Swift Generics and Data Structures
Ch17.
泛型
17.1
泛型型態
兩數對調
佇列的運作
氣泡排序法
17.1.1
兩數對調
兩數對調先前已在函式那一章有討論過。
程式如下：
明明只是型態不同，
但要處理不同型態的對調，
卻要重新撰寫程
式，這效率
太低
。處理此問題與解決的方式
可以
使用所謂的泛型
型態的函式。
範例程式
part1
範例程式
part2
輸出結果
撰寫成泛型型態函式的步驟是先將不一樣的地方畫出，然後以
T
表示之，並且在函
式名稱後加上
<T>
這樣就大功告成了。
其中
T
是使用者自取的，當然也可以取別的名稱。
17.1.2
佇列的運作
佇列
(queue)
和堆疊
(stack)
是資料結構的重要主題，在此僅以佇
列為例
。
佇列就是排隊，先來的先服務
。
範例程式
part1
範例程式
part2
輸出結果
The integer queue has following elements:
100 200 300 400 500
After delete 100, the queue has following elements:
200 300 400 500
After insert 600, the queue has following elements:
200 300 400 500 600
17.2
型態限制
有時在處理泛型時，需要一些條件加進來才能處理，此稱為型態
的限制
(type constraint)
。
17.2.1
找某一值位於陣列的何處
以下是一找尋某一字串在字串陣列的位置，其片段程式如
下：
同理也可以將上述的程式改為整數
、
浮點數陣列
。
範例程式
part1
範例程式
part2
輸出結果
The index of Kiwi is Optional(3)
The index of Pineapple is nil
The index of 55 is Optional(4)
The index of 66 is nil
The index of 22.2 is Optional(1)
The index of 66.6 is nil
17.2.2
氣泡排序
氣泡排序是兩兩相比較，若是由小由大，表示當前一個值比後一
值大時，則必須交換，否則不變動。
範例程式
輸出結果
Before sorted:
10 30 5 7 2 8 18 12
After sorted:
2 5 7 8 10 12 18 30
17.3
關連型態
當定義協定時，有時宣告一或多個關連型態當做協定的定義很有
用。
一般關連型態以
associatedtype
關鍵字表示（
Swift 3
之前是
typealias
）。
範例程式
part1
範例程式
part2
輸出結果
陣列中有
5
個元素
100 200 300 400 500
刪除
100
後
，
陣列中有
4
個元素
200 300 400 500
加入
600
後
，
陣列中有
5
個元素
200 300 400 500 600
queueOfData[2] = 400
In this content, we explore Swift generics through examples of swapping integers, strings, and doubles using generic functions. We also delve into implementing a generic type for a queue data structure in Swift. The concepts are illustrated with code snippets and visual aids, making it easier to grasp the concepts.
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Presentation Transcript
17.1.1 // swap two integer numbers func swapInts(a: inout Int, b: inout Int) { let temp = a a = b b = temp }
part1 // swap using generic function func swapData<T>(a: inout T, b: inout T) { let temp = a a = b b = temp } var oneString = "Hello" var anotherString = "Swift" print("Before swapped: ") print("oneInt = \(oneString), anotherInt = \(anotherString) ") swapData(a: &oneString, b: &anotherString) print("After swapped: ") print("oneInt = \(oneString), anotherInt = \(anotherString) ") var oneInt = 100 var anotherInt = 200 print("Before swapped: ") print("oneInt = \(oneInt), anotherInt = \(anotherInt) ") swapData(a: &oneInt, b: &anotherInt) print("After swapped: ") print("oneInt = \(oneInt), anotherInt = \(anotherInt) ")
part2 var oneDouble = 123.456 var anotherDouble = 654.321 print("Before swapped: ") print("oneInt = \(oneDouble), anotherInt = \(anotherDouble) ") swapData(a: &oneDouble, b: &anotherDouble) print("After swapped: ") print("oneInt = \(oneDouble), anotherInt = \(anotherDouble) ")
Before swapped: oneInt = 100, anotherInt = 200 After swapped: oneInt = 200, anotherInt = 100 Before swapped: oneString = Hello, anotherString = Swift After swapped: oneString = Swift, anotherString = Hello Before swapped: oneInt = 123.456, anotherInt = 654.321 After swapped: oneInt = 654.321, anotherInt = 123.456
TT <T> T
17.1.2 (queue) (stack)
part1 // generic type struct Queue<T> { var items = [T]() mutating func insert(item: T) { items.append(item) } mutating func delete() -> T { return items.remove(at: 0) } } var queueOfInt = Queue<Int>() queueOfInt.insert(item: 100) queueOfInt.insert(item: 200) queueOfInt.insert(item: 300) queueOfInt.insert(item: 400) queueOfInt.insert(item: 500) print("The integer queue has following elements: ") for i in queueOfInt.items { print("\(i) ", terminator: "") } print("")
