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
我使用的简单方法是:
String(Array(str)[2...4])
其他回答
快速4 5 5+
Last的子字符串
let str = "Hello World"
let removeFirstSix = String(str.dropFirst(6))
print(removeFirstSix) //World
来自First的子字符串
let removeLastSix = String(str.dropLast(6))
print(removeLastSix) //Hello
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)
}
}
substring(from: index)转换为[index…]
检查样品
let text = "1234567890"
let index = text.index(text.startIndex, offsetBy: 3)
text.substring(from: index) // "4567890" [Swift 3]
String(text[index...]) // "4567890" [Swift 4]
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(","))
如果你只是想获取一个特定字符的子字符串，你不需要先找到索引，你可以只使用prefix(while:)方法
let str = "Hello, playground"
let subString = str.prefix { $0 != "," } // "Hello" as a String.SubSequence
