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@mediter mediter/range.swift
Last active Jul 31, 2019

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[NSRange v.s. Range<String.Index>] #swift #nsrange #range
https://stackoverflow.com/a/30404532
As of Swift 4 (Xcode 9), the Swift standard library provides methods to convert between Swift string ranges (Range<String.Index>) and NSString ranges (NSRange). Example:
let str = "a👿b🇩🇪c"
let r1 = str.range(of: "🇩🇪")!
// String range to NSRange:
let n1 = NSRange(r1, in: str)
print((str as NSString).substring(with: n1)) // 🇩🇪
// NSRange back to String range:
let r2 = Range(n1, in: text)!
print(str.substring(with: r2)) // 🇩🇪
Therefore the text replacement in the text field delegate method can now be done as
func textField(_ textField: UITextField,
shouldChangeCharactersIn range: NSRange,
replacementString string: String) -> Bool {
if let oldString = textField.text {
let newString = oldString.replacingCharacters(in: Range(range, in: oldString)!,
with: string)
// ...
}
// ...
}
(Older answers for Swift 3 and earlier:)
As of Swift 1.2, String.Index has an initializer
init?(_ utf16Index: UTF16Index, within characters: String)
which can be used to convert NSRange to Range<String.Index> correctly (including all cases of Emojis, Regional Indicators or other extended grapheme clusters) without intermediate conversion to an NSString:
extension String {
func rangeFromNSRange(nsRange : NSRange) -> Range<String.Index>? {
let from16 = advance(utf16.startIndex, nsRange.location, utf16.endIndex)
let to16 = advance(from16, nsRange.length, utf16.endIndex)
if let from = String.Index(from16, within: self),
let to = String.Index(to16, within: self) {
return from ..< to
}
return nil
}
}
This method returns an optional string range because not all NSRanges are valid for a given Swift string.
The UITextFieldDelegate delegate method can then be written as
func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
if let swRange = textField.text.rangeFromNSRange(range) {
let newString = textField.text.stringByReplacingCharactersInRange(swRange, withString: string)
// ...
}
return true
}
The inverse conversion is
extension String {
func NSRangeFromRange(range : Range<String.Index>) -> NSRange {
let utf16view = self.utf16
let from = String.UTF16View.Index(range.startIndex, within: utf16view)
let to = String.UTF16View.Index(range.endIndex, within: utf16view)
return NSMakeRange(from - utf16view.startIndex, to - from)
}
}
A simple test:
let str = "a👿b🇩🇪c"
let r1 = str.rangeOfString("🇩🇪")!
// String range to NSRange:
let n1 = str.NSRangeFromRange(r1)
println((str as NSString).substringWithRange(n1)) // 🇩🇪
// NSRange back to String range:
let r2 = str.rangeFromNSRange(n1)!
println(str.substringWithRange(r2)) // 🇩🇪
Update for Swift 2:
The Swift 2 version of rangeFromNSRange() was already given by Serhii Yakovenko in this answer, I am including it here for completeness:
extension String {
func rangeFromNSRange(nsRange : NSRange) -> Range<String.Index>? {
let from16 = utf16.startIndex.advancedBy(nsRange.location, limit: utf16.endIndex)
let to16 = from16.advancedBy(nsRange.length, limit: utf16.endIndex)
if let from = String.Index(from16, within: self),
let to = String.Index(to16, within: self) {
return from ..< to
}
return nil
}
}
The Swift 2 version of NSRangeFromRange() is
extension String {
func NSRangeFromRange(range : Range<String.Index>) -> NSRange {
let utf16view = self.utf16
let from = String.UTF16View.Index(range.startIndex, within: utf16view)
let to = String.UTF16View.Index(range.endIndex, within: utf16view)
return NSMakeRange(utf16view.startIndex.distanceTo(from), from.distanceTo(to))
}
}
Update for Swift 3 (Xcode 8):
extension String {
func nsRange(from range: Range<String.Index>) -> NSRange {
let from = range.lowerBound.samePosition(in: utf16)
let to = range.upperBound.samePosition(in: utf16)
return NSRange(location: utf16.distance(from: utf16.startIndex, to: from),
length: utf16.distance(from: from, to: to))
}
}
extension String {
func range(from nsRange: NSRange) -> Range<String.Index>? {
guard
let from16 = utf16.index(utf16.startIndex, offsetBy: nsRange.location, limitedBy: utf16.endIndex),
let to16 = utf16.index(utf16.startIndex, offsetBy: nsRange.location + nsRange.length, limitedBy: utf16.endIndex),
let from = from16.samePosition(in: self),
let to = to16.samePosition(in: self)
else { return nil }
return from ..< to
}
}
Example:
let str = "a👿b🇩🇪c"
let r1 = str.range(of: "🇩🇪")!
// String range to NSRange:
let n1 = str.nsRange(from: r1)
print((str as NSString).substring(with: n1)) // 🇩🇪
// NSRange back to String range:
let r2 = str.range(from: n1)!
print(str.substring(with: r2)) // 🇩🇪
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