Swift - 区间运算符（... 和 ..<）

区间运算符可以用来表示两个操作数之间的范围集合。\

1，闭区间运算符：a...b

for iCount in 512...1024{
     //从512遍历到1024（包括1024）
}

2，半闭区间运算符：a..<b

var fruts = ["apple","orange","banana"]
let iCount = fruts.count
for i in 0..<iCount{
    print("第\(i+1)个水果是\(fruts[i])")
}

3，倒序循环

通过 reversed() 方法，我们可以将一个正序循环变成逆序循环。

for i in (0..<10).reversed() {
    print(i)
}

4，字符串范围也可以使用区间运算符

//字符串截取
let words = "Hangge.com"

//字符串截取
let index = words.index(words.startIndex, offsetBy: 4)
let index2 = words.index(words.startIndex, offsetBy: 6)
let range1 = Range(uncheckedBounds: (lower: index, upper: index2))
let rangeStr1 = words.substring(with: range1) //ge
let newRangeStr1 = words[..<index]
let newRangeStr2 = words[index...]
let newRangeStr3 = words[range1]
print(rangeStr1)
 
//使用区间运算符
let range2 = words.index(words.startIndex, offsetBy: 4)..<words.index(words.startIndex,
                                                                      offsetBy: 6)
let rangeStr2 = words.substring(with: range2) //ge
let newRangeStr4 = words[range2]
print(rangeStr2)

5，区间运算符除了返回一个Range外，还可以接受Comparable的输入，返回ClosedInterval或HalfOpenInterval

所以我们可以用这个特性检查字符串里的字符是不是都是合法字符（比如是不是都是小写）

let words = "Hangge.com"
let interval = "a"..."z"
print(type(of: interval))

for c in words {
    if !interval.contains(String(c)){
            print("\(c)不是小写字母")
    }
}