我有以下简单的代码写在Swift 3:
let str = "Hello, playground"
let index = str.index(of: ",")!
let newStr = str.substring(to: index)
在Xcode 9 beta 5中，我得到了以下警告:
'substring(to:)'已弃用:请使用带有'partial range from'操作符的字符串切片下标。
这个部分范围的切片下标如何在Swift 4中使用?
当前回答
Swift 4/5更短:
let string = "123456"
let firstThree = String(string.prefix(3)) //"123"
let lastThree = String(string.suffix(3)) //"456"
其他回答
你可以使用扩展类String来创建你的自定义subString方法，如下所示:
extension String {
func subString(startIndex: Int, endIndex: Int) -> String {
let end = (endIndex - self.count) + 1
let indexStartOfText = self.index(self.startIndex, offsetBy: startIndex)
let indexEndOfText = self.index(self.endIndex, offsetBy: end)
let substring = self[indexStartOfText..<indexEndOfText]
return String(substring)
}
}
我写了一个字符串扩展替换' string: subString:'
extension String {
func sliceByCharacter(from: Character, to: Character) -> String? {
let fromIndex = self.index(self.index(of: from)!, offsetBy: 1)
let toIndex = self.index(self.index(of: to)!, offsetBy: -1)
return String(self[fromIndex...toIndex])
}
func sliceByString(from:String, to:String) -> String? {
//From - startIndex
var range = self.range(of: from)
let subString = String(self[range!.upperBound...])
//To - endIndex
range = subString.range(of: to)
return String(subString[..<range!.lowerBound])
}
}
用法:“日期(1511508780012+0530)”sliceByString(from: "("， to: "+") 示例结果:"1511508780012"
PS:可选选项被强制展开。如有需要，请添加类型安全检查。
这就是我的解，没有警告，没有错误，但很完美
let redStr: String = String(trimmStr[String.Index.init(encodedOffset: 0)..<String.Index.init(encodedOffset: 2)])
let greenStr: String = String(trimmStr[String.Index.init(encodedOffset: 3)..<String.Index.init(encodedOffset: 4)])
let blueStr: String = String(trimmStr[String.Index.init(encodedOffset: 5)..<String.Index.init(encodedOffset: 6)])
希望对大家有所帮助。
extension String {
func getSubString(_ char: Character) -> String {
var subString = ""
for eachChar in self {
if eachChar == char {
return subString
} else {
subString += String(eachChar)
}
}
return subString
}
}
let str: String = "Hello, playground"
print(str.getSubString(","))
编程时，我经常用简单的A-Za-z和0-9组成的字符串。不需要困难的索引操作。这个扩展是基于普通的老左/中/右函数。
extension String {
// LEFT
// Returns the specified number of chars from the left of the string
// let str = "Hello"
// print(str.left(3)) // Hel
func left(_ to: Int) -> String {
return "\(self[..<self.index(startIndex, offsetBy: to)])"
}
// RIGHT
// Returns the specified number of chars from the right of the string
// let str = "Hello"
// print(str.left(3)) // llo
func right(_ from: Int) -> String {
return "\(self[self.index(startIndex, offsetBy: self.length-from)...])"
}
// MID
// Returns the specified number of chars from the startpoint of the string
// let str = "Hello"
// print(str.left(2,amount: 2)) // ll
func mid(_ from: Int, amount: Int) -> String {
let x = "\(self[self.index(startIndex, offsetBy: from)...])"
return x.left(amount)
}
}
