title: Error after creation of core data files
body: <p>I have started adding core data to my application. I created the entity with name Assets and defined its four attributes and then created Asset.h and Asset.m file for NSManagedObject. Now I am getting the following error while before that my application was working fine</p>
  
  <pre><code>Ld /Users/Omer/Library/Developer/Xcode/DerivedData/LoginTest-enoqygjnncuapjescysdafbighag/Build/Products/Debug-iphonesimulator/LoginTest.app/LoginTest normal i386
  cd /Users/Omer/Desktop/Docs/LoginTest
  setenv MACOSX_DEPLOYMENT_TARGET 10.6
  setenv PATH "/Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin:/Developer/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin"
  /Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin/clang -arch i386 -isysroot /Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator5.0.sdk -L/Users/Omer/Library/Developer/Xcode/DerivedData/LoginTest-enoqygjnncuapjescysdafbighag/Build/Products/Debug-iphonesimulator -L/Users/Omer/Desktop/Docs/LoginTest/ZBarSDK -F/Users/Omer/Library/Developer/Xcode/DerivedData/LoginTest-enoqygjnncuapjescysdafbighag/Build/Products/Debug-iphonesimulator -filelist /Users/Omer/Library/Developer/Xcode/DerivedData/LoginTest-enoqygjnncuapjescysdafbighag/Build/Intermediates/LoginTest.build/Debug-iphonesimulator/LoginTest.build/Objects-normal/i386/LoginTest.LinkFileList -mmacosx-version-min=10.6 -Xlinker -objc_abi_version -Xlinker 2 -Xlinker -no_implicit_dylibs -D__IPHONE_OS_VERSION_MIN_REQUIRED=50000 -liconv -framework QuartzCore -framework CoreVideo -framework CoreMedia -framework AVFoundation -framework MapKit -framework CoreLocation -lz -framework CoreGraphics -framework MobileCoreServices -framework SystemConfiguration -framework CFNetwork -framework Foundation -framework UIKit -lzbar -o /Users/Omer/Library/Developer/Xcode/DerivedData/LoginTest-enoqygjnncuapjescysdafbighag/Build/Products/Debug-iphonesimulator/LoginTest.app/LoginTest
  
  
  Undefined symbols for architecture i386:
  
  
   "_OBJC_METACLASS_$_NSManagedObject", referenced from:
    _OBJC_METACLASS_$_Asset in Asset.o
  
  
   "_OBJC_CLASS_$_NSManagedObject", referenced from:
    _OBJC_CLASS_$_Asset in Asset.o
  ld: symbol(s) not found for architecture i386
  clang: error: linker command failed with exit code 1 (use -v to see invocation)
  </code></pre>