🚀 go-pugleaf

On Sun, 20 Jan 2002 23:19:36 -0000, "Max Coppin"
<maxcoppin@btinternet.com> wrote:

>Hi,
>I'm trying to convert one of my C++ programs to use the singleton pattern.
>I've got the Design Patterns book by Gamma et all and am just trying to copy
>a piece of code from that.  The code is below, as is the error i get.  My
>first question is where should these pieces of code go?  I presume that the
>definition goes in a .h and the implementation in a .cpp and then call in
>from main.cpp or whatever.  Is this correct, can anyone help?
>
>maxcoppin@btinternet.com
>

Try adding the line below:
>
>class MazeFactory
>{
>public:
> static MazeFactory* Instance();
>protected:
> MazeFactory();
>
>private:
> static MazeFactory* _instance;
>};
>
//Add this line
MazeFactory::MazeFactory() {}

>
>MazeFactory* MazeFactory::_instance=0;
>
>MazeFactory* MazeFactory::Instance()
>{
> if(_instance == 0)
> {
>  _instance= new MazeFactory;
> }
> return _instance;
>}
>
>
>ERROR MESSAGE :-
>
>--------------------Configuration: ProjTemplate - Win32
>Release--------------------
>Compiling...
>main.cpp
>test.cpp
>Generating Code...
>Linking...
>test.obj : error LNK2001: unresolved external symbol "protected: __thiscall
>MazeFactory::MazeFactory(void)" (??0MazeFactory@@IAE@XZ)
>Release/ProjTemplate.exe : fatal error LNK1120: 1 unresolved externals
>Error executing link.exe.
>
>ProjTemplate.exe - 2 error(s), 0 warning(s)
>
>

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