Swift - 区间运算符（... 和 ..<）

1、闭区间运算符：a...b

for i 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 frutsCount = fruts.count
for i in 0..< frutsCount{
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。(输出结果：3、2、1、0)

for i in (0..<4).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"
//不使用区间运算符
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
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
print(rangeStr2)