Languages/Ruby

    From KDE TechBase
    Revision as of 20:42, 29 June 2011 by Neverendingo (talk | contribs) (Text replace - "<code ruby>" to "<syntaxhighlight lang="ruby">")


    Development/Languages/Ruby

    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: <syntaxhighlight lang="ruby">

    1. !/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:

    <syntaxhighlight lang="ruby"> 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('Hello Qt in the Ruby way!')
           
           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:

    <syntaxhighlight lang="ruby"> create_standard_status_bar_action() createStandardStatusBarAction()

    Operator overloading

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

    <syntaxhighlight lang="ruby"> 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:

    <syntaxhighlight lang="ruby"> slots 'setColor(QColor)', 'slotLoad(const QString&)'.. signals 'clicked()'..

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

    <syntaxhighlight lang="ruby"> 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:

    <syntaxhighlight lang="ruby"> Qt::Object.connect( @colormenu, SIGNAL( "activated(int)" ),

                     self, SLOT( "slotColorMenu(int)" ) )
    

    There is also two another possibilities:

    <syntaxhighlight lang="ruby"> connect(:mysig, mytarget, :mymethod)) connect(SIGNAL('mysignal(int)'), mytarget, :mymethod))

    Or you can connect signal to a block:

    <syntaxhighlight lang="ruby"> quit_button.connect(SIGNAL :clicked) { $qApp.quit }

    And emit signals like this:

    <syntaxhighlight lang="ruby"> 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 <syntaxhighlight lang="ruby"> 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 <syntaxhighlight lang="ruby"> 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 <syntaxhighlight lang="ruby"> 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.

    <syntaxhighlight lang="ruby"> 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:

    <syntaxhighlight lang="ruby"> quit = Qt::PushButton.new("Quit", self, "quit")

    Or you can pass a block if you prefer:

    <syntaxhighlight lang="ruby"> 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:

    <syntaxhighlight lang="ruby"> 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:

    <syntaxhighlight lang="ruby"> 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:

    <syntaxhighlight lang="ruby"> 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()':

    <syntaxhighlight lang="ruby">

    1. static Ptr findByFileContent( const QString &fileName,
    2. 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:

    <syntaxhighlight lang="ruby">

    1. QFont getFont(bool * ok, const QFont&initial,
    2. 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?

    1. font is set to the font the user selected

    else

    1. 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:

    <syntaxhighlight lang="ruby"> 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:

    <syntaxhighlight lang="ruby"> Qt::Internal::setDebug(Qt::QtDebugChannel::QTDB_VIRTUAL)

    Or trace QtRuby garbage collection:

    <syntaxhighlight lang="ruby"> 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:

    <syntaxhighlight lang="bash"> $ rbuic mainform.ui -x -o mainform.rb

    Will add this to the end of the generated code:

    <syntaxhighlight lang="ruby"> 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:

    <syntaxhighlight lang="bash"> $ rbuic4 -x -kde knotifywidgetbase.ui -o knotifywidgetbase.rb

    Will generate this top level code:

    <syntaxhighlight lang="ruby"> 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

    Warning
    This section needs improvements: Please help us to

    cleanup confusing sections and fix sections which contain a todo


    Remove example that does not work

    You can load a Qt Designer .ui file at runtime with the 'quiloader' extension, for example:

          require 'Qt4'
          require 'quiloader'
    
          a = Qt::Application.new(ARGV)
          if ARGV.length == 0
            exit
          end
    
          if ARGV.length == 2
            QUI::WidgetFactory.loadImages ARGV[0]
            w = QUI::WidgetFactory.create ARGV[1]
            if w.nil?
              exit
            end
            w.show()
            a.connect(a, SIGNAL('lastWindowClosed()'), a, SLOT('quit()'))
            a.exec()
          end
    

    With new version API changed a little.

          require 'Qt4'
          require 'qtuitools'
    
          a = Qt::Application.new(ARGV)
          if ARGV.length == 0
            exit
          end
    
          if ARGV.length == 1
            file = Qt::File.new(ARGV[0])
            file.open(Qt::File::ReadOnly)
    
            loader = Qt::UiLoader.new
            window = loader.load(file, nil)
            file.close
    
            if (window.nil?)
              print "Error. Window is nil.\n"
              exit
            end
            window.show
            a.connect(a, SIGNAL('lastWindowClosed()'), a, SLOT('quit()'))
            a.exec
          end
    

    API reference

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

    <syntaxhighlight lang="bash"> $ rbqtapi Qt::TextEdit

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

    <syntaxhighlight lang="bash"> $ 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.

    <syntaxhighlight lang="ruby"> 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:

    <syntaxhighlight lang="ruby"> 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

    <syntaxhighlight lang="ruby">

         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 <syntaxhighlight lang="ruby"> 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 <syntaxhighlight lang="ruby">require 'Qt4', use<syntaxhighlight lang="ruby">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:

    <syntaxhighlight lang="bash"> $ 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):