【Swift學習】Swift編程之旅---集合類型之字典（八）

　　字典是一種存儲相同類型多重數據的存儲器。每一個值（value）都關聯獨特的鍵（key），鍵做爲字典中的這個值數據的標識符。和數組中的數據項不一樣，字典中的數據項並無具體順序。

　　字典寫做Dictionary<Key, Value>。也能夠寫做[Key: Value]

 

　　建立空字典

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

 

　　類型推斷寫做[:]

namesOfIntegers[16] = "sixteen" // namesOfIntegers now contains 1 key-value pair namesOfIntegers = [:] // 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"]

 

　　類型推斷寫做

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

 

 

　　訪問和修改

　　count返回字典的鍵值對數

　　isEmpty判斷字典是否爲空

　　

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(_:)刪除鍵值對  

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.

 

 

 遍歷

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