On Apr 2, 2015, at 04:54 , Charles Jenkins <cejw...@gmail.com> wrote:
> Swift has a built-in func stringByTrimmingCharactersInSet(set: > NSCharacterSet) -> String There is something wacky going on here — or not. (I know you don’t want to use this particular method, but I’m just using it as an example.) First of all, String and NSString are different classes, for real. Quoting a god-like personage, in a recent thread: > On Mar 23, 2015, at 13:52 , Greg Parker <gpar...@apple.com> wrote: > >> Most of NSString's methods are re-implemented in a Swift extension on class >> String. You get this extension when you `import Cocoa`. And indeed, if you try this in a playground: > let strA = "Hello, string" > let strB = "Hello, NSString" as NSString > let a = strA.characterAtIndex (6) // line 3 > let b = strB.characterAtIndex (6) // line 4 you get an error at line 3, as you would expect/hope (since Strings aren’t “made of” unichars), but no error in line 4 (since NSStrings are). So it’s not odd that String.stringByTrimmingCharactersInSet would return a String. What’s very odd is that *in Swift* NSString.stringByTrimmingCharactersInSet returns a String — not a NSString — as does NSAttributedString.string, or apparently any Cocoa API that would return a NSString in Obj-C. This means it’s not possible *in Swift* to apply NSString methods to a NSString and stay entirely within the NSString world without casting/converting. *That’s* wacky, given that String and NSString are different classes with different (though very similar) APIs. The only way to un-wack this, that I can think of right now, would be for expressions like ‘someNSString.stringByTrimmingCharactersInSet (…) as NSString’ to involve only a cheap or free conversion from String to NSString. However there is no API contract to this effect AFAIK. Therefore: 1. We need a god-like personage to step in and un-wack this for real. 2. Subject to the outcome of #1, you can approach this entirely in the NSString world, in which case I like Uli’s suggestion, applied to 'yourAttributedString.string as NSString’. You’d have to verify by performance testing that massive conversions aren’t being made. _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
