[英]Changing a nested array value based on a given index in a reducer while not mutating state
I have a reducer working with an object with arrays.我有一个减速器处理一个带有数组的对象。 I want to change a value on the nested arrays based on a given index.
我想根据给定的索引更改嵌套数组上的值。 This code works but I can't seem to get my test to work using deep freeze.
此代码有效,但我似乎无法使用深度冻结使我的测试正常工作。 I was trying to look at the redux example here http://redux.js.org/docs/basics/Reducers.html using
.map
to find the index with no luck.我试图在这里查看 redux 示例http://redux.js.org/docs/basics/Reducers.html使用
.map
来查找索引但没有运气。 Any ideas?有任何想法吗?
export default function myReducer(state = { toDisplay: [] }, action) {
const { type, groupIndex, itemIndex } = action;
const newObject = Object.assign({}, state);
switch (type) {
case actionTypes.TOGGLE_GROUP:
newObject.toDisplay[groupIndex].isSelected = newObject.toDisplay[groupIndex].isSelected ? false : 'selected';
return newObject;
case actionTypes.TOGGLE_ITEM:
newObject.toDisplay[groupIndex].values[itemIndex].isSelected = newObject.toDisplay[groupIndex].values[itemIndex].isSelected ? false : true;
return newObject;
default:
return state;
}
}
EDIT:编辑:
For anyone curious after watching a helpful redux video I came up with this:对于观看有用的redux 视频后好奇的人,我想出了这个:
export default function myReducer(state = { toDisplay: [] }, action) {
const { type, groupIndex, itemIndex } = action;
switch (type) {
case actionTypes.TOGGLE_GROUP:
return {
...state,
toDisplay: [
...state.toDisplay.slice(0, groupIndex),
{
...state.toDisplay[groupIndex],
isSelected: state.toDisplay[groupIndex].isSelected ? false : 'selected'
},
...state.toDisplay.slice(groupIndex + 1)
]
};
case actionTypes.TOGGLE_ITEM:
return {
...state,
toDisplay: [
...state.toDisplay.slice(0, groupIndex),
{
...state.toDisplay[groupIndex],
values: [
...state.toDisplay[groupIndex].values.slice(0, itemIndex),
{
...state.toDisplay[groupIndex].values[itemIndex],
isSelected: state.toDisplay[groupIndex].values[itemIndex].isSelected ? false : true
},
...state.toDisplay[groupIndex].values.slice(itemIndex + 1)
]
},
...state.toDisplay.slice(groupIndex + 1)
]
};
default:
return state;
}
}
Using a helper/library like suggested is probably the best route but my team wishes to not add another dependency.使用建议的助手/库可能是最好的方法,但我的团队不希望添加其他依赖项。
Firstly, Object.assign(...)
only does a shallow copy.首先,
Object.assign(...)
只做一个浅拷贝。 See here .见这里。
As you have objects nested inside arrays nested inside objects I would highly recommend the immutability helpers from react (as mentioned by Rafael).由于您将对象嵌套在嵌套在对象内部的数组中,我强烈推荐 react 中的不变性助手(如 Rafael 所述)。 These allow you to do something like this:
这些允许你做这样的事情:
case actionTypes.TOGGLE_GROUP:
return update(state, {
toDisplay: {
[groupIndex]: {
isSelected: {$set: newObject.toDisplay[groupIndex].isSelected ? false : 'selected'}
}
}
});
If you are looking to modify a simple value inside an array with raw js then you can use something like this:如果您想使用原始 js 修改数组中的简单值,那么您可以使用以下内容:
return list
.slice(0,index)
.concat([list[index] + 1])
.concat(list.slice(index + 1));
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