如何复制地图？ [英] How to copy a map?

问题描述

我试图将另一个（ aSuperMap ）中的地图内容（ amap ）和然后清除 amap ，以便它可以在下一次迭代/循环中获取新值。
问题在于，您无法在supermap中清除地图而不清除其参考。
这里是一些伪代码。

I'm trying to copy the contents of a map ( amap ) inside another one (aSuperMap) and then clear amap so that it can take new values on the next iteration/loop. The issue is that you can't clear the map without to clear its reference in the supermap as well. Here is some pseudo code.

for something := range fruits{
        aMap := make(map[string]aStruct)
        aSuperMap := make(map[string]map[string]aStruct)

        for x := range something{
            aMap[x] = aData
            aSuperMap[y] = aMap
            delete(aMap, x)
    }
//save aSuperMap
  saveASuperMap(something)

}

我也尝试了一些动态的东西，但显然它会抛出一个错误（不能赋给nil） / p>

I've also tried some dynamic stuff but obviously it throws an error (cannot assign to nil)

aSuperMap[y][x] = aData

问题是我该如何创建一个关联映射？在PHP中，我只需使用aSuperMap [y] [x] = aData。看来，golang没有任何明显的方法。如果我删除 delete（aMap，x），则超级地图的引用也会被删除。如果我不删除它，supermap会以重复数据结束。基本上在每个循环中，它都会得到 aMap ，新值加上所有旧值。

The question is how can I create an associative map ? In PHP I simply use aSuperMap[y][x] = aData. It seems that golang doesn't have any obvious method. If I delete delete(aMap, x) its reference from the super map is deleted as well. If I don't delete it the supermap ends up with duplicate data. Basically on each loop it gets aMap with the new value plus all the old values.

推荐答案

您不复制地图，而是复制地图。因此， delete 会修改原始地图和超级地图中的值。要复制地图，您必须使用作为循环，如下所示：

You are not copying the map, but the reference to the map. Your delete thus modifies the values in both your original map and the super map. To copy a map, you have to use a for loop like this:

for k,v := range originalMap {
  newMap[k] = v
}

下面是一个来自现在退役的SO文档的例子：

Here's an example from the now-retired SO documentation:

// Create the original map
originalMap := make(map[string]int)
originalMap["one"] = 1
originalMap["two"] = 2

// Create the target map
targetMap := make(map[string]int)

// Copy from the original map to the target map
for key, value := range originalMap {
  targetMap[key] = value
}

a href =https://web.archive.org/web/20171006194258/https://stackoverflow.com/documentation/go/732/maps/9834/copy-a-map#t=20171006194258443316 =noreferrer >地图 - 复制地图。原作者是 JepZ 。可以在撰稿人页面上找到归因详情。该源根据 CC BY-SA 3.0 进行许可，可以在文档档案。参考主题ID：732和示例ID：9834。

Excerpted from Maps - Copy a Map. The original author was JepZ. Attribution details can be found on the contributor page. The source is licenced under CC BY-SA 3.0 and may be found in the Documentation archive. Reference topic ID: 732 and example ID: 9834.

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