title: Replace AppDelegate.h and AppDelegate.m to AppDelegate.swift
body: <p>I just have a Objective-C project and I want to use AppDelegate to access to my xcdatamodel, but when I add <code>AppDelegate.swift</code> to my project it show me a compile problem, it is error because it doesn't know what AppDelegate use and what is the main. Then I tried to delete <code>AppDelegate.h</code> and <code>AppDelegate.m</code> and add <code>AppDelegate.swift</code>, but it also doesn't work and still has compile errors.
  How I can add <code>AppDelegate.swift</code> to it?</p>