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?
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
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)
}
}
其他回答
Swift 4/5更短:
let string = "123456"
let firstThree = String(string.prefix(3)) //"123"
let lastThree = String(string.suffix(3)) //"456"
var str = "Hello, playground"
let indexcut = str.firstIndex(of: ",")
print(String(str[..<indexcut!]))
print(String(str[indexcut!...]))
你可以试着用这种方法,并会得到适当的结果。
希望这将帮助更多:-
var string = "123456789"
如果你想在某个特定的索引后面加一个子字符串。
var indexStart = string.index(after: string.startIndex )// you can use any index in place of startIndex
var strIndexStart = String (string[indexStart...])//23456789
如果你想在末尾删除某个字符串后获得子字符串。
var indexEnd = string.index(before: string.endIndex)
var strIndexEnd = String (string[..<indexEnd])//12345678
还可以使用以下代码创建索引:—
var indexWithOffset = string.index(string.startIndex, offsetBy: 4)
我使用的简单方法是:
String(Array(str)[2...4])
Swift 5,4
使用
let text = "Hello world"
text[0] // H
text[...3] // "Hell"
text[6..<text.count] // world
text[NSRange(location: 6, length: 3)] // wor
Code
import Foundation
public extension String {
subscript(value: Int) -> Character {
self[index(at: value)]
}
}
public extension String {
subscript(value: NSRange) -> Substring {
self[value.lowerBound..<value.upperBound]
}
}
public extension String {
subscript(value: CountableClosedRange<Int>) -> Substring {
self[index(at: value.lowerBound)...index(at: value.upperBound)]
}
subscript(value: CountableRange<Int>) -> Substring {
self[index(at: value.lowerBound)..<index(at: value.upperBound)]
}
subscript(value: PartialRangeUpTo<Int>) -> Substring {
self[..<index(at: value.upperBound)]
}
subscript(value: PartialRangeThrough<Int>) -> Substring {
self[...index(at: value.upperBound)]
}
subscript(value: PartialRangeFrom<Int>) -> Substring {
self[index(at: value.lowerBound)...]
}
}
private extension String {
func index(at offset: Int) -> String.Index {
index(startIndex, offsetBy: offset)
}
}