swift之字典

1、字典的定义

//方法一

let dict1 = ["a":12,"b":13]

//方法二

//如果key-value 的数据类型不一致用以下方法

let dict2 = ["name":"张","age":18] as [String : Any]

上面定义字典省略了Dictionary<String,Int>

//方法三

let dict3:Dictionary<String,Int> = ["a":12,"b":14]

//方法四

let dict4:[Int:String] = ["a":12,"b":13,"c":14]

2、空字典的定义

//第一种

var dict1:[Int:String]=[:]

//第二种

var dict2:Dictionary=[:]

//第三种

var dict13=[Int:String]()

3、基本操作

var dict1=["a":12,"b":13,"c":14]

print(dict1.count)        //打印数组长度

print(dict1.isEmpty)     //判断值是否为空

print(dict1[1]!)               //取值 (返回值是一个可选型，通过!进行解包)

//字典的特点:

1)无序

2)键不能重复

let dict1=["a":12,"b":13,"c":14]

let dict2=["a":12,"c":14,"b":13]

print(dict1==dict2)//判断是否一致

4、遍历

let dict:Dictionary<String,Any> = ["name":"张三","age":14,"title":"老板"]

//遍历元组 

let e: (key: String, value: Any)

for e in dict {

    print("\(e.key) \(e.value)")

}

方法二

print("-------同时遍历key和value")

for (kkk,vvv) in dict {

        print("\(kkk) \(vvv)")

}

//enumerated() 枚举

print("-------同时遍历key和value和索引")

for (kkk,vvv) in dict.enumerated() {

    print("\(kkk) \(vvv)")

}

5、增删改查

往字典里面增加一个元素

var dict = ["name":"张三","age":18] as [String : Any]

    dict["title"] = "李四"

    print(dict)

字典里面修改一个元素

var dict = ["name":"张三","age":18] as [String : Any]

//    dict["title"] = "李四"

      dict["name"]="王老五"

      print(dict)

//如果key存在就是修改，不存在就是新增。

字典里面删除一个元素

var dict = ["name":"张三","age":18] as [String : Any]

//方法一

//找到元素所在的位置

if let index = dict.index(forKey: "age") {

//删除这个位置对应的元素

let olditem = dict.remove(at: index)

}

print(dict)

//方法二

var dict = ["name":"张三","age":18] as [String : Any]

      dict.removeValue(forKey: "age")

      print(dict)

总结：什么时候我们采用哪种类型？

数组：有序的；

set: 无序、唯一性、交集并集等集合专有的操作速度高

字典：key-value对

swift之字典

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