# Visualruby: combobox example

**URL:** <https://www.ruby-forum.com/t/visualruby-combobox-example/223341>\
**Category:** Ruby-Gnome 2\
**Created:** [September 30, 2012, 8:34pm UTC](https://www.ruby-forum.com/t/visualruby-combobox-example/223341 "2012-09-30T20:34:08Z")\
**Posts on this page:** 17\
**Page:** 1

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**Author:** ![aris](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/258eb7/32.png) [@aris](https://www.ruby-forum.com/u/aris)\
**Post date:** [September 30, 2012, 8:34pm UTC](https://www.ruby-forum.com/t/visualruby-combobox-example/223341/1 "2012-09-30T20:34:08Z")

</div>

Hi

I’m on my first steps with visualruby, in glade gui editor I created a  
combobox1.

Can someone help me to predefine the values by using combArray =  
[“plane”, “ship”, “car”]

and how to read out the selected value from within the calling class?

BR  
Pat

---

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**Author:** ![patrik\_k](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/977dab/32.png) [@patrik\_k](https://www.ruby-forum.com/u/patrik_k)\
**Post date:** [October 3, 2012, 9:49pm UTC](https://www.ruby-forum.com/t/visualruby-combobox-example/223341/2 "2012-10-03T21:49:02Z")

</div>

#!/usr/bin/env ruby  
require ‘gtk2’

combArray = [“plane”, “ship”, “car”]  
store = Gtk::ListStore.new(String)  
combArray.each\_with\_index do |e|  
iter = store.append  
iter[0] = e  
end

cb = Gtk::ComboBox.new(true)  
cb.model = store

window = Gtk::Window.new(“Load Array Into ComboBox”)  
window.resizable = true  
window.border\_width = 10  
window.signal\_connect(‘destroy’) { Gtk.main\_quit }  
window.set\_size\_request(300, -1)  
window.add(cb)  
window.show\_all  
Gtk.main

---

<div class="post-metadata">

**Author:** ![patrik\_k](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/977dab/32.png) [@patrik\_k](https://www.ruby-forum.com/u/patrik_k)\
**Post date:** [October 3, 2012, 9:53pm UTC](https://www.ruby-forum.com/t/visualruby-combobox-example/223341/3 "2012-10-03T21:53:24Z")

</div>

Of course you will have to do something like:

combArray = [“plane”, “ship”, “car”]  
store = Gtk::ListStore.new(String)  
combArray.each do |e|  
iter = store.append  
iter[0] = e  
end

cb = # Gget combo box from visual ruby  
cb.model = store

---

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**Author:** ![patrik\_k](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/977dab/32.png) [@patrik\_k](https://www.ruby-forum.com/u/patrik_k)\
**Post date:** [October 3, 2012, 11:26pm UTC](https://www.ruby-forum.com/t/visualruby-combobox-example/223341/4 "2012-10-03T23:26:53Z")

</div>

Igor P. wrote in post #1078548:

> #!/usr/bin/env ruby  
> require ‘gtk2’

yes thats working, but its not visualruby!

---

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**Author:** ![patrik\_k](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/977dab/32.png) [@patrik\_k](https://www.ruby-forum.com/u/patrik_k)\
**Post date:** [October 4, 2012, 7:58pm UTC](https://www.ruby-forum.com/t/visualruby-combobox-example/223341/5 "2012-10-04T19:58:41Z")

</div>

If VisualRuby was working as expected, you should be able to initialiye  
your ‘MyClass’ with the following code:

def initialize  
combArray = [“plane”, “ship”, “car”]  
store = Gtk::ListStore.new(String)  
combArray.each do |e|  
iter = store.append  
iter[0] = e  
end  
cb = @builder[“combobox1”]  
cb.model = store  
end

However, there seems to be a problem in VR, namely, it ‘@builder’  
variable contains nil! Because of this the initialization of ‘MyClass’  
fails.

---

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**Author:** ![patrik\_k](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/977dab/32.png) [@patrik\_k](https://www.ruby-forum.com/u/patrik_k)\
**Post date:** [October 3, 2012, 11:31pm UTC](https://www.ruby-forum.com/t/visualruby-combobox-example/223341/6 "2012-10-03T23:31:02Z")

</div>

Igor P. wrote in post #1078549:

> cb = # Get combo box from visual ruby  
> cb.model = store

The real trick is to get the combo box, but how?

So I found this one:  
[http://stackoverflow.com/questions/1194659/how-to-use-fill-a-combo-box-with-ruby-glade-3](http://stackoverflow.com/questions/1194659/how-to-use-fill-a-combo-box-with-ruby-glade-3)  
combo = VR::SimpleComboBoxEntry(“Selected”, “Option1”, “option2”,  
“Option3”)  
@builder[“combobox1”].add(combo)

looks very simple but fails with:  
undefined method SimpleComboBoxEntry for VR module

([http://ruby-doc.org/gems/docs/v/vrlib-0.0.32/VR/SimpleComboBoxEntry.html](http://ruby-doc.org/gems/docs/v/vrlib-0.0.32/VR/SimpleComboBoxEntry.html))

---

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**Author:** ![patrik\_k](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/977dab/32.png) [@patrik\_k](https://www.ruby-forum.com/u/patrik_k)\
**Post date:** [October 4, 2012, 9:05pm UTC](https://www.ruby-forum.com/t/visualruby-combobox-example/223341/7 "2012-10-04T21:05:17Z")

</div>

Sorry, I missed one thing before {{ load\_glade( **FILE** ) }}.

def initialize  
load\_glade( **FILE** )  
combArray = [“plane”, “ship”, “car”]  
store = Gtk::ListStore.new(String)  
combArray.each do |e|  
iter = store.append  
iter[0] = e  
end  
cb = @builder[“combobox1”]  
cb.model = store  
end

This now works. However, it does not load the model. You may also have  
to define the model in Glade?!

I do not know enough about VB, but you should do something along the  
following:

combobox1 -\> General tab -\> ComboBox model -\>   
[…] (click the ellipsis) -\> New -\> liststore1

But I still think, that you should be able to write your own code in  
ruby (as we did in the initialize method above for ‘MyClass’), rather  
than messing up with Glade.

---

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**Author:** ![patrik\_k](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/977dab/32.png) [@patrik\_k](https://www.ruby-forum.com/u/patrik_k)\
**Post date:** [October 5, 2012, 8:38pm UTC](https://www.ruby-forum.com/t/visualruby-combobox-example/223341/8 "2012-10-05T20:38:34Z")

</div>

Hi,

VR doesn’t initialize the Gtk::ComboBox correctly. It looks as if VR’s  
combobox constructor is always called with the argument false. Anyhow,  
it seems not only is the run-time assignment of different data model to  
a VR combo-box not working, initialization of VR’s combo-box too, looks  
like a generic VR/Glade problem!?

Both, GTK+ and Ruby-GTK allow to dynamically change the models for any  
combo-box.

I have tested Gtk::ComboBox in VR with both, (1) the model created in  
Glade, (2) and the one generated manually in initialize method. It  
turned out that VR’s ComboBox object is aware of both and can even  
combine them, i.e. you can append programmatically items to the Glade  
generated model, if you so desire. However, VR fails to display either  
of them regardless of how you set up the respective model values (rows).

You can tinker with the following code in VR’s “MyClass”, and see for  
yourself that all items are available to ‘cb’ (combobox) object in VR:

* * *

class MyClass #(change name)

include GladeGUI

def initialize  
load\_glade( **FILE** )  
combArray = [“plane”, “ship”, “car”]  
store = Gtk::ListStore.new(String)

# store = @builder[“liststore1”]

```
combArray.each do |e|
  iter = store.append
  iter[0] = e
end
puts "DEBUG: @builder.class=#{@builder.class} " +
     "store.class=#{store.class}"

cb = @builder["combobox1"]
cb.set_model(store)
cb.active = 3
puts "DEBUG: active_text=#{cb.active_text}"

```

end

## def show() load\_glade( **FILE** ) #loads glade/MyClass.glade into @builder @label1 = “Hello World” set\_glade\_all() #populates glade controls with instance variables show\_window() end end

If you correctly initialize the ‘liststore1’ in Glade, and also set a  
few columns, say (“horse”, “bicycle”, “rollers”), values in it, you can  
combine the model rows (“plane”, “ship”, “car”) defined programmatically  
in MyClass’s ‘initialize’ with the model rows (“horse”, “bicycle”,  
“rollers”) defined in Glade into a single VR’s “cb” list (“horse”,  
“bicycle”, “rollers”, “plane”, “ship”, “car”), by uncommenting // store  
= @builder[“liststore1”] // line in the above listing. To confirm that  
VR’s combobox contains both lists you can first set [//cb.active](https://cb.active) = 0//,  
and in the next test run to ‘4’ ([//cb.active](https://cb.active) = 4//). The two VR test  
runs will in //puts “DEBUG: active\_text=#{cb.active\_text}”// correctly  
print ‘horse’ and ‘ship’ respectively.

For this test to work for both programmatically set model and the one  
set in Glade, you have to assign ‘liststore1’ ‘to tour combobox1’ in  
Glade. Also in Glade under “Add and remove columns” you have to set up  
liststore1’s “Column type” to “gchararray” data type. And lastly, under  
“Add and remove rows” add for example the rows as suggested above  
(“horse”, “bicycle”, “rollers”) to the ‘liststore1’.

---

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**Author:** ![patrik\_k](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/977dab/32.png) [@patrik\_k](https://www.ruby-forum.com/u/patrik_k)\
**Post date:** [October 9, 2012, 12:05am UTC](https://www.ruby-forum.com/t/visualruby-combobox-example/223341/9 "2012-10-09T00:05:11Z")

</div>

Igor P. wrote in post #1078751:

> VR doesn’t initialize the Gtk::ComboBox correctly.

Hi Ivan

I gave it a quick try today, but the box remained empty.  
Yes, I set the fields in Glade. The ComboBox model I set to liststore1.  
Columntype and Column name to gchararray. And added Data rows with  
“horse”, “bicycle”, “rollers”

The debugger shows:  
C:/Ruby193/lib/ruby/gems/1.9.1/gems/vrlib-0.0.32/lib/GladeGUI.rb: line  
127  
GLib-GObject-CRITICAL \*\*:g\_value\_unset: assertion `G\_IS\_VALUE  
(value)’ failed  
DEBUG: @builder.class=Gtk::Builder store.class=Gtk::ListStore  
DEBUG: active\_text=

BR  
Patrik

---

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**Author:** ![patrik\_k](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/977dab/32.png) [@patrik\_k](https://www.ruby-forum.com/u/patrik_k)\
**Post date:** [October 9, 2012, 6:19pm UTC](https://www.ruby-forum.com/t/visualruby-combobox-example/223341/10 "2012-10-09T18:19:23Z")

</div>

Patrick,

I can not reproduce your {{ GLib-GObject-CRITICAL \*\*:g\_value\_unset }}  
error. It looks that you are running Windows, I am on Linux. Perhaps the  
two implementations differ, since the line 127 in GladeGUI.rb, on Linux  
would not spit out your {{ GLib-GObject-CRITICAL \*\*:g\_value\_unset }}  
error. Nevertheless, your debug output line {{ DEBUG: active\_text= }}  
indicates that the two models did not merge. Try changing the {{  
cb.active }} from 3 to 0, and comment out the line {{ store =  
@builder[“liststore1”] }} in your MyClass::initialize. And re-run this  
test in VR. You should get {{ DEBUG: active\_text=plane }}, providing  
your {{ initialize }} method in MyClass looks like the following:

def initialize  
load\_glade( **FILE** )  
combArray = [“plane”, “ship”, “car”]  
store = Gtk::ListStore.new(String)

# store = @builder[“liststore1”]

```
combArray.each do |e|
  iter = store.append
  iter[0] = e
end
puts "DEBUG: @builder.class=#{@builder.class} " +
     "store.class=#{store.class}"

cb = @builder["combobox1"]
cb.set_model(store)
cb.active = 0
puts "DEBUG: active_text=#{cb.active_text}"

```

end

I can show you the code that works in pure Ruby GTK, to prove that it is  
possible to dynamically switch models for Gtk::ComboBox.

Regards, igor

---

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**Author:** ![patrik\_k](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/977dab/32.png) [@patrik\_k](https://www.ruby-forum.com/u/patrik_k)\
**Post date:** [November 12, 2012, 3:25am UTC](https://www.ruby-forum.com/t/visualruby-combobox-example/223341/11 "2012-11-12T03:25:06Z")

</div>

Sorry for the late response.

I would suggest that you never place a combobox in your glade form using  
the glade software for 2 reasons:

1. The glade program has a bug in it so you can’t create a simple  
combobox. There are two types of comboboxes, and it always uses the  
complicated type that requires a liststore object. If you want a simple  
combobox that has one column of choices, use the VR::SimpleComboBoxEntry  
class. (See below)

2. I beleive it is a bad idea to try to populate your combobox using a  
liststore object in glade because you’ll always want to dynamically  
populate the list at runtime using ruby code later anyway. So, do all  
work with the data in code.

This is how you use comboboxes in visualruby:

1. In your glade form, place a vbox object where you want your combobox  
to appear. For this example, the name if the vBox will be “vbox1.” (we  
will insert a combobox inside it using code)

2. In your show() method, create a VR::SimpleComboBoxEntry:

def show()  
load\_glade( **FILE** )  
@cb = VR::SimpleComboBoxEntry.new(“plane”, “ship”, “car”)  
@builder[“vbox1”].add(@cb)  
show\_window()  
end

1. Later, you can retrieve the selected text like this:

def buttonSave\_\_clicked  
@var = @cb.active\_text  
destroy\_window()  
end

The reason I wrote a class to make a simple combobox is because its  
impossible to create with glade alone.

Good luck,  
Eric

---

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**Author:** ![patrik\_k](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/977dab/32.png) [@patrik\_k](https://www.ruby-forum.com/u/patrik_k)\
**Post date:** [November 28, 2012, 10:20pm UTC](https://www.ruby-forum.com/t/visualruby-combobox-example/223341/12 "2012-11-28T22:20:18Z")

</div>

Eric C. wrote in post #1084015:

> 1. In your show() method, create a VR::SimpleComboBoxEntry:
> 
> def show()  
> load\_glade( **FILE** )  
> @cb = VR::SimpleComboBoxEntry.new(“plane”, “ship”, “car”)  
> @builder[“vbox1”].add(@cb)  
> show\_window()  
> end

How could I then react on the change signal from this combobox ??

Greetings

Klaus

---

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**Author:** ![patrik\_k](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/977dab/32.png) [@patrik\_k](https://www.ruby-forum.com/u/patrik_k)\
**Post date:** [November 18, 2012, 8:35pm UTC](https://www.ruby-forum.com/t/visualruby-combobox-example/223341/13 "2012-11-18T20:35:25Z")

</div>

Thanks a lot Eric

With this I think I now have what I need.  
GUI’s without comboboxes would be very boring.

