The nearest thing to VB6 for the Mac is "Xojo", it used to be called "Real basic", but they decided to rebrand themselves in order to loose the "Basic" label.
It's language and syntax is similar to VB6, and it's IDE is similar to "Visual Studio".
http://www.xojo.com
As of now "Xojo" compiles for Mac OSX, Windows, and Linux, although they have announced the release of their iOS framework for early 2015, but you will have to watch their web page space for updates on that.
I've used it on occasions in the past, but their annual licence fees are expensive, and they seem to be in a constant state of debugging and update work, so their package is always being updated, requiring frequent downloaded updates to your system, and also frequent licence renewals in order to be able to update your system.
Personaly if your serious about developing iOS apps now, I would learn Objective-C and Swift, it's the only real native solution for iOS development, and especially given the fact that the Cocoa Touch framework will be redeveloped over the next few years away from Objective-C, and to be probably more Swift friendly.
Something that will probably cause more update problems for the hard working team at Xojo, and always leave them playing catch up.
Hope this helps.
Regards Mark