<\/div>\n
<\/div>\n
\/\/ \u5bf9\u6bd4vnode<\/div>\n
\u00a0 \u00a0 let newVnode = renderComponent(this)<\/div>\n
let newNode = compareTwoVnodes(vnode, newVnode, node, getChildContext(this, parentContext))<\/div>\n
if (newNode !== node) {<\/div>\n
newNode.cache = newNode.cache || {}<\/div>\n
syncCache(newNode.cache, node.cache, newNode)<\/div>\n
}<\/div>\n
$cache.vnode = newVnode<\/div>\n
$cache.node = newNode<\/div>\n
clearPending()<\/div>\n
if (this.componentDidUpdate) {<\/div>\n
this.componentDidUpdate(props, state, context)<\/div>\n
}<\/div>\n
if (callback) {<\/div>\n
callback.call(this)<\/div>\n
}<\/div>\n
$updater.isPending = false<\/div>\n
$updater.emitUpdate()<\/div>\n
}<\/div>\n
<\/div>\n
\u53ef\u4ee5\u6682\u65f6\u4e0d\u770b\u7f13\u5b58\u548c\u865a\u62df dom \u76f8\u5173\u65b9\u6cd5\u7684\u5177\u4f53\u5b9e\u73b0\u90e8\u5206\uff0c\u5728forceUpdate\u4e2d\uff0c\u6267\u884c\u8fc7\u7a0b\u662f\uff1a<\/div>\n
isPending = true \u2014\u2014> \u6267\u884c componentWillUpdate \u2014\u2014> \u5bf9\u6bd4vnode\uff0c\u66f4\u65b0 dom \u2014\u2014> \u6267\u884ccomponentDidUpdate \u2014\u2014> \u6279\u91cf\u6267\u884c\u56de\u8c03 \u2014\u2014> isPending = false \u2014\u2014> \u7ee7\u7eed\u8c03\u7528emitUpdate \u76f4\u5230\u6ca1\u6709\u9700\u8981\u66f4\u65b0\u5de5\u4f5c\uff08!(nextProps || pendingStates.length > 0)\uff09\u3002<\/div>\n
<\/div>\n
\u6700\u540e\uff0c\u8865\u9f50\u4e0b updateQueue \u76f8\u5173\u7684\u5b9e\u73b0\u3002<\/div>\n
<\/div>\n
updateQueue<\/div>\n
let updateQueue = {<\/div>\n
updaters: [],<\/div>\n
isPending: false,<\/div>\n
add(updater) {<\/div>\n
this.updaters.push(updater)<\/div>\n
},<\/div>\n
batchUpdate() {<\/div>\n
if (this.isPending) {<\/div>\n
return<\/div>\n
}<\/div>\n
this.isPending = true<\/div>\n
let { updaters } = this<\/div>\n
let updater<\/div>\n
while (updater = updaters.pop()) {<\/div>\n
updater.updateComponent()<\/div>\n
}<\/div>\n
this.isPending = false<\/div>\n
}<\/div>\n
}<\/div>\n
<\/div>\n
\u603b\u7ed3<\/div>\n
\u8bf4\u4e86\u8fd9\u4e48\u591a\uff0c\u6700\u540e\u6211\u4eec\u6765\u7406\u4e00\u4e0b\u601d\u8def\uff0c\u518d\u6765\u753b\u4e00\u5f20\u56fe\uff0c\u6e90\u4ee3\u7801\u540e\u671f\u6574\u7406\u540e\u4f1a\u653e\u5728github\u4e2d\u3002<\/div>\n
<\/div>\n
\u7531\u6b64\u53ef\u89c1\uff0csetState \u5728\u5408\u6210\u4e8b\u4ef6\u548c\u52fe\u5b50\u51fd\u6570\u4e2d\u4e4b\u6240\u4ee5\u662f\u5f02\u6b65\u7684\uff0c\u662f\u56e0\u4e3a\u6267\u884c\u51fd\u6570\u5728\u66f4\u65b0\u52a8\u4f5c\u524d\u5c31\u6267\u884c\u4e86\u3002<\/div>\n
<\/div>\n
<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

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