Swift等同于`[NSDictionary initWithObjects：forKeys：]` [英] Swift equivalent to `[NSDictionary initWithObjects: forKeys:]`

问题描述

说我有两个数组，包含键和值，并希望将它们放在一个字典中。在Objective-C中，我会这样做：

  NSArray * keys = @ [@one，@two ，@三]; 
 NSArray * values = @ [@ 1，@ 2，@ 3]; 
 NSDictionary * dict = [[NSDictionary alloc] initWithObjects：值为Keys：keys]; 
  

当然，我可以通过两个数组迭代一个计数器，使用 var dict：[String：Int] 并逐步添加内容。但这似乎不是一个好的解决方案。使用 zip 和枚举可能是更好的方法来同时迭代两者。然而，这种方法意味着拥有一个可变字典，而不是一个不可变的字典。

  let keys = [one，two three] 
 let values = [1，2，3] 
 // ??? 
 let dict：[String：Int] = [one：1，two：2，three：3] //预期结果
  

解决方案

使用 zip 和 reduce ：

  let dict = zip（keys，values）.reduce（[String： Int]（））{var d = $ 0; d [$ 1.0] = $ 1.1;返回d} 
  

您可以缩短 reduce 通过为字典和元组 + >：

  func +< K，V>（lhs：[K：V]，rhs：（K，V） ） - > [K：V] {
 var result = lhs 
 result [rhs.0] = rhs.1 
 return result 
} 
 
 let dict = zip（键，值）.reduce（[String：Int]（），combine：+）
  

Is there an equivalent for Swift's native Dictionary to [NSDictionary initWithObjects: forKeys:]?

Say I have two arrays with keys and values and want to put them in a dictionary. In Objective-C I'd do it like this:

NSArray *keys = @[@"one", @"two", @"three"];
NSArray *values = @[@1, @2, @3];
NSDictionary *dict = [[NSDictionary alloc] initWithObjects: values forKeys: keys];

Of course I can iterate with a counter through both arrays, use a var dict: [String:Int] and add stuff step by step. But that doesn't seem to be a good solution. Using zip and enumerate are probably better ways of iterating over both at the same time. However this approach means having a mutable dictionary, not an immutable one.

let keys = ["one", "two", "three"]
let values = [1, 2, 3]
// ???
let dict: [String:Int] = ["one":1, "two":2, "three":3] // expected result

解决方案

A one-liner, using zip and reduce:

let dict = zip(keys, values).reduce([String:Int]()){ var d = $0; d[$1.0] = $1.1; return d }

You can shorten the reduce expression by defining the + operator for a Dictionary and a tuple:

func +<K,V>(lhs: [K:V], rhs: (K, V)) -> [K:V] {
    var result = lhs
    result[rhs.0] = rhs.1
    return result
}

let dict = zip(keys, values).reduce([String:Int](), combine: +)

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