刚学redux, 不是很明白一下两个function的参数state和dispatch是从哪里来的?求明白人给讲讲!!!
function mapStateToProps(state){
return {
counter: state.counter
}
}
function mapDispatchToProps(dispatch){
return bindActionCreators(actions, dispatch)
}
connect 传过来的
mapStateToProps(state)中的初始state, 可以在创建store的时候指定一个initialState, 代码:
const initialState = Immutable.fromJS(
{
visibilityFilter: "SHOW_ALL",
todos:[
{completed: false, text: "12332"},
{completed: false, text: "321"},
{completed: true, text: "def"},
{completed: false, text: "abc"}
]
}
);
let createStoreWithMiddleware = redux.applyMiddleware(loggerMiddleware)(redux.createStore);
const store = createStoreWithMiddleware(reducers, initialState);
也可以不指定initialState. redux的container组件在执行connect()方法的时候, 会默认调用一个type="@@redux/INIT"的action, 这样的话可以直接在reducer中处理初始state为空的情况, 代码:
function todos(state=initialState.get("todos"), action={}){
switch (action.type){
case ADD_TODO:
const tmp = state.push(Immutable.Map({text:action.text, completed:false}));
return tmp;
case COMPLETE_TODO:
return state.setIn([action.index, "completed"], true);
default :
return state
}
}
const reducers = {
visibilityFilter,
todos
};
module.exports = combineReducers(reducers);
注意: 在使用第一种方法传入initialState时, 如果使用的是Immutable, 默认情况下会报错:The initialState argument passed to createStore has unexpected type of "Object". 修改的办法是安装redux-immutable, 使用redux-immutable创建reducer, 代码:
import {
combineReducers
} from 'redux-immutable';
const reducers = {
visibilityFilter,
todos
};
module.exports = combineReducers(reducers);
木有人回答。。。