substring在swift中的對應(yīng)方法
1.截取前幾位字符
let string = "abcdef1234.pdf"
let prefix = string.prefix(3)
print(prefix)
//打印結(jié)果：abc
2.截取后幾位字符
let string = "abcdef1234.pdf"
let suffix = string.suffix(3)
print(suffix)
//打印結(jié)果：pdf
3.去掉前幾位字符
let string = "abcdef1234.pdf"
let dropfirst = string.dropFirst(3)
print(dropfirst)
//打印結(jié)果：def1234.pdf
4.去掉后幾位字符
let string = "abcdef1234.pdf"
let dropLast = string.dropLast(4)
print(dropLast)
//打印結(jié)果：abcdef1234
5.截取字符串中間的字符
let string = "abcdef1234.pdf"
let numStr = string.dropFirst(6).prefix(4)
print(numStr)
//或者
if let index1 = string.lastIndex(of: "1"),
let index2 = string.lastIndex(of: "4") {
let num = String(string[index1...index2])
print(num)
}
//打印結(jié)果：1234
