Depending on complexity of your app and the level of polish, it might take a while.
I mean, you can make an app in a day if you follow a tutorial, but if you want to enjoy the language and what you're doing, then you'll have to put in the effort.
Objective-C can probably be avoided, but will help a lot in some cases - especially when interfacing with libraries written in ObjC or C++. So you might want to learn them in parallel, or at least spend a bit of time understanding the semantics of the language, memory management, concurrency, etc.
Oh and native iOS is different from native macOS, some APIs are not compatible, but you can reuse quite a bit of utility-level functions related to your app (since it's the same language).
I enjoyed learning ObjC and Swift and writing apps for iOS, the only issue I have with this platform is that it's too crowded for (new) solo devs.
If you don't care about that as much, then by all means go ahead, you will love it.
I mean, you can make an app in a day if you follow a tutorial, but if you want to enjoy the language and what you're doing, then you'll have to put in the effort.
Objective-C can probably be avoided, but will help a lot in some cases - especially when interfacing with libraries written in ObjC or C++. So you might want to learn them in parallel, or at least spend a bit of time understanding the semantics of the language, memory management, concurrency, etc.
Oh and native iOS is different from native macOS, some APIs are not compatible, but you can reuse quite a bit of utility-level functions related to your app (since it's the same language).
I enjoyed learning ObjC and Swift and writing apps for iOS, the only issue I have with this platform is that it's too crowded for (new) solo devs.
If you don't care about that as much, then by all means go ahead, you will love it.