Views is not connected with File's Owner in cocoa

I am new in objective-c.I am making controls like calculator.After double click on calc.xib file i am getting 3 pops i designed some control and wanting to connect with "File's Owner" with the ControlKey(a strength blue line) in Mac but unfortunate th开发者_开发技巧is is not being connect to "File's Owner".What is wrong with the code.

If your nib file is MainMenu.nib, then it is not to the File's Owner, which is an object of type NSApplication in that case, that you should connect your controls.

Either you define a controller (any object derived from NSObject) or you can use the AppDelegate.