在字典中交换值的键？

I have an dictionary in Swift that looks like this:

我在Swift中有一个字典，如下所示：

[
    0: "82",
    1: "12",
    2: "3",
    3: "42"
    // Etc.
]

And let's say I want to swap the keys for values 82 and 3, so the new dictionary looks like this:

并且假设我想将键交换为值82和3，因此新词典如下所示：

[
    0: "3",
    1: "12",
    2: "82",
    3: "42"
    // Etc.
]

How would I do this? (I have found no tips and have no idea how to go about doing this, so I have no code I've tried with this)

我该怎么办？（我没有找到任何提示，也不知道如何去做，所以我没有尝试过这个代码）

EDIT:

编辑：

I just did this:

我这样做了：

var first_key = 0
var second_key = 2
var first_value = dict[first_key]!
var second_value = dict[second_key]!
dict[first_key] = second_value
dict[second_key] = first_value

4 个解决方案

#1

The basic idea is to create a temporary variable to hold one of the values when you exchange them.

基本思想是创建一个临时变量来在交换时保存其中一个值。

let tmp = dict[0]
dict[0] = dict[2]
dict[2] = tmp

Or you can use the global swap function for this (which does the same thing internally).

或者您可以使用全局交换功能（在内部执行相同的操作）。

var dict = [
    0: "82",
    1: "12",
    2: "3",
    3: "42"
]

swap(&dict[0], &dict[2])

#2

When you have to swap variables, the simplest way is by using tuples.

当你必须交换变量时，最简单的方法是使用元组。

If you want to swap x and y:

如果你想交换x和y：

(x, y) = (y, x)

In your case:

在你的情况下：

(dict[0], dict[2]) = (dict[2], dict[0])

#3

You can do some thing like this to simply swap the values,

你可以做这样的事情来简单地交换价值，

var dict = [
    0: "82",
    1: "12",
    2: "3",
    3: "42"
    // Etc.
]
if  let value = dict[key], let existingValue = dict[newKey] {
    dict[key] = existingValue
    dict[newKey] = value
}

Now, the value of dict is new, with the values you wanted. Or, you could also add category on Dictionary like this,

现在，dict的值是新的，带有你想要的值。或者，你也可以像这样在Dictionary上添加类别，

extension Dictionary {
    mutating func swap(key1: Key, key2: Key) {
        if  let value = self[key1], let existingValue = self[key2] {
            self[key1] = existingValue
            self[key2] = value
        }

    }
}


dict.swap(0, key2: 2)
print(dict)

Notice, you dont really need to pass a pointer.

注意，你真的不需要传递指针。

#4

var random = ["LAX":"Los Angeles", "JFK":"New York"]


func flip <T, U>(_ dictionary: Dictionary<U, T>) -> Dictionary<T, U> {

 
    let arrayOfValues: [T] = Array(dictionary.values)
    let arrayOfKeys: [U] = Array(dictionary.keys)

    var newDictionary: [T: U] = [:]
    
    for i in 0...arrayOfValues.count-1 {
       
        newDictionary[arrayOfValues[i]] = arrayOfKeys[i]
        
    }
    
    return newDictionary
    
}

flip(random) // You will get ["Los Angeles": "LAX", "New York": "JFK"]

#1