swift * 字典/Dictionary初始化以及增、删、改、遍历

学习笔记

1、字典初始化

var dict = [:] //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)

let dict3:[String:Int] = ["1":111]

print(dict3)

2、字典操作

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

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

print("origin \(origin)")

}

print(dict4)

dict4["an"] == "一个" //增加/修改键值对

if let 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

} else {

//不存在key 返回nil 字典不变

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

print(origin)

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)")

for key in dict4.keys { //遍历所有key

print(key)

for value in dict4.values { //遍历所有value

print(value)

}