Swift 3：数组到词典？ [英] Swift 3: Array to Dictionary?

问题描述

我有一个大型数组，需要通过一个键（查找）来访问它，所以我需要创建Dictionary。有没有一个内置的函数在Swift 3.0中这样做，还是我需要自己写？

首先，我将需要它为一个类与键字符串后来也许我可以为通用目的（所有类型的数据和键）编写一个模板版本。 解决方案

我想你正在寻找这样的东西：

$ p $ {
public func toDictionary< Key：Hashable> （使用selectKey：（Element） - > Key） - > [Key：Element] {
var dict = [Key：Element]（）
for self {
dict [selectKey（element）] = element
}





$ b现在你可以这样做：

  struct Person {
 var name：String 
 var surname：String 
 var identifier：String $ b （姓名：John，姓：Doe，标识符：JOD），
个人（姓名：Jane，姓： （dict）//结果：[JAD：Person（name） ：Jane，姓：Doe，标识符：JAD），JOD：人（姓名：John，姓：Doe，标识符：JOD）] 
  
 
 
 
 
如果你希望你的代码更一般，你甚至可以添加这个序列而不是 Array ：
 扩展序列{
 pub lic func toDictionary< Key：Hashable>（with selectKey：（Iterator.Element） - > Key） - > [Key：Iterator.Element] {
 var dict：[Key：Iterator.Element] = [：] 
 for self {
 dict [selectKey（element）] = element 
 
 return dict 
 
 
 code 
 
 
 
 ，这会导致序列迭代，在某些情况下可能有副作用。
 
I have a large array and need to access it by a key (a lookup) so I need to create Dictionary.  Is there a built in function in Swift 3.0 to do so, or do I need to write it myself?

First I will need it for a class with key "String" and later on maybe I will be able to write a template version for general purpose (all types of data and key).
解决方案
I think you're looking for something like this:
extension Array {
    public func toDictionary<Key: Hashable>(with selectKey: (Element) -> Key) -> [Key:Element] {
        var dict = [Key:Element]()
        for element in self {
            dict[selectKey(element)] = element
        }
        return dict
    }
}
You can now do:
struct Person {
    var name: String
    var surname: String
    var identifier: String
}

let arr = [Person(name: "John", surname: "Doe", identifier: "JOD"),
           Person(name: "Jane", surname: "Doe", identifier: "JAD")]
let dict = arr.toDictionary { $0.identifier }

print(dict) // Result: ["JAD": Person(name: "Jane", surname: "Doe", identifier: "JAD"), "JOD": Person(name: "John", surname: "Doe", identifier: "JOD")]




If you'd like your code to be more general, you could even add this extension on Sequence instead of Array:
extension Sequence {
    public func toDictionary<Key: Hashable>(with selectKey: (Iterator.Element) -> Key) -> [Key:Iterator.Element] {
        var dict: [Key:Iterator.Element] = [:]
        for element in self {
            dict[selectKey(element)] = element
        }
        return dict
    }
}
Do note, that this causes the Sequence to be iterated over and could have side effects in some cases.

                        
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