Thanks  
Pat

---

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**Author:** ![patrik\_k](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/977dab/32.png) [@patrik\_k](https://www.ruby-forum.com/u/patrik_k)\
**Post date:** [November 29, 2012, 12:15am UTC](https://www.ruby-forum.com/t/visualruby-combobox-example/223341/14 "2012-11-29T00:15:43Z")

</div>

Klaus D. wrote in post #1086961:

> Eric C. wrote in post #1084015:
> 
> > 1. In your show() method, create a VR::SimpleComboBoxEntry:
> > 
> > def show()  
> > load\_glade( **FILE** )  
> > @cb = VR::SimpleComboBoxEntry.new(“plane”, “ship”, “car”)  
> > @builder[“vbox1”].add(@cb)  
> > show\_window()  
> > end
> 
> How could I then react on the change signal from this combobox ??
> 
> Greetings
> 
> Klaus

Ok, I found it 😉  
I have to manually connect the signal:

@cb.signal\_connect “changed” do |w, e|  
cb\_\_changed(w,e)  
end

---

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**Author:** ![patrik\_k](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/977dab/32.png) [@patrik\_k](https://www.ruby-forum.com/u/patrik_k)\
**Post date:** [November 29, 2012, 10:26pm UTC](https://www.ruby-forum.com/t/visualruby-combobox-example/223341/15 "2012-11-29T22:26:41Z")

</div>

Eric C. wrote in post #1086973:

> Hi Klaus:
> 
> Actually, one of the nice things about visualruby is that you don’t need  
> to use the signal\_connect method. Instead, you just give your method a  
> name using the naming convention: “widget\_\_signal” or  
> “instancevariable\_\_signal” or “self\_\_signal” and vr will automatically  
> connect the signal for you:
> 
> def cb\_\_changed(w,e)  
> VR::msg(“the combobox just changed!”)  
> end
> 
> This method will execute when the widget in the @cb variable emits the  
> “changed” signal.
> 
> Good luck,  
> Eric

Hi Eric,

didn’t know about the “instancevariable\_\_signal” part ;-(  
and learned that I have to declare the instancevariable before calling  
load\_glade 😉

Klaus

---

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**Author:** ![patrik\_k](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/977dab/32.png) [@patrik\_k](https://www.ruby-forum.com/u/patrik_k)\
**Post date:** [May 26, 2013, 4:47pm UTC](https://www.ruby-forum.com/t/visualruby-combobox-example/223341/16 "2013-05-26T16:47:40Z")

</div>

Eric C. wrote in post #1084015:

> 1. Later, you can retrieve the selected text like this:
> 
> def buttonSave\_\_clicked  
> @var = @cb.active\_text  
> destroy\_window()  
> end

And how do I access a combobox value in a listview? I’m trying to check  
value of another cell in a row in a validation block but fail to. It  
seems that I can access only ComboCol and it doesn’t have a  
“active\_text” method.  
I’m lost. 🙂

Here’s my code:

self.renderer(:get\_formats).validate\_block = Proc.new { | value, row |  
if row[:formats].active\_text == “”  
@yt.get\_formats(row)  
row[:formats] = VR::ComboCol.new(“Choose”,  
\*@yt.videos[row.to\_s.to\_i].formats)  
end  
}

It returns with error:  
undefined method `active\_text’ for #VR::ComboCol:0x00000002eac7c8

Cheers,  
k

---

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**Author:** ![patrik\_k](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/977dab/32.png) [@patrik\_k](https://www.ruby-forum.com/u/patrik_k)\
**Post date:** [November 29, 2012, 12:58am UTC](https://www.ruby-forum.com/t/visualruby-combobox-example/223341/17 "2012-11-29T00:58:24Z")

</div>

Hi Klaus:

Actually, one of the nice things about visualruby is that you don’t need  
to use the signal\_connect method. Instead, you just give your method a  
name using the naming convention: “widget\_\_signal” or  
“instancevariable\_\_signal” or “self\_\_signal” and vr will automatically  
connect the signal for you:

def cb\_\_changed(w,e)  
VR::msg(“the combobox just changed!”)  
end

This method will execute when the widget in the @cb variable emits the  
“changed” signal.

Good luck,  
Eric