编译C多个文件时出错

Question

我正在使用

1. 的main.cpp
2. FileSystem Class - 包含2个目录（root和current）
3. 目录类 - 继承自BaseFile
4. 文件类 - 继承自BaseFile

我尝试创建一个新目录并将其设置为root。 我的构造函数是：

BaseFile::BaseFile() {
name = "default";
}
Directory::Directory() {
    parent = nullptr;
    cout << "Directory: Default Constructor" << endl;
}

尝试使用FileSystem::FileSystem() { root = new Directory(); }

时

我收到编译错误说：

    /Applications/CLion.app/Contents/bin/cmake/bin/cmake --build /Users/adammorad/ver1/cmake-build-debug --target ver1 -- -j 2
Scanning dependencies of target ver1
[ 33%] Building CXX object CMakeFiles/ver1.dir/FileSystem.cpp.o
[ 66%] Linking CXX executable ver1
Undefined symbols for architecture x86_64:
  "Directory::Directory()", referenced from:
      FileSystem::FileSystem() in FileSystem.cpp.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[3]: *** [ver1] Error 1
make[2]: *** [CMakeFiles/ver1.dir/all] Error 2
make[1]: *** [CMakeFiles/ver1.dir/rule] Error 2
make: *** [ver1] Error 2