zoukankan      html  css  js  c++  java
  • [Redux] Colocating Selectors with Reducers

    We will learn how to encapsulate the knowledge about the state shape in the reducer files, so that the components don’t have to rely on it.

    In current VisibleTodoList.js:

    import { connect } from 'react-redux';
    import { withRouter } from 'react-router';
    import { toggleTodo } from '../actions';
    import TodoList from './TodoList';
    
    const getVisibleTodos = (todos, filter) => {
      switch (filter) {
        case 'all':
          return todos;
        case 'completed':
          return todos.filter(t => t.completed);
        case 'active':
          return todos.filter(t => !t.completed);
        default:
          throw new Error(`Unknown filter: ${filter}.`);
      }
    };
    
    const mapStateToProps = (state, { params }) => ({
      todos: getVisibleTodos(state.todos, params.filter || 'all'),
    });
    
    const VisibleTodoList = withRouter(connect(
      mapStateToProps,
      { onTodoClick: toggleTodo }
    )(TodoList));
    
    export default VisibleTodoList;

    Currently, the getVisibleTodos(state.todos), depends on state's structure.

    Move getVisibleTodos to reducer file:

    const todo = (state, action) => {
      switch (action.type) {
        case 'ADD_TODO':
          return {
            id: action.id,
            text: action.text,
            completed: false,
          };
        case 'TOGGLE_TODO':
          if (state.id !== action.id) {
            return state;
          }
          return {
            ...state,
            completed: !state.completed,
          };
        default:
          return state;
      }
    };
    
    const todos = (state = [{
      id: 0,
      text: "ok",
      completed: false
    }], action) => {
      switch (action.type) {
        case 'ADD_TODO':
          return [
            ...state,
            todo(undefined, action),
          ];
        case 'TOGGLE_TODO':
          return state.map(t =>
            todo(t, action)
          );
        default:
          return state;
      }
    };
    
    export default todos;
    
    
    export const getVisibleTodos = (state, filter) => {
      switch (filter) {
        case 'all':
          return state;
        case 'completed':
          return state.filter(t => t.completed);
        case 'active':
          return state.filter(t => !t.completed);
        default:
          throw new Error(`Unknown filter: ${filter}.`);
      }
    };

    Then in the RootReducer, we manage the state:

    import { combineReducers } from 'redux';
    import todos, * as fromTodos from './todos';
    
    const todoApp = combineReducers({
      todos
    });
    
    export default todoApp;
    
    export const getVisibleTodos = (state, filter) =>
        fromTodos.getVisibleTodos(state.todos, filter);

    Use it in VisibleTodoList.js:

    import {connect} from 'react-redux';
    import {toggleTodo} from '../actions';
    import TodoList from './TodoList';
    import {withRouter} from 'react-router';
    import { getVisibleTodos } from '../reducers';
    
    
    const mapStateToProps = (state, {params}) => {
        return {
            todos: getVisibleTodos(state, params.filter || 'all'), // if filter is '' then change to 'all'
        };
    };
    
    const VisibleTodoList = withRouter(connect(
        mapStateToProps,
        {onTodoClick: toggleTodo}
    )(TodoList));
    
    export default VisibleTodoList;
  • 相关阅读:
    Java内存泄漏分析系列之七:使用MAT的Histogram和Dominator Tree定位溢出源
    Java内存泄漏分析系列之六:JVM Heap Dump(堆转储文件)的生成和MAT的使用
    Java内存泄漏分析系列之五:常见的Thread Dump日志案例分析
    Java内存泄漏分析系列之四:jstack生成的Thread Dump日志线程状态
    Java内存泄漏分析系列之三:jstat命令的使用及VM Thread分析
    Java内存泄漏分析系列之二:jstack生成的Thread Dump日志结构解析
    Java内存泄漏分析系列之一:使用jstack定位线程堆栈信息
    安全框架Shiro
    JDK动态代理与CGLib动态代理
    解读分库分表中间件Sharding-JDBC
  • 原文地址:https://www.cnblogs.com/Answer1215/p/5565084.html
Copyright © 2011-2022 走看看