I'd recommend going on stacksocial.com and buying the complete iOS 8 course. Once you get that, you'll notice that you get the iOS 7 course as well. I would recommend starting with that one first in order to learn objective C. Only once you have completely finished that would I move on to Swift.
I am personally nearly finished with the iOS 7 course...and I started back in May, so it's not a month long course for most by any means. personally, I also decided to subscribe to Lynda.com because they have a few good courses on things like Core Data with Simon Allardice, which I think is a very useful skill to know in and of itself. Something like Core Data can be almost impossibly difficult to understand at first, since every major concept of core data is completely dependent on every other part, so it can be hard to grasp at first. But Simon Allardice explained it well enough that I can now pretty much do anything in core data.
Books are also great. I find that I can learn just as quickly from books, but I think the video courses I've mentioned are better for some people who have never done any coding before so you can see how they move around xcode and see some tricks you could never have learned from a book. When I have a question about the actual language I mainly use Programming in Objective-C by Stephen Kochan.
It's super fun even as just a hobby. Learning iOS development has been extremely rewarding for me, it's fun just to think up new ways of doing things. Even if they've already been done by others, creating something new without anyone else's help or reference is very fun.