一、字典的定義

//可變字典，用泛型定義字典類型，當然類型定義可以省略
var dic11:Dictionary<Int,Int> = [0:1,1:2]
dic11[1] = 3     //修改字典內容
dic11    //[0: 1, 1: 3]

//不可變字典
let dic12:[String:Any] = ["a":4,"b":5,"c":6,"d":"1"]

二、字典元素的基本操作

• 任意值類型通常用 Any,而不是 NSObject

var dic21:[AnyHashable:Any] = [1:1,2:2,"a":"a","b":"b"]

• 增加元素

dic21["c"] = 3
dic21   //["b": "b", "a": "a", 2: 2, 1: 1, "c": 3]
dic21["a"] = 1
dic21   //["b": "b", "a": 1, 2: 2, 1: 1, "c": 3]

通過這種方式，如果字典中存在某個 鍵-值，就進行修改，如果不存在就進行添加此 鍵-值

• 刪除元素

dic21.removeValue(forKey: "a")

或

let index = dic21.index(forKey: "a")
dic21.remove(at: index!)

結果為：

dic21   //["b": "b", 2: 2, 1: 1, "c": 3]

• 改元素

dic21[2] = "b"
dic21   //["b": "b", 2: "b", 1: 1, "c": 3]
dic21.updateValue("a", forKey: 1)
dic21   //["b": "b", 2: "b", 1: "a", "c": 3]

• 查元素

dic21[1]    //"a"

三、 字典的基本操作

var dic31:[AnyHashable:Any] = [1:1,2:2,"a":"A","b":"B"]

• 字典的遍歷
• 遍歷所有鍵

for key in dic31.keys {
    print(key)
}

• 遍歷所有值

for value in dic31.values {
    print(value)
}

• 遍歷所有鍵值

for (key,value) in dic31 {
    print(key,value)
}

• 字典的合并，通過遍歷完成

var dic32:[AnyHashable:Any] = [1:2,2:3,"aa":"a","bb":"b"]
//將字典 dic31 和 dic32 合并，若有相同鍵，則保留 dic32 中的鍵值
for key in dic32.keys{
    dic31[key] = dic32[key]
}
dic31   //["b": "B", "a": "A", 2: 3, "aa": "a", 1: 2, "bb": "b"]

四、補充:擴展

extension Dictionary{
    static func + (dic1:inout Dictionary,dic2:inout Dictionary) -> Dictionary {
        for key in dic2.keys {
            dic1[key] = dic2[key]
        }
        return dic1
    }
}
var d4 = [1:1,2:"a"] as [Int : Any]
var d5:[Int : Any] = [3:1,4:2]
d4 + d5     //[2: "a", 3: 1, 1: 1, 4: 2]

兩個相加的字典 鍵值 類型必須要一致才可以。