implicit declaration of function 'NSlog' is

      invalid in C99 [-Wimplicit-function-declaration]

    NSlog(@"hahaha");

    ^

1 warning generated.

Undefined symbols for architecture x86_64:

  "_NSlog", referenced from:

      _main in 08-第二个OC的类-675h5l.o

  "___CFConstantStringClassReference", referenced from:

      CFString in 08-第二个OC的类-675h5l.o

ld: symbol(s) not found for architecture x86_64

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

Undefined symbols for architecture x86_64:

  "_NSLog", referenced from:

      -[Person walk] in 08-第二个OC的类-k6D7Eq.o

      -[Person eat] in 08-第二个OC的类-k6D7Eq.o

  "_OBJC_CLASS_$_NSObject", referenced from:

      _OBJC_CLASS_$_Person in 08-第二个OC的类-k6D7Eq.o

  "_OBJC_METACLASS_$_NSObject", referenced from:

      _OBJC_METACLASS_$_Person in 08-第二个OC的类-k6D7Eq.o

  "___CFConstantStringClassReference", referenced from:

      CFString in 08-第二个OC的类-k6D7Eq.o

      CFString in 08-第二个OC的类-k6D7Eq.o

  "__objc_empty_cache", referenced from:

      _OBJC_METACLASS_$_Person in 08-第二个OC的类-k6D7Eq.o

      _OBJC_CLASS_$_Person in 08-第二个OC的类-k6D7Eq.o

  "__objc_empty_vtable", referenced from:

      _OBJC_METACLASS_$_Person in 08-第二个OC的类-k6D7Eq.o

      _OBJC_CLASS_$_Person in 08-第二个OC的类-k6D7Eq.o

  "_objc_msgSend", referenced from:

      _main in 08-第二个OC的类-k6D7Eq.o

ld: symbol(s) not found for architecture x86_64

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

是不是编译的时候 没加-framework Foundation 啊