【Swift學習】Swift編程之旅---集合類型之Dictionaries（八），swiftdictionaries

【Swift學習】Swift編程之旅---集合類型之Dictionaries（八），swiftdictionaries

　　字典是一種儲存相同類型多重資料的儲存空間。每個值（value）都關聯獨特的鍵（key），鍵作為字典中的這個值資料的標識符。和數組中的資料項目不同，字典中的資料項目並沒有具體順序。

　　字典寫作Dictionary<Key, Value>。也可以寫作[Key: Value]

 

　　建立空字典

var namesOfIntegers = [Int: String]()// namesOfIntegers is an empty [Int: String] dictionary

 

　　類型推斷寫作[:]

namesOfIntegers[16] = "sixteen"// namesOfIntegers now contains 1 key-value pairnamesOfIntegers = [:]// namesOfIntegers is once again an empty dictionary of type [Int: String]

 

 

　　建立字典字面量

[key 1: value 1, key 2: value 2, key 3: value 3]

var airports: [String: String] = ["YYZ": "Toronto Pearson", "DUB": "Dublin"]

 

　　類型推斷寫作

var airports = ["YYZ": "Toronto Pearson", "DUB": "Dublin"]

 

 

　　訪問和修改

　　count返回字典的索引值對數

　　isEmpty判斷字典是否為空白

　　

airports["LHR"] = "London Heathrow

 

 

if let oldValue = airports.updateValue("Dublin Airport", forKey: "DUB") {    print("The old value for DUB was \(oldValue).")}// Prints "The old value for DUB was Dublin.

 

 

　　removeValueForKey(_:)刪除索引值對  

if let removedValue = airports.removeValueForKey("DUB") {    print("The removed airport's name is \(removedValue).")} else {    print("The airports dictionary does not contain a value for DUB.")}// Prints "The removed airport's name is Dublin Airport.

 

 

 遍曆

for (airportCode, airportName) in airports {    print("\(airportCode): \(airportName)")}// YYZ: Toronto Pearson// LHR: London Heathrow

 

 

for airportCode in airports.keys {    print("Airport code: \(airportCode)")}// Airport code: YYZ// Airport code: LHR for airportName in airports.values {    print("Airport name: \(airportName)")}// Airport name: Toronto Pearson// Airport name: London Heathrow