如何使用不变性助手更新数组中的嵌套对象? [英] how to use Immutability helper to update a nested object within an array?

问题描述

在reducer内部，给定一个状态对象:

Inside reducer, given a state object:

var state = {
        "data": [{
            "subset": [{
                "id": 1
            }, {
                "id": 2
            }]
        }, {
            "subset": [{
                "id": 10
            }, {
                "id": 11
            }, {
                "id": 12
            }]
        }]
    }

如您所见，数据是一个嵌套数组，其每个元素中都有数组.

As you can see, the data is a nested array, with arrays in each of its elements.

知道 action.indexToUpdate 将是数据的索引，我想以编程方式将 data[action.indexToUpdate].subset 更新为新数组.例如，如果 action.indexToUpdate = 0，则 data[0] 将从

Knowning that action.indexToUpdate will be a index for data, I want to update data[action.indexToUpdate].subset to a new array programmatically. For example, if action.indexToUpdate = 0, then data[0] will be updated from

[{"id":1},{"id":2}]

到

[{"id":4},{"id":5}]

为了做到这一点，我有:

In order to do so, I have:

let newSubset = [{"id":4},{"id":5}]
let newState = update(state.data[action.indexToUpdate], {
                subset: {
                    newSubset,
                },
            })

但是当我执行这个时，它返回错误:

But when I executed this, it returns error:

TypeError: value is undefined

关于更新功能.

我一直在查看这里的 react ducommentation:https://facebook.github.io/react/docs/update.html 但我真的不知道该怎么做.请指教！

I have been looking at the react ducomentation here: https://facebook.github.io/react/docs/update.html but I couldn't really figure out how to do it. Please advise!

推荐答案

你的更新看起来像

 var obj = {"state" : {
    "data": [{
        "subset": [{
            "id": 1
        }, {
            "id": 2
        }]
    }, {
        "subset": [{
            "id": 10
        }, {
            "id": 11
        }, {
            "id": 12
        }]
    }]
}}
return update(obj, {
  "state" : {
      "data": {
          [action.indexToUpdate]: {
            "subset": {
                 $set: [newSubset]
            }
          }
      }
  }
})

如果子集中有其他字段，但您只想更改包含其他键的特定索引处的字段，您可以编写

In case there are other fields in subset, but you only wish to the change the fields at specific index containing other keys, you would write

return update(obj, {
  "state" : {
      "data": {
          [action.indexToUpdate]: {
            "subset": {
                [id]: {$merge: newSubset}
            }
          }
      }
  }
})

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