Viadeo Twitter Google Bookmarks ! Facebook Digg del.icio.us MySpace Yahoo MyWeb Blinklist Netvouz Reddit Simpy StumbleUpon Bookmarks Windows Live Favorites 
Logo Documentation Qt ·  Page d'accueil  ·  Toutes les classes  ·  Classes principales  ·  Annotées  ·  Classes groupées  ·  Fonctions  · 

Refactoring Existing Code

[ Previous: Using Qt Main Window Classes ] [ Home ] [ Next: Replacing the View Widget ]

In the author's view, the existing code is slightly disorganized. Even though the code does work, some cleanups and reorganization can only help with readability and maintainability. The steps described below are not necessary during the migration process but are included for completeness.

Migrating Data Structures to C++

The Page data structure is an opaque data type. The real data structure is called PageRec; Page defined to be a pointer to a PageRec. In addition, we have the AllocPage() function that allocates and initializes memory for a PageRec struct.

With C++, we can do this in the constructor. We can also write a destructor which automatically frees all resources in the PageRec, instead of having to do it in several different places.

The PageRec struct declaration is removed from page.h. We declare a Page struct with the same data members as PageRec, a constructor and a destructor. 



 The existing pages, currentPage and maxpages global variables
are removed from the source files.  We replace them with extern
declarations in page.h.

 


 The global variable instantiations are placed in todo.cpp.

 Each source file contains function declarations that deal with the
global Page related variables.  We remove these declarations from
the source files and declare them once in the page.h header file.

 


 Now that Page has a constructor, we remove the AllocPage()
function.  It is no longer needed.  The calls to AllocPage() are
replaced with 'new Page()' in the NewPage(), DeletePage()
and ReadDB() functions.  We also replace the code to deallocate
pages with delete pages[X], where X is the appropriate index
value.  This is done in the ReadDB and DeletePage() functions.

 Code that accesses the global pages variable does not need to be
modified since the data members of the Page struct did not change.
The existing code will continue to work.

 The OptionsRec struct declared in page.h is also updated,
following the same pattern as the Page struct above.

 


 The global variable instantiation is also placed in todo.cpp.

 Code that accesses the global options variable does not need to be
modified since the data members of the Options struct did not
change.  The existing code will continue to work.

 
 Using new and delete



 The destructors of the Page and Options structs use delete
instead of XtFree() to deallocate all char* members.  This is a
necessary change since we are migrating away from Xt/Motif.  We need
to fix existing code that modifies the Page struct members to use
new and delete ( instead of XtMalloc(), XtNewString() and
XtFree() ).

 The PageChange() function in todo.cpp simply saves the contents
and cursor position of current page before calling SetPage().  We
use new and delete when modifying members of the Page struct.

 




 When storing the context of the XmText widget, we use qstrdup()
to make a copy of the string returned by the XmTextGetString()
function.

 


 The ReadDB() function in io.cpp needs similar changes.  We
replace all use of XtMalloc() and XtNewString() with new and
qstrdup(), respectively.

 This needs to be done just after opening the file.

 




 ... when starting a new page ...

 
    ...


 



 ... and when reading in the label and tab texts/

 
    ...


 

    ...


 

    ...


 



 The ReadDB() function uses XtRealloc() to expand the data
storage buffer.  Unfortunately, C++ does not provide a way to
reallocate an existing block of data, so we have to do this ourselves.

 


 There is also one occurence in ReadDB() where we call XtMalloc()
with an argument of 2.  This was done when a file could not be read.
Creating an empty string is not necessary, so we remove this code
instead of using new.

 


 The SaveDB() function in io.cpp also needs these changes.  We
change one occurence of XtFree() to delete.

 


 Finally, We need to replace two occurences of XtNewString() in the main() function in todo.cpp.

 




 
 Moving Existing Code



 The rest of the refactoring process involves moving existing code into
new places.  Currently, each function in the mainwindow.ui.h file
simply calls the old callback handlers present in the other files.
Instead of calling the old callback functions, the implementations are
moved accordingly.

 


 Function             Original File  Moved to Function 

    New()             todo.cpp    MainWindow::fileNew()

    Open()            todo.cpp    MainWindow::fileOpen()

    SaveIt()          actions.cpp MainWindow::fileSave()

    Save()            todo.cpp    MainWindow::fileSaveAs()

    ShowPrintDialog() todo.cpp    MainWindow::filePrint()

    EditPage()        actions.cpp MainWindow::selProperties()

    NewPage()         actions.cpp MainWindow::selNewPage()

    DeletePage()      actions.cpp MainWindow::selDeletePage()



 The Print() callback function is still used by the Print
dialog, so we move it into mainwindow.ui.h and make it static.

