Quick question regarding abstract classes and DLLs

[durbrak]

Hello,
I have a rather simple question which I can't solve on my own because I'm still a rookie
Anyway, I have my main application (main.exe) and a module.dll. My application has an AbstractModule class for custom modules and the module.dll uses this.

AbstractModule.h

//.h
class AbstractModule
{
public:
    virtual QString name() const = 0;
    bool isSomething() const;
};
 
//.cpp
bool AbstractModule::isSomething()
{
    return true;
}

//.h
class AbstractModule
{
public:
    virtual QString name() const = 0;
    bool isSomething() const;
};

//.cpp
bool AbstractModule::isSomething()
{
    return true;
}

To copy to clipboard, switch view to plain text mode 

Now I create a separate module dll for the first module ("module.dll") and it uses the "abstractmodule.h":

//.h
#include <abstractmodule.h>
class Module : public AbstractModule
{
public:
    Module();
 
    QString name() const;
};
 
//.cpp
Module::Module()
{
    bool isIt = this->isSomething(); //Link error (LNK2019)
}
QString Module::name() const
{
    return "Test";
}

//.h
#include <abstractmodule.h>
class Module : public AbstractModule
{
public:
    Module();

    QString name() const;
};

//.cpp
Module::Module()
{
    bool isIt = this->isSomething(); //Link error (LNK2019)
}
QString Module::name() const
{
    return "Test";
}

To copy to clipboard, switch view to plain text mode 

In Visual Studio I set the "module.dll"-project to be dependent on the "main.exe"-project.
But when I try to compile the solution I get a link error:

error LNK2019: unresolved external symbol [...]

I guess it has somehow to do with the fact that the definition of AbstractModule::isSomething() is in the .exe?
I'm sorry, but I'm totally new to this whole dll stuff
Thank you for your help.

[wysota]

If the abstract module has at least one method actually implemented, you have to add the definition to the dll as well, you can't make a dll depend on an exe (only the other way round).

Hint: You can define some methods in the header file, so you don't have to add any cpp files to your library.