Swift-字典

字典的创建

var dict1:[Int:String] = [1:"One", 2:"Two", 3:"Three"]
var dict2:[String:String] = [1:"One", 2:"Two", 3:"Three"] 
var dict3:Dictionary<String,String> = [1:"One", 2:"Two", 3:"Three"]

空字典的定义

var empty1:[Int:String] = [:]
var empty2:Dictionary<String,String> = [:]
var empty3 = [String:String]()

判断字典的长度

print(dict1.count)

判断字典是否为空

print(dict1.isEmpty)

字典的特点

1.字典是无序的 2.字典的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 

遍历字典

//key
for key in dict1.keys{
    print(key)
}

//value
for value in dict1.values{
    print(value)
}

//key-value
for (key,value) in dict1{
    print(key,value)
}

//enumerated
for (key, value) in dict1.enumerated() {
    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
var user=["name":"zhangsan","pwd":"123456","job":"student"]

添加

user["sex"] = "man"
user.updateValue("huainan",forKey:"location")
print(user)

删除

user.removeValue(forKey:"location")
user["sex"] = nil //null
print(user)

修改

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