我该如何在React中强制使用钩子重新渲染组件?

问题描述

考虑以下钩子示例

   import { useState } from 'react';

   function Example() {
       const [count, setCount] = useState(0);

       return (
           <div>
               <p>You clicked {count} times</p>
               <button onClick={() => setCount(count + 1)}>
                  Click me
               </button>
          </div>
        );
     }

基本上，我们使用this.forceUpdate()方法强制组件在React类组件中立即重新呈现，如下面的示例

Basically we use this.forceUpdate() method to force the component to re-render immediately in React class components like below example

    class Test extends Component{
        constructor(props){
             super(props);
             this.state = {
                 count:0,
                 count2: 100
             }
             this.setCount = this.setCount.bind(this);//how can I do this with hooks in functional component
        }
        setCount(){
              let count = this.state.count;
                   count = count+1;
              let count2 = this.state.count2;
                   count2 = count2+1;
              this.setState({count});
              this.forceUpdate();
              //before below setState the component will re-render immediately when this.forceUpdate() is called
              this.setState({count2: count
        }

        render(){
              return (<div>
                   <span>Count: {this.state.count}></span>.
                   <button onClick={this.setCount}></button>
                 </div>
        }
 }

但是我的查询是如何强制上述功能组件立即通过钩子重新渲染?

But my query is How can I force above functional component to re-render immediately with hooks?

推荐答案

由于 useState在内部使用useReducer :

This is possible with useState or useReducer, since useState uses useReducer internally:

const [, updateState] = React.useState();
const forceUpdate = React.useCallback(() => updateState({}), []);

forceUpdate不能在正常情况下使用，仅在测试或其他突出情况下使用.这种情况可能会以更常规的方式解决.

forceUpdate isn't intended to be used under normal circumstances, only in testing or other outstanding cases. This situation may be addressed in a more conventional way.

setCount是未正确使用forceUpdate的示例，出于性能原因，setState是异步的，不应仅因为状态更新未正确执行而被迫同步.如果状态依赖于先前设置的状态，则应使用更新程序功能来完成，

setCount is an example of improperly used forceUpdate, setState is asynchronous for performance reasons and shouldn't be forced to be synchronous just because state updates weren't performed correctly. If a state relies on previously set state, this should be done with updater function,

< ...>

<...>

由updater函数接收的状态和道具均得到保证是最新的.更新程序的输出与状态.

Both state and props received by the updater function are guaranteedto be up-to-date. The output of the updater is shallowly merged withstate.

setCount可能不是说明性的示例，因为其用途尚不清楚，但更新程序功能就是这种情况:

setCount may not be an illustrative example because its purpose is unclear but this is the case for updater function:

setCount(){
  this.setState(({count}) => ({ count: count + 1 }));
  this.setState(({count2}) => ({ count2: count + 1 }));
  this.setState(({count}) => ({ count2: count + 1 }));
}

这将1:1转换为钩子，但最好将用作回调的函数记住:

This is translated 1:1 to hooks, with the exception that functions that are used as callbacks should better be memoized:

   const [state, setState] = useState({ count: 0, count2: 100 });

   const setCount = useCallback(() => {
     setState(({count}) => ({ count: count + 1 }));
     setState(({count2}) => ({ count2: count + 1 }));
     setState(({count}) => ({ count2: count + 1 }));
   }, []);

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