Swift3 截取字符串

截取字符串

// 截取字符串
let str = "0123456789"

substring from

// substr from 从第4位开始截取
// 456789
str.substring(from: str.index(str.startIndex, offsetBy: 4))

substring to

// substr to 截取前3位
// 012
str.substring(to: str.index(str.startIndex, offsetBy: 3))

substring Range

index

// 第3位开始
let start = str.index(str.startIndex, offsetBy: 3)
// 倒数第二位
let end = str.index(str.endIndex, offsetBy: -2)
let result = str[start...end] //  3-8

// substr range
// range
let range = start ..< end
range.lowerBound // 3
range.upperBound // 8
str.substring(with: range) // 3-8

str[...start]              // 0-3
str.prefix(through: start)

str[start...]              // 3-9
str.suffix(from: start)

// 字符查找
let indofs = str.index(of: "2")!
var indofe = str.index(of: "8")!
// 截取
str[indofs...indofe] // 2-8
indofe = str.index(indofs, offsetBy: 2)
str[indofs...indofe] // 2-4

range of

// substr range 
let text = "0,2,4,6,"
// 从后到前找到第一个字符的range
let endRange = text.range(of: ",", options: .backwards, range: nil, locale: nil)
// 7
endRange?.lowerBound
// 8
endRange?.upperBound
// 根据 ..< 创建range
let searchRange = text.startIndex ..< (endRange?.lowerBound)!
// 0
searchRange.lowerBound
// 7
searchRange.upperBound
// 截取字符串
// 0,2,4,6
text.substring(with: searchRange)