Strings and characters in swift
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This document provides an overview of strings and string handling in Swift. It discusses strings as collections of characters, encoding of strings in UTF-8, UTF-16 and UTF-32, properties of String and NSString like count and indexing, comparing strings using == and isEqual(to:), and considerations for equality of strings across encodings and decomposed character representations.
![StringProtocol NSString
import Foundation
// StringProtocol (NSString API)
let str = "Dog??"
let range = str.range(of: "?")!
print(range) // Index(_compoundOffset: 16, _cache:
Swift.String.Index._Cache.utf16)..<Index(_compoundOffset: 24, _cache:
Swift.String.Index._Cache.utf16)
print(str[..<range.lowerBound]) // Dog?
// NSString
let nsStr = str as NSString
let nsRange = nsStr.range(of: "?")
print(nsRange) // {4, 2}
print(nsStr.substring(to: nsRange.location)) // Dog?
// Range <-> NSRange
print(range == Range(nsRange, in: str)) // true
print(NSRange(range, in: str) == nsRange) // true](https://image.slidesharecdn.com/stringsandcharactersinswift-180210074602/85/Strings-and-characters-in-swift-28-320.jpg)
!["
"?" + [ZWJ] + "?" + [ZWJ] + "?" + [ZWJ] + "?"
"?" + [ZWJ] + "?" + [ZWJ] + "?" = "'"](https://image.slidesharecdn.com/stringsandcharactersinswift-180210074602/85/Strings-and-characters-in-swift-31-320.jpg)
Strings and characters in swift
- 10. String NSString
- 13. let ?
- 14. NSString ?
- 20. Unicode.UTF8 CodeUnit UInt8 Unicode.UTF16 CodeUnit UInt16 Unicode.UTF32 CodeUnit UInt32
- 21. String
- 22. ? "Dog??".count = 5 Character D U+0044 o U+006F g U+0067 ? U+203C ? U+1F436 Unicode Scalar (UTF-32) D U+0044 o U+006F g U+0067 ? U+203C ? U+1F436 0 1 2 3 4 UTF-16 0x44 0x6F 0x67 0x203C 0xD83D 0xDC36 0 1 2 3 4 5 UTF-8 0x44 0x6F 0x67 0xE2 0x80 0xBC 0xF0 0x9F 0x90 0xB6 0 1 2 3 4 5 6 7 8 9
- 23. ? " ? !?".count = 3 Character ? U+72AC U+20E3 U+0021 ? U+2047 Unicode Scalar (UTF-32) U+72AC ? U+20E3 ! U+0021 ? U+2047 0 1 2 3 UTF-16 0x72AC 0x20E3 0x21 0x2047 0 1 2 3 UTF-8 0xE7 0x8A 0xAC 0xE2 0x83 0xA3 0x21 0xE2 0x81 0x87 0 1 2 3 4 5 6 7 8 9
- 25. String NSString
- 26. String NSString
- 27. NSString NSString NSMutableString NSString StringProtocol NSUInteger NSRange String.Index Range
- 28. StringProtocol NSString import Foundation // StringProtocol (NSString API) let str = "Dog??" let range = str.range(of: "?")! print(range) // Index(_compoundOffset: 16, _cache: Swift.String.Index._Cache.utf16)..<Index(_compoundOffset: 24, _cache: Swift.String.Index._Cache.utf16) print(str[..<range.lowerBound]) // Dog? // NSString let nsStr = str as NSString let nsRange = nsStr.range(of: "?") print(nsRange) // {4, 2} print(nsStr.substring(to: nsRange.location)) // Dog? // Range <-> NSRange print(range == Range(nsRange, in: str)) // true print(NSRange(range, in: str) == nsRange) // true
- 29. String NSString
- 31. " "?" + [ZWJ] + "?" + [ZWJ] + "?" + [ZWJ] + "?" "?" + [ZWJ] + "?" + [ZWJ] + "?" = "'"
- 33. String NSString
- 35. "u{00E9}" == "u{0065}u{0301}" // "" == "e" + "?" "u{2460}" == "u{0031}" // " " == "1"
- 36. ==
- 37. "e" == "e" lhs rhs Character e U+0065 e U+0065 UnicodeScalar (UTF-32) e U+0065 e U+0065 D? (NFD) U+0065 U+0065 Swift == true NSString? isEqual: YES
- 38. "" == "e" + "?" lhs rhs Character U+00E9 U+0065 U+0301 UnicodeScalar (UTF-32) U+00E9 e U+0065 ? U+0301 D? (NFD) e U+0065 ? U+0301 e U+0065 ? U+0301 Swift == true NSString? isEqual: NO
- 39. " " == " " + " " lhs rhs Character U+304C U+304B U+0399 UnicodeScalar (UTF-32) U+304C U+304B U+0399 D? (NFD) U+304B U+0399 U+304B U+0399 Swift == true NSString? isEqual: NO
- 40. "?" == "e" + "?" + "_" lhs rhs Character ? U+00E9 U+0332 ? U+0065 U+0301 U+0332 UnicodeScalar (UTF-32) U+00E9 _ U+0332 e U+0065 ? U+0301 _ U+0332 D? (NFD) e U+0065 _ U+0332 ? U+0301 e U+0065 _ U+0332 ? U+0301 Swift == true NSString? isEqual: NO
- 41. " " == " " lhs rhs Character CJK U+FA10 CJK U+585A UnicodeScalar (UTF-32) U+FA10 U+585A D? (NFD) U+585A U+585A Swift == true NSString? isEqual: NO
- 42. " " == " " lhs rhs Character CJK U+FA11 CJK U+5D0E UnicodeScalar (UTF-32) U+FA11 U+5D0E D? (NFD) U+FA11 U+5D0E Swift == false NSString? isEqual: NO
- 43. " " == " " lhs rhs Character CJK U+585A U+585A U+E0100 UnicodeScalar (UTF-32) U+585A U+585A U+E0100 D? (NFD) U+585A U+585A U+E0100 Swift == false NSString? isEqual: NO
- 44. String NSString