Undefined symbols for architecture x86_64: （ linker command failed with exit code 1）

当出现  linker command failed with exit code 1 (use -v to see invocation) 的错误总结，具体内容如下：

Undefined symbols for architecture x86_64:

"_OBJC_CLASS_$_AppDelegate", referenced from:

objc-class-ref in main.o

ld: symbol(s) not found for architecture x86_64

clang: error: linker command failed with exit code 1 (use -v to see invocation)

解决方法：

找到你的工程，BuildPhases，Compile Source，然后看上图中提示找不到那个类名，此处是

AppDelegate，所以在Compile Source一栏里点击左下角的“+”号，手动添加AppDelegate.m，再次运行程序，完美解决！

至于出现 Undefined symbols for architecture armv7: 这样的出错提示，可以参考这个链接解决http://blog.csdn.net/hengshujiyi/article/details/21182813