Clean way to keep all private variables in class ( private struct, pimpl idiom )

[atomic]

Hi, I would ask, how you keep private variables in the class? If there are a few then it is not a problem but now I have already over a dozen variables in class and I look for some way to do it more "clean".

Now I use private structure to storage all my private variables, for example

class CustomClass
{ 
    struct Data {
        QTableWidgetItem * hoverItem;
        QLabel label;
        QString text;
        QAction file;
        QAction save;      
        // other variables     
    };
 
public:
    CustomClass();
    ~CustomClass();
 
private:
    Data data;
};

class CustomClass
{ 
    struct Data {
        QTableWidgetItem * hoverItem;
        QLabel label;
        QString text;
        QAction file;
        QAction save;      
        // other variables     
    };

public:
    CustomClass();
    ~CustomClass();
    
private:
    Data data;
};

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I also read about pimpl Idiom
http://qt-project.org/wiki/Dpointer.

How you are doing it in daily work?
Thanks,

[Alundra]

pimpl is only really needed if you need platform-independent data or wanting to hide a lib data.
if you don't need to hide data, just stay with private data.

[Santosh Reddy]

Hi, I would ask, how you keep private variables in the class?

It will sound silly but it is the fact. You have to declare under the "private:" section in the class.

If there are a few then it is not a problem but now I have already over a dozen variables in class and I look for some way to do it more "clean".

I think you should try to have more organized code.

Now I use private structure to storage all my private variables, for example

You just pushed your "non-clean" private variables to another structure, IMO now the structure is "not-clean".

I also read about pimpl Idiom

By using private implementation, you will me moving the all the variable (non-clean) variables from *.h to *.cpp file. IMO now the *.cpp file is not clean.

How you are doing it in daily work?

I personally give attention to organizing the classes, structs by their functionalities. In a case there are more private variables (more than 15/20) then I consider that the class / struct is taking too much functionality it be better have some nested classes/struct to manage smaller functions or if any of these smaller functions are of general in nature then split the class itself. Make is just a guideline not rule to your code.

[atomic]

Maybe I wrong name this post, I thought about a large number of private variables as you say > 15.
Sometimes this "data" structure can eliminated conflict of names and you do not need create prefix to variables like _m or similar.
Thanks,

[Alundra]

Coding rules are important, and that's important to keep these rules during all the development.
For class member, keep the "m_" or just "m" front of variables.
Use "Set", "Get", "Count" and "Compute" in function's names.

[stampede]

pimpl is only really needed if you need platform-independent data or wanting to hide a lib data.

Or you want to shorten the rebuild time (change in the class internals will require to rebuild only the class.cpp file). Very useful in large projects IMHO.

[Kryzon]

Hi, I would ask, how you keep private variables in the class? If there are a few then it is not a problem but now I have already over a dozen variables in class and I look for some way to do it more "clean".

I just resort to proper naming, commenting and using whitespace to separate members into logical blocks.

class CustomClass
{
	Q_OBJECT
 
	public:
		CustomClass();
		~CustomClass();
 
	private:
		// Widgets.
 
		QTableWidget* m_mainTable;
	        QTableWidgetItem* m_hoverItem;
	        QLabel m_label;
 
		// QActions.
 
	        QAction m_fileOpen;
	        QAction m_fileSave;
		QAction m_fileClose;
 
		// Data.
 
	        QString m_text;
		QString m_lastFile;
};

class CustomClass
{
	Q_OBJECT

	public:
		CustomClass();
		~CustomClass();

	private:
		// Widgets.

		QTableWidget* m_mainTable;
	        QTableWidgetItem* m_hoverItem;
	        QLabel m_label;

		// QActions.

	        QAction m_fileOpen;
	        QAction m_fileSave;
		QAction m_fileClose;

		// Data.

	        QString m_text;
		QString m_lastFile;
};

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Do you have name conflicts right now? If you're just planning ahead to avoid it, it might be a case of you being overzealous:
http://c2.com/cgi/wiki?YouArentGonnaNeedIt

Although its not a formal source and you have to be careful with what you look at, I sometimes like to reference the source code of other Qt applications to look for stylistic choices and patterns: http://qt-apps.org/

[wysota]

For complex cases I use pimpl-like solution, for simple ones I use private members directly. I don't consider it cluttering the file. Pimpl is also fine if you want to hide the internal representation of the object when implementing a library.