Developing Ruby QT Applications using QT Designer and Ruby on Ubuntu

These instructions are tested with Ubuntu Jaunty Jackalope 9.04 . We will create a simple application to display a list of items (pieces of text) and move them up and down. Ground breaking in the extreme!

Install the appropriate packages

From a command line terminal run

sudo aptitude install libkorundum4-ruby1.8
sudo aptitude qt4-designer
sudo aptitude libqt4-ruby1.8-dev
sudo aptitude install libqt4-ruby1.8-examples
sudo aptitude install qt4-doc qt4-doc-html qt4-demos
sudo aptitude install qt-creator (you may not need this)

Create a simple Form with QT4 Designer

Create a folder on disk for your project, for example, my_first_project
Start up QT4 Designer

Select QT 4 Designer from the Applications->Programming menu or...
From a command line terminal run: designer-qt4

The default form is a Dialog with Buttons Right. Stick with that and click Create
Drag a List View from the Item Widgets (Item-Based) selection of widgets on the left onto the form. Be careful NOT to choose the List View from the Item Widgets (Model-Based)
Right-click the List View that is now dragged on the form

Select Edit Items
Click the green plus icon on the left to add an item
Enter the text: First line
Click the green plus icon on the left to add an item
Enter the text: Second line
Click OK to finish editing items

In the Property Editor on the right, scroll down to the section QAbstractItemView
Keep scrolling down a little more to the Property DragDropMode and change it's value to internal. This will let us move items up and down in the list easily
Save what we've done by selecting Save As in the File Menu

Navigate to the folder you created earlier, my_first_project
Choose the filename dashboard.ui for your file and click save
This file contains and XML representation of the form you just created

If you want to take a quick look at your form select Preview from the Form menu
But we're done with GUI stuff now! Let's get hacking...

Creating the basic application structure

Now that we've got a user interface, we need to run a command (rbuic4) that creates a Ruby class that we can use based on the interface
From the command line terminal

Navigate to the my_first_project folder you created earlier using the cd command
Run the command 'rbuic4 dashboard.ui -x -o dashboard_ui.rb'
The '-o dashboard_ui.rb' bit of the command says dump the resulting ruby code into a file called dashboard_ui.rb
The '-x' bit of the command says to create a little stub (like a main function in C/C++ or public static void main in Java) that kicks off the application. Otherwise your application would have no entry point.
We need to rerun this command every time we change the form using QT4 Designer. Usually we won't add the '-x' flag
For instant gratification run the command 'ruby dashboard_ui.rb'
Woaa!!! You should see your beautiful form before you very eyes. But when the excitement dies down, be aware that if you were to add any code to your dashboard_ui.rb file it would get blown away every time we run rbuic4 on this file to pick up the latest changes we made to the UI using QT4 Designer. But it needn't be this way...