如何从Swift的Dictionary中的特定索引获取密钥？ [英] How do I get the key at a specific index from a Dictionary in Swift?

问题描述

我在Swift中有一个字典，我想在特定索引中获取密钥。

I have a Dictionary in Swift and I would like to get a key at a specific index.

var myDict : Dictionary<String,MyClass> = Dictionary<String,MyClass>()

我知道我可以迭代键并记录它们

I know that I can iterate over the keys and log them

for key in myDict.keys{

    NSLog("key = \(key)")

}

然而，奇怪的是，这样的东西是不可能的

However, strangely enough, something like this is not possible

var key : String = myDict.keys[0]

为什么？

推荐答案

这是因为键返回 LazyMapCollection& [Key：Value]，Key> ，不能用Int进行下标。一种处理这种情况的方法是通过您要下标的整数来推进字典的 startIndex ，例如：

That's because keys returns LazyMapCollection<[Key : Value], Key>, which is can't be subscripted with an Int. One way to handle this is to advance the dictionary's startIndex, by the integer that you wanted to subscript by, for example:

let intIndex = 1 // where intIndex < myDictionary.count
let index = myDictionary.startIndex.advancedBy(intIndex) // index 1
myDictionary.keys[index]

另一种可能的解决方案是将键作为输入初始化一个数组，然后可以对结果使用整数下标： / p>

Another possible solution, would be to initialize an array with keys as input, then you can use integer subscripts on the result:

let firstKey = Array(myDictionary.keys)[0] // or .first

请记住，字典本来是无序的，所以不要指望给定索引的键总是一样的。

Remember, dictionaries are inherently unordered, so don't expect the key at a given index to always be the same.

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