我有以下用Swift 3编写的简单代码：
let str = "Hello, playground"
let index = str.index(of: ",")!
let newStr = str.substring(to: index)
从Xcode 9 beta 5，我得到以下警告：
'
substring(to:)'已被弃用：请使用String切片下标和'partial range from'运算符。
如何在Swift 4中使用具有部分范围的切片下标？
你应该将一边留空，因此名称为“部分范围”。
let newStr = str[..<index]
同样代表运营商的部分范围，只是将对方留空：
let newStr = str[index...]
请记住，这些范围运算符返回Substring。如果要将其转换为字符串，请使用String的初始化函数：
let newStr = String(str[..<index])
您可以阅读有关新子串here的更多信息。
let str : String = "ilike"
for i in 0...str.count {
let index = str.index(str.startIndex, offsetBy: i) // String.Index
let prefix = str[..<index] // String.SubSequence
let suffix = str[index...] // String.SubSequence
print("prefix \(prefix), suffix : \(suffix)")
}
prefix , suffix : ilike
prefix i, suffix : like
prefix il, suffix : ike
prefix ili, suffix : ke
prefix ilik, suffix : e
prefix ilike, suffix :
let substring1 = string[startIndex...endIndex] // including endIndex
let subString2 = string[startIndex..<endIndex] // excluding endIndex
您可以使用类String的扩展创建自定义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)
}
}
我已经写了一个字符串扩展名来替换'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：
"Date(1511508780012+0530)".sliceByString(from: "(", to: "+")Example Result “1511508780012”
PS：选择者被迫解开。请在必要时添加类型安全检查。
使用此方法，您可以获得特定范围的字符串。您需要传递开始索引，然后传递所需的字符总数。
extension String{
func substring(fromIndex : Int,count : Int) -> String{
let startIndex = self.index(self.startIndex, offsetBy: fromIndex)
let endIndex = self.index(self.startIndex, offsetBy: fromIndex + count)
let range = startIndex..<endIndex
return String(self[range])
}
}
在编程时，我经常使用简单的A-Za-z和0-9的字符串。无需困难的索引操作。此扩展程序基于普通的左/中/右功能。
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)
}
}
这是我的解决方案，没有警告，没有错误，但完美无缺
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)])
希望这会有所帮助： -
var string = "123456789"
如果你想在某个特定索引后面有一个子字符串。
var indexStart = string.index(after: string.startIndex )// you can use any index in place of startIndex
var strIndexStart = String (string[indexStart...])//23456789
如果你想在最后删除一些字符串后想要一个子字符串。
var indexEnd = string.index(before: string.endIndex)
var strIndexEnd = String (string[..<indexEnd])//12345678
您还可以使用以下代码创建索引： -
var indexWithOffset = string.index(string.startIndex, offsetBy: 4)
希望它会有所帮助。
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(","))
将子串（Swift 3）转换为字符串切片（Swift 4）
示例在Swift 3,4中：
let newStr = str.substring(to: index) // Swift 3
let newStr = String(str[..<index]) // Swift 4
let newStr = str.substring(from: index) // Swift 3
let newStr = String(str[index...]) // Swift 4
let range = firstIndex..<secondIndex // If you have a range
let newStr = = str.substring(with: range) // Swift 3
let newStr = String(str[range]) // Swift 4
let text = "Hello world"
text[...3] // "Hell"
text[6..<text.count] // world
text[NSRange(location: 6, length: 3)] // wor
import Foundation
extension String {
subscript(value: NSRange) -> Substring {
return self[value.lowerBound..<value.upperBound]
}
}
extension String {
subscript(value: CountableClosedRange<Int>) -> Substring {
get {
return self[index(at: value.lowerBound)...index(at: value.upperBound)]
}
}
subscript(value: CountableRange<Int>) -> Substring {
get {
return self[index(at: value.lowerBound)..<index(at: value.upperBound)]
}
}
subscript(value: PartialRangeUpTo<Int>) -> Substring {
get {
return self[..<index(at: value.upperBound)]
}
}
subscript(value: PartialRangeThrough<Int>) -> Substring {
get {
return self[...index(at: value.upperBound)]
}
}
subscript(value: PartialRangeFrom<Int>) -> Substring {
get {
return self[index(at: value.lowerBound)...]
}
}
func index(at offset: Int) -> String.Index {
return index(startIndex, offsetBy: offset)
}
}
Swift 4中的缩写：
var string = "123456"
string = String(string.prefix(3)) //"123"
string = String(string.suffix(3)) //"456"
您可以通过以下方式将代码转换为Swift 4：
let str = "Hello, playground"
let index = str.index(of: ",")!
let substr = str.prefix(upTo: index)
您可以使用以下代码获得一个新字符串：
let newString = String(str.prefix(upTo: index))
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]
一些有用的扩展：
extension String {
func substring(from: Int, to: Int) -> String {
let start = index(startIndex, offsetBy: from)
let end = index(start, offsetBy: to - from)
return String(self[start ..< end])
}
func substring(range: NSRange) -> String {
return substring(from: range.lowerBound, to: range.upperBound)
}
}
Swift4：
extension String {
func subString(from: Int, to: Int) -> String {
let startIndex = self.index(self.startIndex, offsetBy: from)
let endIndex = self.index(self.startIndex, offsetBy: to)
return String(self[startIndex...endIndex])
}
}
用法：
var str = "Hello, playground"
print(str.subString(from:1,to:8))
Swift3和Swift4中uppercasedFirstCharacter便利属性的示例。
属性uppercasedFirstCharacterNew演示了如何在Swift4中使用字符串切片下标。
extension String {
public var uppercasedFirstCharacterOld: String {
if characters.count > 0 {
let splitIndex = index(after: startIndex)
let firstCharacter = substring(to: splitIndex).uppercased()
let sentence = substring(from: splitIndex)
return firstCharacter + sentence
} else {
return self
}
}
public var uppercasedFirstCharacterNew: String {
if characters.count > 0 {
let splitIndex = index(after: startIndex)
let firstCharacter = self[..<splitIndex].uppercased()
let sentence = self[splitIndex...]
return firstCharacter + sentence
} else {
return self
}
}
}
let lorem = "lorem".uppercasedFirstCharacterOld
print(lorem) // Prints "Lorem"
let ipsum = "ipsum".uppercasedFirstCharacterNew
print(ipsum) // Prints "Ipsum"