iOS編譯報錯：objc-class-ref in AppDelegate.o之解決方案

xcode6.0升級到xcode6.1後，程式編譯報錯，錯誤如下：這是個很常見的錯誤，很多項目在更換xcode版本後，都會出現類似的問題。

Undefined symbols for architecture x86_64:

  "_OBJC_CLASS_$_QQApiInterface", referenced from:

      objc-class-ref in AppDelegate.o

  "_OBJC_CLASS_$_ShareSDK", referenced from:

      objc-class-ref in AppDelegate.o

      objc-class-ref in RecipeDetailViewController.o

      objc-class-ref in showViewController.o

      objc-class-ref in video_show.o

  "_OBJC_CLASS_$_TencentOAuth", referenced from:

      objc-class-ref in AppDelegate.o

  "_OBJC_CLASS_$_WXApi", referenced from:

      objc-class-ref in AppDelegate.o

  "_OBJC_CLASS_$_WeiboApi", referenced from:

      objc-class-ref in AppDelegate.o

  "_OBJC_CLASS_$_YXApi", 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)

解決方案：

Xcode升級到6.1.1 預設讓所有App都通過64位編譯器編譯。原來在Xcode6.0的時候預設的Architectures只有（arm7,armv7s），到6.1.1預設就帶上arm64的參數了。

1.把1.選中Targets—>Build Settings—>Architectures。

把build active architectures only 改為 NO。

2. 把最下面的Valid Architectures中的arm64參數刪掉就可以了

   或者：

雙擊Architectures，選擇other，刪除$(ARCH_STANDARD)，然後增加armv7和armv7s（寫上：$(ARCHS_STANDARD_32_BIT)）。

3.clean 再build。

結果設定如下圖：