MVC and dialogs

[Randall Twede]

i am refactoring an old project to fit a MVC framework. in the original i just displayed the dialogs from action Performed. the framework i am forcing it into uses showXXXdialog() methods in View, and calls them from actionPerformed(). ok this seems alright, but!!! the program i am refactoring gets input from some dialogs.the code will show what i am talking about.

actionPerformed() from the original program:

    public void actionPerformed(ActionEvent e)
    {
        String animal = new String();
        String question = new String();
        
        if(((JButton)e.getSource()).getText().equals("Quit"))
        {
            tree.saveKnowledgeBase();
            System.exit(0);
        }
        else if(((JButton)e.getSource()).getText().equals("Begin"))
        {
            yes.setText("Yes");
            no.setText("No");
            message.setText((String)current.getElement());
        }
        else if(message.getText().endsWith("Would you like to play again?"))
        {
            if(e.getSource() == yes)
            {
                yes.setText("Begin");
                no.setText("Quit");
                message.setText(instructions);
                current = tree.root;
            }
            else
            {
                tree.saveKnowledgeBase();
                System.exit(0);
            }
        }
        else
        {
            if(e.getSource() == yes)
            {
                if(current.getRightChild() != null)
                {
                    current = current.getRightChild();
                    message.setText((String)current.getElement());
                }
                else
                {
                    message.setText("I guessed it! Would you like to play again?");
                }
            }
            else
            {
                if(current.getLeftChild() != null)
                {
                    current = current.getLeftChild();
                    message.setText((String)current.getElement());
                }
                else    // get new knowledge
                {
                    animal = "Is it a " + (String)JOptionPane.showInputDialog(null, 
                            "I give up, what is the animal? just the name in lower case please.") + "?";
                    question = (String)JOptionPane.showInputDialog(null, 
                            "Please provide a question that, if answered yes, means you are thinking of a " + 
                             animal + "instead of a " + ((String)current.getElement()).substring(8));
                    current.setLeftChild(new BinaryTreeNode(current.getElement()));
                    current.setRightChild(new BinaryTreeNode(animal));
                    current.setElement(question);
                    message.setText("Thank you! Would you like to play again?");
                }
            }
        }
    }
   
    // create and display an instance of TwentyQuestions
    public static void main(String args[])
    {
        TwentyQuestions test = new TwentyQuestions();
        test.center(test, 150, 250);
        test.setVisible(true);
        test.setDefaultCloseOperation(EXIT_ON_CLOSE );
    }

what i have now:

from TopController:

	public void actionPerformed( ActionEvent e )
	{
	    String strID = e.getActionCommand();

	    if( strID.equals( Constants.CREATE ) )
	    {
		if( view.showCreateDialog() )
		model.create();
	    }
	    if( strID.equals( Constants.QUIT ) )
	    {
		if( view.showQuitDialog() )
		{
            	    model.save();
            	    System.exit(0);
		}
		view.requestFocus();
	    }
	    else if( strID.equals( Constants.ABOUT ) )
	    {
		view.showAboutDlg();
		view.requestFocus();
	    }
            else if(strID.equals(Constants.BEGIN))
            {
		view.changeButtons();
            	view.setMessage(model.getMessage(Constants.BEGIN));
            }
        else if(view.getMessage().endsWith("Would you like to play again?"))
        {
            if(strID.equals(Constants.YES))
            {
                view.changeButtons();
                view.setMessage(Constants.INSTRUCTIONS);
                model.reset();
            }
            else
            {
                model.save();
                System.exit(0);
            }
        }
	else if(strID.equals(Constants.YES))
	{
	    view.setMessage(model.getMessage(Constants.YES));
	}
	else if(strID.equals(Constants.NO))
	    view.setMessage(model.getMessage(Constants.NO));
	{
	}		
	} // End actionPerformed

from Model:

    public String getMessage(String button)
    {
	String message;

	if(button.equals("Begin"))
	{
	    message = (String)current.getElement();
	}
	else if(button.equals("YES"))
	{
            if(current.getRightChild() != null)
            {
                current = current.getRightChild();
                message = (String)current.getElement();
            }
            else
            {
                message = "I guessed it! Would you like to play again?";
            }
	}
	else	//button.equals("NO")
	{
            if(current.getLeftChild() != null)
            {
                current = current.getLeftChild();
                message = (String)current.getElement();
            }
            else    // get new knowledge
            {
		String input = (String)JOptionPane.showInputDialog(null, 
                        "I give up, what is the animal? just the name in lower case please.");
                String animal = "Is it a " + input + "?";
                String question = (String)JOptionPane.showInputDialog(null, 
                        "Please provide a question that, if answered yes, means you are thinking of a " + 
                        input + " instead of a " + ((String)current.getElement()).substring(8));
                current.setLeftChild(new BinaryTreeNode(current.getElement()));
                current.setRightChild(new BinaryTreeNode(animal));
                current.setElement(question);
                message = "Thank you! Would you like to play again?";
	    }
	}
	return message;
    }	// end getMessage()

first of all it seems kind of silly to call a View method from Controller just to display a dialog.
what is worse is now i have to display a dialog from Model. importing View into Model just to display a dialog seems ridiculous to me.

i don't know why the code posted so poorly, hope you can still read it.

[Edit - fixed code tags - MB]

[Jimmy Clark]

Why did you decide to change the code to implement a Model-View-Controller design pattern? For your application will there be any benefits?

[Randall Twede]

no, it is just to help me re-learn the pattern/framework. actually i see little benefit gained since it is a pretty small project.

[Jimmy Clark]

Sounds good. Keep in mind that there are Model-View-Controller-based "frameworks" which are implementing a portion of the Model-View-Controller "object-oriented design pattern." Apache Struts is a good example of a MVC-based framework which is based on the MVC design pattern. Struts enables developers to easily build application Controllers and provides a robust Java Server Page Tag library for creating a HTML-based View. Sometimes individuals miss the fact that a MVC framework is simply a partial implementation of the corresponding OO design pattern. When the framework creators use the "MVC" acronym to describe their work, things get more confusing than they have to be. At its core, MVC is a design concept only.

That said. The other relevant point that you may be close to understanding it that object-oriented design patterns are most beneficial for "big" things, not "small" things. For large applications with teams of developers, not a single programmer. Design patterns are communication tools which enable individuals to discuss complex topics in a simplified and abstract way.