Question

我正在使用简单的年龄递增和递减示例来学习redux，这里的代码是

const { createStore } = require(`redux`);


const initialState = {age: 21};

const reducerOne = (state = initialState, action) => {
    const newState = {...state};
    if(action.type === `ADD`) {
        newState.age = action.value;
    }
    if(action.type === `SUBTRACT`) {
        newState.age = action.value;
    }
    return newState;
}

const store = createStore(reducerOne);

store.subscribe(() => {
    console.log(`State Changed` + JSON.stringify(store.getState()));
})

store.dispatch({type: `ADD`, val: 10});
store.dispatch({type: `SUBTRACT`, val: 5});

但是在Output中，它显示如下-> State Changed {} 帮助解决此问题并获取输出

Answer 1

您的操作正在发布val属性，而减速器正在读取value属性。

以这种方式更改操作，它将起作用：

store.dispatch({type: `ADD`, value: 10});
store.dispatch({type: `SUBTRACT`, value: 5});

编辑：

您要替换旧的age值，但是可能要添加或减去它。您必须修改减速器才能实现这种行为：

const reducerOne = (state = initialState, action) => {
    const newState = {...state};
    if(action.type === `ADD`) {
        // add to the previous `age` value and do not overwrite it
        newState.age = state.age + action.value;
    }

    if(action.type === `SUBTRACT`) {
        // subtract from the previous `age` value and do not overwrite it
        newState.age = state.age - action.value;
    }
    return newState;
}

为什么在redux中输出会这样->状态已更改{}

1 个答案: