linker command failed with exit code 1 (use -v to see invocation) and Undefined symbols for architecture

Question

i have problem, and i can't figure out why..

Undefined symbols for architecture x86_64:
  "_OBJC_CLASS_$_QButtonElement", referenced from:
      objc-class-ref in AppDelegate.o
  "_OBJC_CLASS_$_QEntryElement", referenced from:
      objc-class-ref in AppDelegate.o
  "_OBJC_CLASS_$_QRootElement", referenced from:
      objc-class-ref in AppDelegate.o
  "_OBJC_CLASS_$_QSection", referenced from:
      objc-class-ref in AppDelegate.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Answer 1

I figured it out, i still used the QButtonElement in code even if i already deleted the class..