Swift String Cheat Sheet | Hacker News Reader

Swift String Cheat Sheet

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63 pointsingve7 comments

  > Swift is Unicode correct so the equality operator (“==”) checks 
  > for Unicode canonical equivalence.

I think this is what this implies, but does Swift do grapheme canonicalization/normalization here? And which one? It might be worth adding the "Noël problem" here.

Yes, I believe so. From here: https://developer.apple.com/library/ios/documentation/Swift/...

"Every instance of Swift’s Character type represents a single extended grapheme cluster. An extended grapheme cluster is a sequence of one or more Unicode scalars that (when combined) produce a single human-readable character."

And then later:

"For example, LATIN SMALL LETTER E WITH ACUTE (U+00E9) is canonically equivalent to LATIN SMALL LETTER E (U+0065) followed by COMBINING ACUTE ACCENT (U+0301). Both of these extended grapheme clusters are valid ways to represent the character é, and so they are considered to be canonically equivalent"

Nice, thank you for the reference.

According to my (admittedly limited) understamding of Unicode, they did almost everything correctly. The only issue I see is with the 'uppercase'/'lowercase' functions, which use algorithms that depend on locale; I wonder which locale Swift assumes (hopefully not some global one...).

Those are (or were, at least) bridged from NSString. There's a bunch of path handling stuff available as well, because Swift String can be converted to and from NSString.

You can use the lowercaseStringWithLocale/uppercaseStringWithLocale methods to explicitly specify which locale to use: https://developer.apple.com/library/ios/documentation/Cocoa/...:

A couple missing useful things to know how to do are split, join, and trim, which I have on a page:

http://www.h4labs.com/dev/ios/swift_cookbook.html?topic=stri...

Something that's not on either page but if you use SQLite, it's important to be able to convert a C string:

let str:String = String.fromCString(UnsafePointer<CChar>(sqlite3_column_text(statement, columnCtr)))!

Make sure you don't have NULL columns.

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