title: Undefined symbols for architecture x86_64 vtable
body: <p>I'm trying to do a project in <strong>Netbeans</strong> C++ for mac, when I do a simple constructor for a class named <strong>servicio</strong> the compiler shows me the following error:</p>
  
  <pre><code>"/Applications/Xcode.app/Contents/Developer/usr/bin/make" -f nbproject/Makefile-Debug.mk QMAKE= SUBPROJECTS= .build-conf
  "/Applications/Xcode.app/Contents/Developer/usr/bin/make"  -f nbproject/Makefile-Debug.mk dist/Debug/GNU-MacOSX/medicos
  mkdir -p dist/Debug/GNU-MacOSX
  g++     -o dist/Debug/GNU-MacOSX/medicos build/Debug/GNU-MacOSX/agenda.o build/Debug/GNU-MacOSX/cita.o build/Debug/GNU-MacOSX/contenedor.o build/Debug/GNU-MacOSX/doctor.o build/Debug/GNU-MacOSX/fecha.o build/Debug/GNU-MacOSX/main.o build/Debug/GNU-MacOSX/objetoBase.o build/Debug/GNU-MacOSX/paciente.o build/Debug/GNU-MacOSX/padecimiento.o build/Debug/GNU-MacOSX/servicio.o 
  Undefined symbols for architecture x86_64:
    "vtable for servicio", referenced from:
        servicio::servicio(std::__1::basic_string&lt;char, std::__1::char_traits&lt;char&gt;, std::__1::allocator&lt;char&gt; &gt;) in servicio.o
    NOTE: a missing vtable usually means the first non-inline virtual member function has no definition.
  ld: symbol(s) not found for architecture x86_64
  clang: error: linker command failed with exit code 1 (use -v to see invocation)
  make[2]: *** [dist/Debug/GNU-MacOSX/medicos] Error 1
  make[1]: *** [.build-conf] Error 2
  make: *** [.build-impl] Error 2
  </code></pre>
  
  <p>I'm not really sure what the problem might be, I'm a beginner at programming so I do not know much about this, Thanks for helping me.</p>