Including a self-made library into another project

[high_flyer]

You are mixing specialization and general template.
For specializazoin you need the following syntax:

template<>
MyLibrary::MyLibrary<quint32>(qint32 qiX, qint32 qiY, qint32 qiZ)
{...
}

template<>
MyLibrary::MyLibrary<quint32>(qint32 qiX, qint32 qiY, qint32 qiZ)
{...
}

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Or a general template:

template<class T>
MyLibrary::MyLibrary(T qiX, T qiY, T qiZ)
{...
}

template<class T>
MyLibrary::MyLibrary(T qiX, T qiY, T qiZ)
{...
}

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Ah and:

This is the implementation in my .cpp file

templates are implemented in headers, not in *.cpp files.
Or more correctly said:
The implementation (definition) of a template class or function must be in the same file as its declaration, and this is usually done in a header.
Read more abut how to create and use templates in c++.

[jepessen]

I don' use T for arguments of constructor. It defines the type of a private attribute of my class, that's used inside my constructor. qiX,Y,Z are indexes to access to a (T m_xGrid[][][]) structure inside my class.

template<class T>
MyLibrary<T>::MyLibrary(qint32 qiX, qint32 qiY, qint32 qiZ)
{
 
    // Testing values to be greater or equal to zero.
    if (qiX < 0)
    {
        qDebug() << "MyLibrary<T>::MyLibrary: qiX = " << " is less than zero."
                 << " Setting X value to zero.";
        m_qiX = 0;
 
    }
    else
    {
        m_qiX = qiX;
    }
 
    // etc etc etc...
 
    // Example of use of T
    T xValue;
    xValue = m_xGrid[1][1][1];
 
}

template<class T>
MyLibrary<T>::MyLibrary(qint32 qiX, qint32 qiY, qint32 qiZ)
{

    // Testing values to be greater or equal to zero.
    if (qiX < 0)
    {
        qDebug() << "MyLibrary<T>::MyLibrary: qiX = " << " is less than zero."
                 << " Setting X value to zero.";
        m_qiX = 0;

    }
    else
    {
        m_qiX = qiX;
    }

    // etc etc etc...

    // Example of use of T
    T xValue;
    xValue = m_xGrid[1][1][1];

}

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[high_flyer]

It doesn't matter.
Your syntax is wrong and your implementation is in the wrong place.
Read well what I wrote, and google to some template tutorials.

[jepessen]

Ok, sorry... I'm reading something more about templates. Thanks for your reply.
Regards.

[SixDegrees]

Also, your application project file doesn't look right. 'LIBS += -L../../bin/libMyLibrary.so' just adds the directory to the linker search path; you need to add '-lMyLibrary' to it. The 'undefined reference' error indicates that the linker can't find your library.

But note that whatever else may be in your library, templated classes will not appear. Templates aren't code, and aren't compiled into libraries; templates are...templates that tell the compiler how to generate code when an actual instantiation of a template class occurs, so unless your library creates an instance of a template class there is nothing in it that's template related. The only place the template is defined is in the header, which is roped in at compile time.

This is all somewhat oversimplified.

[jepessen]

Thanks. Just to know, If I can't export a template with a library, how can works Qt container like, for example, QVector? Because in that case I simply include the qvector header and I can use the template. How can I do something similiar?

[SixDegrees]

You include all of your implementation in your header file so there's nothing to compile and nothing to build into a link library.

[stampede]

If I can't export a template with a library

You can deploy a header containing the template definition with other headers in library, I don't see a problem here.
Or do you mean you want to have a template code in .so file somehow ? In that case I'd suggest you read more about templates.
If this library is nothing more than a template, then you don't need any .so files, no linking to the library is required, because there is nothing to link to. All needed code will be generated in case of template instantiation.
So in fact using this library means including the header and creating an instance of template class (or method).

[jepessen]

Thanks, I've also read something about that. It's the first time that I use it for a serious project, so before I'd never noticed template differences from normal classes because I've used them always in the same project...

I have a lot to learn :-)

Thanks to anyone.