 Previously, the Open(), Save(), EditPage() and DeletePage()
functions created dialogs with client_data as the parent argument.
Since we have moved the code directly into the Main Window
implementation, we create these dialogs with this as the parent
argument.

 The PageChange() callback function is moved from actions.cpp
to todo.cpp and made static since it is not used anywhere else.

 Earlier modifications to actions.cpp caused the Trim() function
to become redundant, so we remove it.

 The MIN() and MAX() macros in todo.cpp are redundant.  Qt
provides the QMIN() and QMAX() macros which we will use.

 Earlier modifications caused the fallback_resources array to become
redundant, so we remove it. 

 In the near future, our program will not use Motif any more, and we
will no longer need to use QMotif.  To prepare for this, we remove the
resources and optionDesc arrays and create the QMotif instance
with just the APP_CLASS argument.

 The #include statements in the source files are mostly incorrect
due to the refactoring changes.  Many of the #include statements
are no longer needed.  The #include statements from each file are
listed below, instead of describing which includes are removed and
added to each file.  

 Includes for actions.cpp:

 




 Includes for io.cpp:

 




 Includes for todo.cpp:

 




 Includes for mainwindow.ui.h:

 




 [ Previous: Using Qt Main Window Classes ]
[ Home ]
[ Next: Replacing the View Widget ]

 


					
			
			
				       




Publicité


			

Best Of


 
	




	
Actualités les plus lues

	
	
		
Semaine

		
Mois

		
Année

	

	

		
		

			
    

  1. 
	« Quelque chose ne va vraiment pas avec les développeurs "modernes" », un développeur à "l'ancienne" critique la multiplication des bibliothèques
		44
	 
    2. 

  2. 
	Microsoft ouvre aux autres compilateurs C++ AMP, la spécification pour la conception d'applications parallèles C++ utilisant le GPU
		22
	 
    3. 

  3. 
	Les développeurs ignorent-ils trop les failles découvertes dans leur code ? Prenez-vous en compte les remarques des autres ?
		17
	 
    4. 

  4. 
	RIM : « 13 % des développeurs ont gagné plus de 100 000 $ sur l'AppWord », Qt et open-source au menu du BlackBerry DevCon Europe
		0
	 
    5. 

  5. 
	BlackBerry 10 : premières images du prochain OS de RIM qui devrait intégrer des widgets et des tuiles inspirées de Windows Phone
		0
	 
    6. 

  6. 
	Quelles nouveautés de C++11 Visual C++ doit-il rapidement intégrer ? Donnez-nous votre avis
		10
	 
    7. 

  7. 
	Adieu qmake, bienvenue qbs : Qt Building Suite, un outil déclaratif et extensible pour la compilation de projets Qt
		17
	 
    8. 


	

Page suivante

		

		
	

		
   







Le blog Digia au hasard



Logo

Déploiement d'applications Qt Commercial sur les tablettes Windows 8


Le blog Digia est l'endroit privilégié pour la communication sur l'édition commerciale de Qt, où des réponses publiques sont apportées aux questions les plus posées au support. Lire l'article.





Communauté




Ressources




Liens utiles




Contact


    

  • Vous souhaitez rejoindre la rédaction ou proposer un tutoriel, une traduction, une question... ? Postez dans le forum Contribuez ou contactez-nous par MP ou par email (voir en bas de page).
    • 




Qt dans le magazine




 

					
		

	




	

		

			
				Cette page est une traduction d'une page de la documentation de Qt, écrite par Nokia Corporation and/or its subsidiary(-ies). Les éventuels problèmes résultant d'une mauvaise traduction ne sont pas imputables à Nokia. 
			
			
				Qt 3.3
			
			
		

		

			
				Copyright © 2012 Developpez LLC. Tous droits réservés Developpez LLC. Aucune reproduction, même partielle, ne peut être faite de ce site et de l'ensemble de son contenu : textes, documents et images sans l'autorisation expresse de Developpez LLC. Sinon, vous encourez selon la loi jusqu'à 3 ans de prison et jusqu'à 300 000 E de dommages et intérêts. Cette page est déposée à la SACD.
			
			
		

		

			
				Vous avez déniché une erreur ? Un bug ? Une redirection cassée ? Ou tout autre problème, quel qu'il soit ? Ou bien vous désirez participer à ce projet de traduction ? N'hésitez pas à nous contacter
 ou par MP ! 
			
			
		

	


							
							

						

					

				
				

				
	
	
	



	
 


	
 


	

	

		

			Developpez.com
			
Nous contacter

			
Participez

			
Informations légales

		

		
 

		

			Services
			
Forum Qt

			
Blogs

			
Hébergement

		

		
 

		

			Partenaires
			
Hébergement Web