swift * 字典/Dictionary初始化以及增、删、改、遍历

学习笔记

1、字典初始化

vardict = [:] //初始化无类型空字典

dict = ["1":"aaa","2":"bbb"]

print(dict)

dict = [1:"1","2":2]//key 和value都是不定类型的

print(dict)

       

let dict2:Dictionary<String,Int> = ["1":111,"2":222] //限定键值类型

print(dict2)

letdict3:[String:Int] = ["1":111]

print(dict3)

2、字典操作 

vardict4 = ["apple":"苹果","bag":"包"]
       

print(dict4["apple"])

dict4["apple"] ="橘子"//修改值

print(dict4)

dict4.updateValue("苹果", forKey: "apple")//更新键值如果key存在更新键值对并且返回key之前的对应的value

print(dict4)

print(dict4.updateValue("苹果", forKey: "apples")) //如果key不存在将增加新的键值对并返回nil

iflet origin = dict4.updateValue("aaaaa", forKey: "appl") {

     print("origin\(origin)")

           

}

print(dict4)

dict4["an"] == "一个" //增加/修改键值对

iflet origin = dict4.removeValueForKey("apple") {

     print("删除key\(origin)")//如果key存在删除对应的键值对 并返回key对应的值

     print(dict4)

}else {

           //不存在key返回nil字典不变

}

       

if let origin = dict4.removeValueForKey("aaaaa") {

     print(origin)

}else {

     print(dict4.removeValueForKey("aaaaa"))//如果key不存在不作操作并返回nil

}

print(dict4)

3、字典遍历

for(key,value) in dict4 {  //使用元组 遍历键值对

     print("\(key) : \(value)")

}

forkey indict4.keys{ //遍历所有key

     print(key)

}

forvalue indict4.values{ //遍历所有value

     print(value)

}