Question

我正在使用Redux在此项目/示例中实现基本的Like计数器

https://codesandbox.io/s/github/mralwin/Reduxstagram

以下是用于管理点赞状态增加的以下代码：

操作

export function increment(index) {
  return {
    type: "INCREMENT_LIKES",
    index
  };
}

减速器

function posts(state = [], action) {
  switch (action.type) {
    case "INCREMENT_LIKES":
      const i = action.index;
      return [
        ...state.slice(0, i), // before the one we are updating
        { ...state[i], likes: state[i].likes + 1 },
        ...state.slice(i + 1) // after the one we are updating
      ];
    default:
      return state;
  }
}

组件

<button onClick={this.props.increment.bind(null, i)} className="likes">

现在，我想在练习中添加一个减小功能来管理减小状态之类的，这里是问题的出处。

查看代码：

操作

export function decrease(index) {
  return {
    type: 'DECREASE_LIKES',
    index: i
  };
}

减速器 =>添加了 DECREASE_LIKES 案例

function rooms(state = [], action) {
  switch (action.type) {
    case 'INCREMENT_LIKES' :
      const i = action.index;
      return [
        ...state.slice(0, i),
        {...state[i], likes: state[i].likes + 1 },
        ...state.slice(i + 1)
      ];
    case 'DECREASE_LIKES' :
      return [
        ...state.slice(0, i),
        {...state[i], likes: state[i].likes - 1 },
        ...state.slice(i + 1)
      ];
    default:
      return state;
  }
}

组件

<button onClick={this.props.decrease.bind(null, i)} className="likes">

虽然我正在调试，但在减小情况下，状态是不确定的。

我在做什么错？我该如何解决？

Answer 1

在reducers switch语句的i情况下，似乎未定义变量DECREASE_LIKES。因此，这将导致DECREASE_LIKES减少的逻辑产生错误的结果。

请考虑对减速器进行以下调整以解决该问题：

function rooms(state = [], action) {
  switch (action.type) {
    case 'INCREMENT_LIKES' : {
      const i = action.index;
      return [
        ...state.slice(0, i),
        {...state[i], likes: state[i].likes + 1 },
        ...state.slice(i + 1)
      ];
    }
    case 'DECREASE_LIKES' : {
      // Use a different variable for visual distinction/clarity
      const j = action.index;

      // Use j from action index in reduction logic for this action
      return [
        ...state.slice(0, j),
        {...state[j], likes: state[j].likes - 1 },
        ...state.slice(j + 1)
      ];
    }
    default:
      return state;
  }
}

React：减少动作导致Redux Reducer中的状态不确定

1 个答案: