HowTo : ComboBox widget

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wxRuby ComboBox Widget

This wxRuby guide demonstrates how to use the Wx::ComboBox widget with it’s various styles, features and functions. A complete list of options will be included here together with code examples for your convenience.

wxRuby ComboBox syntax

The syntax for creating a ComboBox widget in wxRuby is as follows:

cb = Wx::ComboBox.new(parent, id, value, pos, size, choices, style, validator, name)

Parameter descriptions:

• parent : Wx::Window
  the parent window (widget) such as a Wx::Panel.
• id : Integer
  Button ID. Wx::ID_ANY indicates a default value.
• value : String
  Optional text to display in the widget as the initial selection. Default is empty string.
• pos : Array(Integer,Integer) or Wx::Point
  Optional coordinates for the position of the topleft corner of the widget. Default is Wx::DEFAULT_POSITION.
• size : Array(Integer,Integer) or Wx::Size
  Optional dimensions of the widget. Default is Wx::DEFAULT_SIZE.
• choices : Array<String>
  A list of strings which will be used as options for the Combobox. Default is nil (no options).
• style : Integer
  Optional styling mask for the button (such as alignment). Default is 0.
• validator : Wx::Validator
  Optional Window validator. Default is nil.
• name : String
  Optional window name. Default is Wx::COMBO_BOX_NAME_STR.

Note: As with all windows, keyword constructor alternatives for all arguments but the 'parent' argument are available. See here for more information.

ComboBox Styles

Available styles for the ComboBox widget:

Button Style	Description
Wx::CB_SIMPLE	Creates a combobox with a permanently displayed list (WXMSW only)
Wx::CB_DROPDOWN	Creates a combobox with a drop-down list
Wx::CB_READONLY	This prevents the User from editing the text and entering a choice of their own (behaves similar to a Wx::Choice).
Wx::CB_SORT	Sorts the entries in the list alphabetically
Wx::TE_PROCESS_ENTER	If enabled, it will enable the generation of the Wx::EVT_TEXT_ENTER event.

ComboBox Methods

A list of useful methods which can be used on the ComboBox widget.

Method	Description
find_string(string, case)	Searches for an Item that matches the given string, and returns it’s index position.
get_count	Returns the number of Items in the ComboBox.
get_current_selection	Returns the index number of the Item currently being selected.
get_string_selection	Returns the string label of the currently selected Item.
get_selection	Returns the index number of the selected Item.
get_string(n)	Returns the Label of the Item at the given index position.
set_selection(n)	Sets the selection to the Item at the given index position.
set_string(n, text)	Sets the Label of the Item at the given index position to the give String.
set_value(text)	Sets the text for the combobox text field

ComboBox Events

A list of event connector methods which can be used for the ComboBox widget.

Event connector	Description
evt_combobox	Connects handler for Wx::EVT_COMBOBOX event which occurs when an item in the list of the ComboBox is selected.
evt_text	Connects handler for Wx::EVT_TEXT which occurs when the text in the ComboBox is changed.
evt_text_enter	Connects handler for Wx::EVT_TEXT_ENTER which occurs when RETURN is pressed in the ComboBox.
evt_combobox_dropdown	Connects handler for Wx::EVT_COMBOBOX_DROPDOWN which occurs when the drop-down list of the ComboBox is displayed.
evt_combobox_closeup	Connects handler for Wx::EVT_COMBOBOX_CLOSEUP which occurs when the drop-down list of the ComboBox closes.

Example Code

In this example we create a basic ComboBox widget and connect it to a method.

After creating the base code, we create a list of strings, which will be used as options on the ComboBox. As the initial value, we simply assign the first value in the array.

Lastly, we connect the Wx::EVT_COMBOBOX event to the combo_box_event method, which prints out the label of the currently selected item.

require 'wx'

class MyWindow < Wx::Frame
  def initialize(title)
    super(nil, title: title)
    @panel = Wx::Panel.new(self)

    values = ["Butter", "Milk", "Biscuits", "Cheese"]

    cb = Wx::ComboBox.new(@panel, value: values.first, choices: values, pos: [50, 50])

    evt_combobox(cb, :combo_box_event)
    
    centre
  end

  def combo_box_event(e)
    cb = e.get_event_object
    puts cb.get_string_selection
  end
end

Wx::App.run do
  window = MyWindow.new("wxRuby ComboBox Guide")
  window.show
end

The output of the above code when the 'Milk' options is selected: