Languages/Ruby

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Note

The information below applies to older versions of Qt only. There are currently no Ruby bindings for Qt 5 and KDE Frameworks 5 available.

Warning

Some important links are non-functional, specially the official Korundum page. Until we solve this problem you can find the source code at kdebindings project page

Very complete bindings to both the KDE API and the Qt APIs. The Korundum package includes both a QtRuby Qt-only binding along with the full combined Qt/KDE one. The QtRuby package contains just Qt bindings with no dependencies on KDE.

Korundum/QtRuby - Ruby-KDE/Qt bindings

The book Rapid GUI Development with QtRuby (for Qt version 3.x) is available.

Being Smoke-based bindings means that they offer full access to most KDE 4.x and Qt 4.x classes.

QtRuby

Hello world example:

#!/usr/bin/ruby -w
require 'Qt4'
a = Qt::Application.new(ARGV)
hello = Qt::PushButton.new("Hello World!")
hello.resize(100, 30)
hello.show
a.exec

Hello Qt example in a more 'Rubyish' way:

require 'Qt4'

Qt::Application.new(ARGV) do
    Qt::Widget.new do

        self.window_title = 'Hello QtRuby v1.0'
        resize(200, 100)
    
        button = Qt::PushButton.new('Quit') do
            connect(SIGNAL :clicked) { Qt::Application.instance.quit }
        end

        label = Qt::Label.new('<big>Hello Qt in the Ruby way!</big>')
        
        self.layout = Qt::VBoxLayout.new do
            add_widget(label, 0, Qt::AlignCenter)
            add_widget(button, 0, Qt::AlignRight)
        end
        
        show
    end
    
    exec
end

Current api coverage overview

Available calls

You can call all Qt public and protected methods, and all friend methods such as bitBlt() etc

Virtual methods

All virtual methods can be overridden, not just event handlers

Properties

'foobar = 5' is a synonym for 'setFooBar(5)'

Use either CamelCase or lowercase with underscore naming

Any underscores in method names are removed, and the following character is capitalised. For example, you can use either of these two forms to call the same method:

create_standard_status_bar_action()
createStandardStatusBarAction()

Operator overloading

The full range of Qt operator methods is available, for example:

p1 = Qt::Point.new(5,5)   => (5, 5)
p2 = Qt::Point.new(20,20) => (20, 20)
p1 + p2                   => (25, 25)

Declare signals and slots

Signals and slots are declared as list of strings like this:

slots 'setColor(QColor)', 'slotLoad(const QString&)'..
signals 'clicked()'..

For slots and signals without arguments you can use Ruby symbols:

slots :slotLoad
signals :clicked

Currently C++ type signatures must be used, a future version of QtRuby will allow ruby type signatures instead. (see the section on emitting Ruby Classes)

Connect slots and signals like this:

Qt::Object.connect( @colormenu, SIGNAL( "activated(int)" ),
                  self, SLOT( "slotColorMenu(int)" ) )

There is also two another possibilities:

connect(:mysig, mytarget, :mymethod))
connect(SIGNAL('mysignal(int)'), mytarget, :mymethod))

Or you can connect signal to a block:

quit_button.connect(SIGNAL :clicked) { $qApp.quit }

And emit signals like this:

emit colorChanged( black )

Emitting Ruby Classes

Ruby classes can be emitted by embedding them inside a QVariant, and emitting the QVariant.

The following code provides a method called to_variant that can be used to easily convert objects to Variants

class Qt::RubyVariant < Qt::Variant
    def initialize(value)
        super()
        @value = value
    end

    attr_accessor :value
end

class Object
    def to_variant
        Qt::RubyVariant.new self
    end
end

Note: as of KDE 4.5 you can simply use

variant = Qt::Variant.fromValue(my_ruby_object)

to create a QVariant that contains your ruby object. To get it back, you just call Qt::Variant#value as usual.

This can be used as follows

class MyObject < Qt::Object
    signals "mySignal(QVariant)"
    def doEmit
        # since KDE 4.5:
        # emit mySignal(Qt::Variant.fromValue(ruby_object))
        emit mySignal(ruby_object.to_variant)
    end

    slots "mySlot(QVariant)"
    def mySlot(variant)
        ruby_object = variant.value
    end
end

Alternate way to emit Ruby Classes

You can also try to emit a ruby class by emitting it's object_id (either as an Integer or a QVariant), and use ObjectSpace._id2ref to get the object back.

class Object
    def to_variant
        Qt::Variant.new object_id
    end
end

class Qt::Variant
    def to_object
        ObjectSpace._id2ref to_int
    end
end

Constructors

You can call constructors in the conventional style:

quit = Qt::PushButton.new("Quit", self, "quit")

Or you can pass a block if you prefer:

w = MyWidget.new { setCaption("foobar") }

The block will be called in the context of the newly created instance.

Ordinary arguments can be provided as well as a block at the end:

w = MyWidget.new(nil) { setCaption("foobar") }

They are run in the context of the new instance.

And there's more! You can also pass an arg to the block, and it will be run in the context of the arg:

w = MyWidget.new { |theWidget| theWidget.setCaption "foobar" }

Garbage Collection

When a ruby instance is garbage collected, the underlying C++ instance will only be deleted if it isn't 'owned' by a parent object. Normally this will 'just work', but there are occasions when you need to delete the C++ ahead of garbage collection, and whether or not it has a parent. Use the dispose(), isDisposed() and disposed? methods like this:

item2.dispose
if item2.disposed?
puts "item2 is disposed"
end

C++ 'int*' and 'int&' argument types

Ruby passes numeric values by value, and so they can't be changed when passed to a method. The Qt::Integer class provides a mutable numeric type which does get updated when passed as an argument. For example, this C++ method 'findByFileContent()':

# static Ptr findByFileContent( const QString &fileName, 
#                               int *accuracy=0 );
 
acc = Qt::Integer.new(0)
fc = KDE::MimeType.findByFileContent("mimetype.rb", acc)

It supports the arithmetic operators, and so expressions such as 'acc + 3' will work.

C++ 'bool*' and 'bool&' argument types

There is a similar problem for bool arg types, and the mutable Qt::Boolean class can be used like this:

# QFont getFont(bool * ok, const QFont&initial, 
#               QWidget* parent = 0, const char *name = 0);		
 		
ok = Qt::Boolean.new
font = Qt::FontDialog.getFont(ok, 
                    Qt::Font.new("Helvetica [Cronyx]", 10), 
                    self)
if !ok.nil? 
# font is set to the font the user selected
else 
# the user canceled the dialog
end

Use 'nil?' to test the value returned in the Boolean

C++ (const )(unsigned )char* argument types

In some cases Qt/KDE object "takes ownership" over Ruby String passed as char* argument type. Programmer needs to make sure that Ruby String is not being garbage collected or changed for the time it's being used by Qt/KDE object. It is also quite possible that Qt/KDE object will change and eventually free it(memory used internally by Ruby String to store its data). Be very careful when you call this kind of methods and make sure that there is no overloaded version witch accepts QString or QByteArray first!

C++ unsigned char* functions

Very few functions (as QImage::bits()) return a uchar* to directly manipulate data. These functions are not supported in Ruby and will throw an ArgumentError. More information on the mail list.

Debugging

If a method call can't be matched in the Smoke library giving a 'method_missing' error, first check that you are passing correct class instance that is properly initialized (with super method called in constructors of custom Qt classes descendants). You can also turn on debugging to trace the matching process:

a = Qt::Application.new(ARGV)
Qt.debug_level = Qt::DebugLevel::High
a.loadLibrary("foo")  # Non existent method

Will give the following output:

      classname    == QApplication
      :: method == loadLibrary$
      -> methodIds == []
      candidate list:
      Possible prototypes:
          static QWidget* QApplication::widgetAt(int, int, bool)
			...

Here, the list of candidate methods 'methodIds' is empty

Another debugging mechanism allows various trace 'channels' to be switched on.

You can trace virtual method callbacks:

Qt::Internal::setDebug(Qt::QtDebugChannel::QTDB_VIRTUAL)

Or trace QtRuby garbage collection:

Qt::Internal::setDebug(Qt::QtDebugChannel::QTDB_GC)

String i18n

QtRuby supports $KCODE values of 'u', 'e' and 's' or the corresponding '-K' options from the command line. Qt Designer .ui files have UTF-8 strings so if you use any 8 bit UTF-8 characters, you will need to set $KCODE='u' or use the -Ku command line option.

