//4.以某一特定位置来截取字符串

var string = " https://www.baidu.com"

let range = string.range(of: "baidu")

let lowerStr = string.substring(to: (range?.lowerBound)!)

//结果为： https://www.

print("to lower string: \(lowerStr)")

let upperStr = string.substring(to: (range?.upperBound)!)

//结果为： https://www.baidu

print("to upper string: \(upperStr)")

let lowerStr2 = string.substring(from: (range?.lowerBound)!)

//结果为： baidu.com

print("from lower string: \(lowerStr2)")

let upperStr2 = string.substring(from: (range?.upperBound)!)

//结果为： .com

print("from upper string: \(upperStr2)")

lowerBound与upperBound