import Foundation

//字典
//定義不可變字典

let dicta:[Int:String] = [1:"China",2:"Japan",3:"USA"]
if let dictavalue = dicta[3] {
    print(dictavalue)
}

//定義可變字典
var dictb:[String:String] = ["classa":"23","classb":"45","classc":"78"]
if let dictbvalue = dictb["classc"] {
    print(dictbvalue)
}

//定義字典型的另外一種方式

let dictc:Dictionary<Int,Int> = [2:20,3:30,4:40]
print(dictc[3])

var dictd:Dictionary<String,String> = ["a": "Award","b":"big"]
print(dictd["b"])

//字典的刪除

dictb.removeValue(forKey: "classb")
print(dictb)

//字典的新增一個值
dictb["classd"] = "899"
print(dictb)

//更新字典的值-方式一: 直接更新

dictb["classd"] = "1000"
print("now the dictb is: \(dictb)")

//更新字典的值-方式二：updateValue()

dictb.updateValue("2000", forKey: "classd")
print("now the dictb is changed to :\(dictb)")
 

輸出：

USA

78

Optional(30)

Optional("big")

["classa": "23", "classc": "78"]

["classd": "899", "classa": "23", "classc": "78"]

now the dictb is: ["classd": "1000", "classa": "23", "classc": "78"]

now the dictb is changed to :["classd": "2000", "classa": "23", "classc": "78"]

Program ended with exit code: 0