Question: When trying to run my project I get this error and I don´t know what it means : 

> 
> \_OBJC\_CLASS\_$\_MyWindowController", referenced from:
>  objc-class-ref in AppDelegate.  
> 
>  ld: symbol(s) not found for architecture x86\_64
>  clang: error: linker command failed with exit code 1 (use -v to see invocation)
> 
> 
> 

What does it mean and how can I get rid of it?

Any ideas?

Answer: 
Select the application target, go to the **Build Phases** tab and make sure **MyWindowController.m** is in **Compile Sources**, otherwise add it.

Also, if you use a **xib** file associated with it, make sure it is in **Copy Bundle Resources**.
Check to see if the framework that your MyWindowController object is based on has been added to your project.

Good luck!