part2 queueOfInt.delete() print("After delete 100, the queue has following elements: ") for i in queueOfInt.items { print("\(i) ", terminator: "") } print("") queueOfInt.insert(item: 600) print("After insert 600, the queue has following elements: ") for i in queueOfInt.items { print("\(i) ", terminator: "") } print("\n")
The integer queue has following elements: 100 200 300 400 500 After delete 100, the queue has following elements: 200 300 400 500 After insert 600, the queue has following elements: 200 300 400 500 600
17.2 (type constraint)
17.2.1 func searchData(array: [String], valueToSearch: String) ->Int? { for (index, value) in array.enumerated() { if value == valueToSearch { return index } } return nil }
part1 func searchData<T: Equatable>(array: [T], valueToSearch : T) -> Int? { for (index, value) in array.enumerated() { if value == valueToSearch { return index } } return nil } print("The index of Kiwi is \(found)") let found2 = searchData(array: arrayofStrings, valueToSearch: "Pineapple") print("The index of Pineapple is \(found2)") let arrayOfInt = [11, 22, 33, 44, 55] let found3 = searchData(array: arrayOfInt, valueToSearch: 55) print("\nThe index of 55 is \(found3)") let found4 = searchData(array: arrayOfInt, valueToSearch: 66) print("The index of 66 is \(found4)") let arrayofStrings = ["Apple", "Guava", "Banana", "Kiwi", "Orange"] let found = searchData(array: arrayofStrings, valueToSearch: "Kiwi") let arrayOfDouble = [11.1, 22.2, 33.3, 44.4, 55.5] let found5 = searchData(array: arrayOfDouble, valueToSearch: 22.2)
part2 print("\nThe index of 22.2 is \(found5)") let found6 = searchData(array: arrayOfDouble, valueToSearch: 66.6) print("The index of 66.6 is \(found6)")
The index of Kiwi is Optional(3) The index of Pineapple is nil The index of 55 is Optional(4) The index of 66 is nil The index of 22.2 is Optional(1) The index of 66.6 is nil
//sorting integer numbers var arrOfInt = [10, 30, 5, 7, 2, 8, 18, 12] print("Before sorted: ") for i in arrOfInt { print("\(i) ", terminator: "") } arr[j] = arr[j+1] arr[j+1] = temp } } if flag == false { break } } func bubbleSort(arr: inout [Int]) { var flag: Bool for i in 0..<arr.count-1 { flag = false for j in 0..<arr.count-i-1 { if arr[j] > arr[j+1] { } bubbleSort(arr: &arrOfInt) print("\n\nAfter sorted: ") for j in arrOfInt { print("\(j) ", terminator: "") } print("") flag = true let temp = arr[j]
Before sorted: 10 30 5 7 2 8 18 12 After sorted: 2 5 7 8 10 12 18 30
17.3 associatedtype Swift 3 typealias
part1 protocol ExtraInformation { associatedtype ItemType var count: Int {get} subscript(i: Int) -> ItemType {get} } //comformance to the ExtraInformation Protocol typealias ItemType = T var count: Int { return items.count } subscript(i: Int) -> T { return items[i] } } struct QueueType<T>: ExtraInformation { var items = [T]() mutating func insert(item: T) { items.append(item) } mutating func delete() { items.remove(at: 0) }
part2 var queueOfData = QueueType<Int>() queueOfData.insert(item: 100) queueOfData.insert(item: 200) queueOfData.insert(item: 300) queueOfData.insert(item: 400) queueOfData.insert(item: 500) print(" \(queueOfData.count) ") for i in queueOfData.items { print("\(i) ", terminator: "") } print("\n") for i in queueOfData.items { print("\(i) ", terminator: "") } print("\n") queueOfData.insert(item: 600) print(" 600 \(queueOfData.count) ") for i in queueOfData.items { print("\(i) ", terminator: "") } print("\n") queueOfData.delete() print(" 100 \(queueOfData.count) ") print("queueOfData[2] = \(queueOfData[2])") print("")
5 100 200 300 400 500 100 4 200 300 400 500 600 5 200 300 400 500 600 queueOfData[2] = 400
