Swift字典

字典的定义


var dict1 = ["swift":"雨燕","python":"大蟒","java":"爪哇国"]

//问题：dict1 长度是多少？ 3

var dict2:[String:String] = ["swift":"雨燕","python":"大蟒","java":"爪哇国"]

var dict3:Dictionary<String,String> = ["swift":"雨燕","python":"大蟒","java":"爪哇国"]

//空字典的定义

var empty1:[Int:String] = [:]

var empty2:Dictionary<String,String> = [:]

var empty3 = [String:String]()

基本操作:长度，判断是否为空，取值


print(dict1.count)

print(dict1.isEmpty)

print(dict1["java"]!)//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 d1 = [1:"a",2:"b",3:"d"]

let d2 = [2:"b",1:"a",3:"d"]

print(d1==d2)//true

//let d3 = [2:"b",1:"a",3:"d",3:"e"] --报错

遍历-遍历Key,value,key-value对


for key in dict1.keys{

    print(key)

}

for value in dict1.values{

    print(value)

}

for (key,value) in dict1{

    print(key,value)

}

增删改查


//如果这个Key当前没有，添加操作；如果当前这个Key存在，修改操作

//改

var user=["name":"miao","pwd":"123","job":"coder"]

user["job"] = "teacher"

print(user)

//user.updateValue("456",forKey:"pwd")//更新值

var oldPwd = user.updateValue("456",forKey:"pwd")!//返回原来value的值

if oldPwd == user["pwd"]{

    print("修改后的密码与修改前一样，可能会导致安全问题！")

}

print(user)

//添加

user["email"] = "56429@qq.com"

user.updateValue("chuzhou",forKey:"location")

print(user)

//删除

user.removeValue(forKey:"location")

user["email"] = nil //null

print(user)

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

//for in遍历

Swift字典

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