Well, given that you can’t do iOS development with Smalltalk (unless you go cross-platform with Cordova/PhoneGap), you don’t have much choice but to use Objective-C/Swift.
Swift is in a whole other category of language, though. Unlike Smalltalk, Swift is a fairly big, complex language. It’s comparable to Scala, which is a real beast!
And while I’m at it, I absolutely hate Xcode. Every time I try to use Xcode, it gives me conniptions. Xcode doesn’t even come close to the elegance of Visual Studio and Android Studio (IntelliJ).