You wouldn't by any change be taking on developing apps for iOS -- the iPhone, iPad? I'm asking because I've personally only heard of Objective C being used for iOS apps.  This is important, because if are then you [***must have*** a  Macintosh][1].

If I'm wrong, ignore my answer and carry on.

Look, my original answer was deleted because it wasn't pointing a specific product. I understand those are the rules of this forum, but if my assumptions are correct, them the information provided in my answer is vital, since not buying a Macintosh (like the accepted answer recommends) will only lead to wasted money! I'm not a Mac person, but here, because rules, is a random [specific product][2] that'll actually let you compile and run Objective C as you required.  You want at least 8GB of RAM.

On a side note: You may be interested in knowing that all iOS developers (that I know of!) are moving away from Objective C and switching to the Swift programming language.


  [1]: https://stackoverflow.com/a/9570529/2412477%20%22See%20for%20yourself%22.

  [2]: http://www.ebay.com/itm/Apple-Macbook-Air-A1466-13-i5-5250U-1-6-GHz-8GB-128GB-SSD-Early-2015-/282515650467?hash=item41c73eb7a3:g:WwsAAOSwKflZOW03