A question about backend of creating the app with Xcode

Question

Hi,
I'm a new iphone developer who just started to learn how to create iphone apps.
I just started to learn about view-based applications.
When I select view-based applications, XCode will automatically generate some files for me.
For example, if a create a new project called "A", XCode will generate files like "AViewController.m", "AAppDelegate.m", and "main.m".
but I don't see anywhere in those files where it's actually creating the instance of "AViewController" or "AAppDelegate".
So at where and at which file are the instances of "AViewController" and "AAppDelegate" created?
Also where is the instance of the main application created?(not A.app if you know what I mean)

Answer 1

I hope I can add to the correct answer posted by J D McIninch since the solution to this thread might provide a good example of how xib objects work--i.e. what I tried to explain in your [previous thread|http://discussions.apple.com/message.jspa?messageID=11479911#11479911].
Daviiidddd wrote:
So at where and at which file are the instances of "AViewController" and "AAppDelegate" created?
Open MainWindow.xib and make sure the xib window is visible by selecting Document from the Windows menu. You should see a solid orange cube labeled "A App Delegate", and a circular icon labeled "A View Controller". These icons represent IB objects. The objects are described by xml elements in the xib file, and that xml will direct the system to create the real objects in memory when the xib is loaded. While it's not technically correct to say the real objects are "created by IB", we can say that the specification for the real objects is built in IB. In other words, the xib file which results from an IB editing session contains a tree of specifications which will be used to create real objects at runtime.
Btw, to graphically see the tree of xib objects (the "view hierarchy", find the +View Mode+ switch in the upper-left corner of the xib window. Select the Center position of that switch so the window displays a two column table with a tree of small icons to the left. This is the xib view I recommend for all your work.
Also where is the instance of the main application created?(not A.app if you know what I mean)
The Application object is created by the [UIApplicationMain()|http://developer.apple.com/iPhone/library/documentation/UI Kit/Reference/UIKitFunctionReference/Reference/reference.html#//apple_ref/doc/ui d/TP40006894-CH3-SW7] function called by main() in main.m. The MainWindow.xib is then loaded, and the Application object is given ownership of that xib. This means that the File's Owner proxy object represents the real Application object, so all connections to File's Owner become connections to the real Application object.
Note that the File's Owner cube is transparent. This is IB's way of denoting a proxy object. The First Responder is actually a proxy of a different kind, but let's not go there now.
\- Ray