Cannot Understand Event Earsffdr Cocoa-Applescript

Question

Hello Guys,
I'm trying to just write a little X-code 4 app to display it's own directory, using Cocoa-Applescript. I've created a window under MainMenu.xib, and linked it to my code in AppDelegate.applescript. My code looks something like this:
on myButtonHandler_(sender)
        set theFolder to POSIX path of (the path to current application)
        set theFile to theFolder & "/Contents/Resources/Dir.app"
        display dialog (the path to me)
        return void
    end myButtonHandler
The app builds perfectly, but when I click the button, it says:
[AppDelegate myButtonHandler:]: «script» doesn’t understand the «event earsffdr» message. (error -1708)
I have no idea what is happening there, so any help is appreciated!
P.S This code also works perfectly in Applescript Editor, but I want it to look better with a window, so this is really weird.

Answer 1

I've tried the applecation bundle thing, and my code looks like this:
    on myButtonHandler_(sender)
        set theFolder to POSIX path of (the path to current application's NSBundle's mainBundle()'s bundlePath())
        set theFile to theFolder & "/Contents/Resources/Dir.app"
        display dialog theFile
    end myButtonHandler
But now the error is:
«class ocid» id «data optr00000000E0B3660401000000» doesn’t understand the «event earsffdr» message. (error -1708)
In Applescript Editor, the code makes the error : NSBundle doesn’t understand the mainBundle message.
In addition, 'path to current application' doesen't work either, and it displays the original error.