QtRuby connect signals and slots with parameters/arguments

qt, qt4, qtruby, ruby

Solution

The short answer to your question is that you must declare your method signature for the slot to connect to, using the `slots` method:

class MainGUI < Qt::MainWindow
  # Declare all the custom slots that we will connect to
  # Can also use Symbol for slots with no params, e.g. :open and :save
  slots 'open()', 'save()',
        'tree_selected(const QModelIndex &,const QModelIndex &)'

  def initialize(parent=nil)
    super
    @ui = Ui_MainWin.new # Created by rbuic4 compiling a Qt Designer .ui file
    @ui.setupUi(self)    # Create the interface elements from Qt Designer
    connect_menus!
    populate_tree!
  end

  def connect_menus!
    # Fully explicit connection
    connect @ui.actionOpen, SIGNAL('triggered()'), self, SLOT('open()')

    # You can omit the third parameter if it is self
    connect @ui.actionSave, SIGNAL('triggered()'), SLOT('save()')

    # close() is provided by Qt::MainWindow, so we did not need to declare it
    connect @ui.actionQuit,   SIGNAL('triggered()'), SLOT('close()')       
  end

  # Add items to my QTreeView, notify me when the selection changes
  def populate_tree!
    tree = @ui.mytree
    tree.model = MyModel.new(self) # Inherits from Qt::AbstractItemModel
    connect(
      tree.selectionModel,
      SIGNAL('currentChanged(const QModelIndex &, const QModelIndex &)'),
      SLOT('tree_selected(const QModelIndex &,const QModelIndex &)')
    )
  end

  def tree_selected( current_index, previous_index )
    # …handle the selection change…
  end

  def open
    # …handle file open…
  end

  def save
    # …handle file save…
  end
end

Note that the signatures passed to `SIGNAL` and `SLOT` do not include any variable names.

Also, as you concluded in your comment, it is simpler (and more Ruby-esque) to do away with the "slot" concept altogether and just use a Ruby block to connect the signal to invoke whatever method you like (or put the logic inline). Using the following syntax, you do not need to use the `slots` method to pre-declare your method or handling code.

changed = SIGNAL('currentChanged(const QModelIndex &, const QModelIndex &)')

# Call my method directly
@ui.mytree.selectionMode.connect( changed, &method(:tree_selected) )

# Alternatively, just put the logic in the same spot as the connection
@ui.mytree.selectionMode.connect( changed ) do |current_index, previous_index|
  # …handle the change here…
end

Problem

I would like to know how I can connect to a signal that take parameters (using Ruby blocks). I know how to connect to one which does not take parameters: ``` myCheckbox.connect(SIGNAL :clicked) { doStuff } ``` However, this does not work: ``` myCheckbox.connect(SIGNAL :toggle) { doStuff } ``` It doesn't work because the toggle slot take a parameter `void QAbstractButton::toggled ( bool checked )`. How can I make it work with parameters? Thanks.

Original source