Other capabilities and offerings

Qt Designer

A 'rbuic4' tool is included in qtruby/tools/rbuic to compile .ui files into ruby code. As described above, Qt Designer uses UTF-8. In addition to the options in the original uic C++ utility an '-x' flag has been added. This will generate a top level stub in the code:

$ rbuic mainform.ui -x -o mainform.rb

Will add this to the end of the generated code:

if $0 == __FILE__
    a = Qt::Application.new(ARGV)
    w = MainForm.new
    w.show
    a.exec
end

Then you can test the example code straight away:

      $ ruby mainform.rb

Use the '-kde' option to require the 'korundum4' extension rather than the 'Qt4' one. If the '-x' option is used in conjunction, it generates a KDE top level. For example:

$ rbuic4 -x -kde knotifywidgetbase.ui -o knotifywidgetbase.rb

Will generate this top level code:

if $0 == __FILE__
    about = KDE::AboutData.new("knotifywidgetbase", 
 		                       "KNotifyWidgetBase", "0.1")
    KDE::CmdLineArgs.init(ARGV, about)
    a = KDE::Application.new()
    w = KNotifyWidgetBase.new
    w.show
    a.exec
end

Loading .ui files at runtime with Qt::UiLoader

Let's say you created a file in your project directory called 'gui.ui' using Qt Designer ('/usr/bin/designer', comes with Qt. At least on Arch). You can load it like so:

require 'Qt4'
require 'qtuitools'

class MyApp < Qt::Application
    def initialize
        super ARGV

        # 'gui.ui' was created with qt designer ('designer' on arch linux)
        file = Qt::File.new 'gui.ui' do
            open Qt::File::ReadOnly
        end
        
        window = Qt::UiLoader.new.load file

        file.close

        if window.nil?
            print "Error. Window is nil.\n"
            exit
        end 
        window.show
    end
end

a = MyApp.new
a.exec

API reference

Use the bin/rbqtapi tool to discover which methods are available in the QtRuby api. This command:

$ rbqtapi Qt::TextEdit

Will list all the methods in the Qt::TextEdit class

$ rbqtapi -rsetCaption

Lists all methods whose names contain the string 'setCaption'

Example programs

The best way to start programming QtRuby is to look at some existing code and start messing with it.. The are various samples under qtrubyexamples and korundum/examples.

Writing Unit Tests

Using Ruby allows you the power to leverage testing frameworks such as RSpec in order to unit and integration test your classes.

Most classes such as Models can be easily tested via the APIs they expose. Below is a small extract with some interesting tests from the mingle_mover project (http://github.com/gja/mingle_mover). The class being tested is a TableModel

Note how we create a stub to pass to QAbstractTableModel::data, which accepts a QModelIndex as an argument.

describe CardModel do
    it "Should Implement QAbstractTableModel" do
        CardModel.ancestors.should include Qt::AbstractTableModel
    end

    it "Should Not Be Editable" do
        @model.data(mock_index(1,2), Qt::EditRole).should_not be_valid
        @model.headerData(nil, nil, Qt::EditRole).should_not be_valid
        
        flags = @model.flags(nil)
        flags.should have_flag Qt::ItemIsEnabled
        flags.should have_flag Qt::ItemIsSelectable
        flags.should_not have_flag Qt::ItemIsEditable
    end

    it "Should not return any vertical headers" do
        @model.headerData(1, Qt::Vertical).should_not be_valid
    end

    it "Should color a row according to the status" do
        @model.data(mock_index(1,2), Qt::ForegroundRole).value.color.should == Qt::Color.new(Qt::red)
        @model.data(mock_index(0,2), Qt::ForegroundRole).value.color.should == Qt::Color.new(Qt::green)
        @model.data(mock_index(0,0), Qt::ForegroundRole).should_not be_valid
    end

    def mock_index(row, col)
        stub(:row => row, :column => col)
    end

    def have_flag(flag)
        return simple_matcher("A flag that matches " + flag.to_s) { |given| (given & flag) != 0 }
    end
end

