如何将值插入到嵌套Swift Dictionary中 [英] How to insert values into a nested Swift Dictionary

问题描述

我正在尝试在字典中插入新的键值对，嵌套在另一个字典中：

< pre $ var dict = Dictionary< Int，Dictionary< Int，String>>（）

dict.updateValue（[1：one，2：两个]，forKey：1）
dict [1]？[1] // {Someone}

如果var insideDic = dict [1] {
/ /这是一个副本，所以我不能这样插入：
insideDic [3] =three
}

dict //仍然[1：[1 ：one，2：two]]

dict [1]？[3] =three//无法分配给这个表达式的结果
dict [1] ？.updateValue（three，forKey：3）//找不到成员updateValue


我认为应该是一个简单的方法来处理它，但我花了一个小时，仍然无法弄清楚。
我可以使用 NSDictionary ，但我真的很想了解如何在Swift中管理嵌套的字典 ？

解决方案

词典是值类型，因此在作业上复制。因此，您将得到内部字典（将是副本），添加新密钥，然后重新分配。

  //获取嵌套字典（将是副本）
 var inner：Dictionary< Int，String> = dict [1]！ 
 
 //添加新值
 inner [3] =three
 
 //更新外部字典
 dict [1] =内
 println（dict）// [1：[1：one，2：two，3：three]] 
  

您可以使用其中一个新的实用程序库，例如 ExSwift ，使其有一点简单：

  dict [1] = dict [1] !. union（[3：three]）
  

这使用 union方法，它结合了两个字典。

I'm trying to insert new key-value pair in dictionary, which nested in another one Dictionary:

var dict = Dictionary<Int, Dictionary<Int, String>>()

dict.updateValue([1 : "one", 2: "two"], forKey: 1)
dict[1]?[1] // {Some "one"}

if var insideDic =  dict[1] {
    // it is a copy, so I can't insert pair this way:
    insideDic[3] = "three"
}

dict // still [1: [1: "one", 2: "two"]]

dict[1]?[3] = "three" // Cannot assign to the result of this expression
dict[1]?.updateValue("three", forKey: 3) // Could not find a member "updateValue"

I believe should be a simple way to handle it, but I spent an hour and still can't figure it out. I can use NSDictionary instead, but I really like to understand how I should manage nested Dictionaries in Swift?

解决方案

Dictionarys are value types so are copied on assignment. As a result you are going to have to get the inner dictionary (which will be a copy), add the new key, then re-assign.

// get the nested dictionary (which will be a copy)
var inner:Dictionary<Int, String> = dict[1]!

// add the new value
inner[3] = "three"

// update the outer dictionary
dict[1] = inner
println(dict) // [1: [1: one, 2: two, 3: three]]

You could use one of the new utility libraries such as ExSwift to make this a bit simpler:

dict[1] = dict[1]!.union([3:"three"])

This uses the union method that combines two dictionaries.

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