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First things first: if you’ve never touched Objective-C or Cocoa before, you need to backfill some knowledge before you jump into Enterprise iOS. There are any number of good books out there to get you started with the basic Apple development tools such as Xcode. One good place to start is Learning iPhone Programming by Alasdair Allan, also published by O’Reilly. Apple also provides a number of good resources to members of their developer community.
I’m also going to make the assumption in this book that you, the reader, are familiar with the ins and outs of Enterprise software development, including concepts such as SOAP, XML, REST, source control, continuous integration and regression, unit testing and code coverage, etc.