Testing Out Signals and Slots

Below is a simple class which can be used to test out a class via the signals it emits:

class RubySignalSpy < Qt::Object
    def self.create(*args, &block)
        Class.new(self).new(*args, &block)
    end

    def count(name)
        @calls[name].size
    end

    def params(name, invocation = 0)
        @calls[name][invocation]
    end

    def method_missing(name, *args, &block)
        @calls[name.to_sym] << args
        exec_action_for(name, args)
    end

    def responds_to?(name)
        true
    end

  private
    def initialize
        @calls = {}
        def @calls.[](index)
            super || self[index] = []
        end
        @actions = {}
        super
    end

    def mocked_slots(*names, &block)
        slots *names
        names.each { |name| @actions[name] = block }
    end

    def exec_action_for(name, args)
        @actions[name].call(self, args) if @actions[name]
    end

    def slots(*args)
        self.class.slots(*args)
    end
end

      it "Should be able to emit a signal when called" do
        reciever = RubySignalSpy.create do
            slots "recieved(int, int)"                      # Explicitly name slots with parameters
            mocked_slot :some_other_slot do |spy, params|   # Pass a block to be executed when called
            end                                             # You must call mocked_slot with a symbol
        end

        class ClassWeAreTesting < Qt::Object
            signals "sending(int, int)"
            def broadcast
                emit sending(4, 2)
            end
        end

        sender = ClassWeAreTesting.new

        Qt::Object.connect(sender, SIGNAL("sending(int, int)"), reciever, SLOT("recieved(int, int)"))
        sender.broadcast
        reciever.count(:recieved).should == 1               # Get count of calls
        reciever.params(:recieved, 0).should == [4, 2]      # Get the parameters of nth invocation
    end

Testing UI Classes

It is much more difficult to test UI classes. In most cases, you will need to instantiate a QApplication so that you can create your widgets.

Some rudimentary tests can be written by simulating clicks are various locations. Watch this space as more tests get written

describe SomeTableView do
    before(:all) do
        @app = Qt::Application.new(ARGV)
        @view = SomeTableView.new
    end

    it "Should accept a mouse click on second row"        
        @row2 = @view.rowViewportPosition 1
        @view.mousePressEvent(Qt::MouseEvent.new(Qt::Event::MouseButtonPress, Qt::Point.new(0,@row2), Qt::LeftButton, Qt::LeftButton, Qt::NoModifier))
        # Assert something here, such as that a signal has been emitted
    end

    after(:all) do
        @app.dispose!
    end
end

KDE Specific Infomation

Instead of

require 'Qt4'

, use

require 'korundum4'

for KDE programs.

The KDE K* classes such as KApplication are renamed as KDE::Application. The other KDE classes are in the KParts::, KIO:: or DOM:: namespaces, with the same names as their C++ counterparts.

Use the 'rbkdeapi' script to introspect the Korundum api from the command line. For example:

$ rbkdeapi KDE::Action

Will list all the methods in the KDE::Action class. There are currently (as at KDE 3.3 beta 2) 977 classes/30841 methods in the Smoke library runtime, so the coverage of the Qt/KDE api is pretty complete.

Build dependencies

• ruby 1.8 or greater (svn trunk works with 1.9.1)
• cmake 2.6 or greater
• Qt 4.0 or greater
• KDE 4.1 or greater (for korundum)

Tutorials

There is a ruby translation of Qt Tutorial #1, and the corresponding ruby code is in qtruby/rubylib/tutorial/t1 to t14.

And a Qt4 version of the same tutorial translated to Ruby by Darshan Ishaya Qt4 Ruby Tutorial

Qt Tutorial #2, a Charting Application with ruby code in qtruby/rubylib/examples/qt-examples/chart.

The Qt Designer Color Tool Tutorial, with ruby code in qtruby/rubylib/designer/examples/colortool.

Paul Lutus has written a tutorial on how to get started with Ruby GUI programming with Qt

For KDE, there is a ruby translation of this KDE 3.0 tutorial originally written for C++ by Antonio Larrosa Jiménez. The sources are in korundum/rubylib/tutorials/p1 to p9.

The book Rapid GUI Development with QtRuby is now available.

There is also an approach to create an Ruby-Qt/KDE Book under a free license. The content will be created in this wiki. The book made with latex will be derived from the content in the wiki. Any Questions? Contact me!

Download

You can obtain recent SVN snapshots on the Rubyforge QtRuby/Korundum site.

More help

There are two IRC channels (#qtruby and #kde-ruby) in FreeNode. If you prefer e-mail, you can use the kde-bindings mailing-list (low traffic) or ask in the ruby-talk mailing list (you may use the Ruby Forum gateway to post in ruby-talk from web).

More information

A series of articles on ruby QT (inspired by the work done for the dradis project):

• ruby workshop: the way of the Qt samurai
• ruby Qt: model / view / controller
• ruby Qt: menu bar, status bar and resources
• ruby Qt custom widget example
• ruby Qt::TreeWidget example
• Very useful link how to create your first Qt window dialog