swift-字典

字典的定义

var dict1 = ["name":"张三","hobby":"运动","sex":"男"] 
//dict1 长度是3
var dict2:[String:String] =  ["name":"张三","hobby":"运动","sex":"男"]  
var dict3:Dictionary<String,String> =  ["name":"张三","hobby":"运动","sex":"男"] 
//空字典的定义
var empty1:[Int:String] = [:]
var empty2:Dictionary<String,String> = [:]
var empty3 = [String:String]()

基本操作: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:无序、key不能重复
let d1 = [1:"a",2:"b",3:"d"]
let d2 = [2:"b",1:"a",3:"d"]
print(d1==d2)//true 

遍历

//遍历Key
for key in dict1.keys{
    print(key)
}
//遍历value
for value in dict1.values{
    print(value)
}
//遍历key-value对
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
//增
user["email"] = "12345@qq.com"
user.updateValue("bengbu",forKey:"location")
print(user)
//删
user.removeValue(forKey:"location")
user["email"] = nil //null
print(user)
//改
var user=["name":"gao","pwd":"123","job":"student"]
user["job"] = "coder"
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)