Question

I’m trying to use a list_box to select from different types of conversions. When I start the program and enter a number it does nothing, but if I click the next item in the list_box it works fine. This makes me think my method is not getting it’s value from the list_box. Here’s the code:

    Shoes.app :title=> 'Temperature Converter', :width => 200, :height => 200 do 
  def convert(temp, unit='C')
    if unit == "C"
   (temp.to_i * 9.0 / 5.0) + 32.0
 elsif unit == "F"
   "Fail"
 end
 end
  list_box :items => ["C", "F"], :choose => "C" do |item|
    @unit.text = item.text
  end
  line1 = edit_line :width => 100
  button 'Compute' do
  @result.text = convert(line1.text, @unit.text)
  end
  @unit = para
  @result = para
  end

I tried setting ‘C’ as the default variable but that didn’t work either. Is there a way to force the list_box to send it’s value on startup?

Also, and unrelated, if I remove ‘@unit = para’ from the end it won’t print anything, even the @result. Why is that?

Any help would be awesome.

Answer 1

It probably won’t print anything because your button and list_box are trying to call @unit.text, so you must continue to define @unit.

I think that is possibly the same reason that it won’t choose “C” by default. At the time you choose “C”, @unit is not defined.

Try this:

@list_box = list_box :items => ["C", "F"]
line1 = edit_line :width => 100
button 'Compute' do
  @result.text = convert(line1.text, @unit.text)
end
@unit = para
@list_box.change{|item|
  @unit.text = item.text
}
@list_box.choose("C")

I am unsure whether you need to separate the change method from the list box, but I have done so to be on the safe side.

EDIT: 2012-01-31 13:29

Shoes.app :title=> 'Temperature Converter', :width => 200, :height => 200 do 
  def convert(temp, unit='C')
    @unit.text = unit
    if unit == "C"
      (temp.to_i * 9.0 / 5.0) + 32.0
    elsif unit == "F"
      "Fail"
    end
  end
  @list_box = list_box :items => ["C", "F"]
  line1 = edit_line :width => 100
  button 'Compute' do
    @result.text = convert(line1.text, @list_box.text)
  end
  @unit = para
  @list_box.choose("C")
  @result = para
end