reducer 函数如何知道 count 是状态项？

Question

我不明白 reducer 如何在代码中不使用状态名称的情况下知道计数来自状态。我认为它就像“return {state.count: state.count + 1}”。它是如何工作的？

import { useReducer } from 'react';
    
    const initialState = {count: 0};
    
    const reducer = (state, action) =>{
      switch(action.type){
        case 'minus':
          return {count: state.count + 1}
        break;
        case 'plus':
          return {count: state.count - 1}
        break;
        case 'reset':
          return initialState;
        break;
      }
      return state;
    }
    
    const App = () =>{
      const [state, dispatch] = useReducer(reducer, initialState);
    
      return(
        <div>
          <button onClick={() => dispatch({type: 'menos'})}>-</button>
          <div>{state.count}</div>
          <button onClick={() => dispatch({type: 'mais'})}>+</button>
          <button onClick={() => dispatch({type: 'reset'})}>reset</button>
        </div>
      );
    }
    
    export default App;

Answer 1

您已经声明了 reducer 函数和操作。您的调度查看您的操作类型并更改状态 accordingly.you 不需要提供状态名称只需要提供操作类型。

reducer 函数如何知道 count 是状态项？

How does the reducer function know that count is a state's item?

javascript

reactjs