xcode6.0升级到xcode6.1后，程序编译报错，错误如下：这是个很常见的错误，很多项目在更换xcode版本后，都会出现类似的问题。
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)
解决方案：
Xcode升级到6.1.1 默认让所有App都通过64位编译器编译。原来在Xcode6.0的时候默认的Architectures只有（arm7,armv7s），到6.1.1默认就带上arm64的参数了。
1.把1.选中Targets—>Build Settings—>Architectures。
把build active architectures only 改为 NO。
2. 把最下面的Valid Architectures中的arm64参数删掉就可以了
或者：
双击Architectures，选择other，删除$(ARCH_STANDARD)，然后增加armv7和armv7s（写上：$(ARCHS_STANDARD_32_BIT)）。
3.clean 再build。
结果设置如下图：
目前设置完成后，问题顺利解决，大家有更好的解决方案，欢迎讨论！