Swift 范圍運算符

Swift 4支持幾種類型的范圍操作符，用于簡潔地表示一系列數值。愛掏網 - it200.com

• 閉區間操作符
• 半開區間操作符
• 單側區間

閉合范圍運算符（a…b）指定了從a到b的范圍（包括a和b，且a的值不應大于b的值）。愛掏網 - it200.com閉合范圍運算符在需要迭代一個范圍，并且希望使用所有值（例如在for-in循環中）時非常有用。愛掏網 - it200.com

示例

for index in 1...10 {  
    print("\(index) times 5 is \(index * 5)")  
}  

輸出:

1 times 5 is 5
2 times 5 is 10
3 times 5 is 15
4 times 5 is 20
5 times 5 is 25
6 times 5 is 30
7 times 5 is 35
8 times 5 is 40
9 times 5 is 45
10 times 5 is 50

半開區間操作符

半開放范圍運算符（a..<b）指定了從a到b的范圍，但不包括b。愛掏網 - it200.com它被稱為半開放范圍運算符，因為它包含第一個值，但不包含最后一個值。愛掏網 - it200.com與閉合范圍運算符類似，半開放范圍運算符中a的值也不能大于b的值。愛掏網 - it200.com如果a的值等于b，則結果范圍將為空。愛掏網 - it200.com

半開放范圍運算符通常與數組一起使用，用于計算列表的長度。愛掏網 - it200.com

示例

let names = ["Albert", "Aryan", "Ajeet", "Jill"]  
let count = names.count  
for i in 0..<count {  
    print("Person \(i + 1) name is \(names[i])")  
}  

輸出:

Person 1 name is Albert
Person 2 name is Aryan
Person 3 name is Ajeet
Person 4 name is Jill

單側區間

單側范圍運算符是閉合范圍運算符或半開放范圍運算符在單個方向上的替代形式。愛掏網 - it200.com

示例1

let names = ["Albert", "Aryan", "Ajeet", "Jill"]  
let count = names.count  
for name in names[2...] {  
    print(name)  
} 

輸出:

Ajeet
Jill

示例2

let names = ["Albert", "Aryan", "Ajeet", "Jill"]  
let count = names.count  
for name in names[...2] {  
    print(name)  
}  

輸出:

Albert
Aryan
Ajeet

示例3

let names = ["Albert", "Aryan", "Ajeet", "Jill"]  
let count = names.count  
for name in names[..<2] {  
    print(name)  
}  

輸出:

Albert
Aryan