Rails - Jan 2006 - Hash.new{|h,k| h[k] = ""} ... but for views?

I sometimes buy myself a default value for a hash using something like 
this: h = Hash.new{|h,k| h[k] = ""}. I can now pass
''h'' any key and if a
value has not yet been associated with that key I receive an empty 
string.

I would love to do something similar in my partials so that I wouldn''t 
have to worry about passing in every variable that is referenced.

For example, if I have a partial ''_foo.rhtml'' as follows:

  <%= favorite_food %>
  <%= favorite_color %>

... and I attempt to render it with a call of:

  <%= render(:partial => ''foo'',
             :locals => {:favorite_food => "Anything but
natto."}) %>

... then I''ll be scolded since I didn''t provide a value for 
''favorite_color''. I''d rather just give all unassigned
variables a
default value as described in the first paragraph.

Anyone know of a way this can be done?

-- 
Posted via http://www.ruby-forum.com/.

Don Walker wrote:
> I would love to do something similar in my partials so that I
wouldn''t
> have to worry about passing in every variable that is referenced.
<snip>
> Anyone know of a way this can be done?
> 
The first thing that springs to mind is a quick

<% food_color = '''' if food_color.nil? -%>

at the top.  There may be a slicker way, but if there is it escapes me...

-- 
Alex

Alex Young wrote:
> The first thing that springs to mind is a quick
> 
> <% food_color = '''' if food_color.nil? -%>
> 
> at the top.  There may be a slicker way, but if there is it escapes 
> me...
Thanks, but this won''t work because ''food_color''
isn''t defined to call
''nil?'' upon. I could do what I think you intended with:

  <% favorite_food = '''' unless defined?(favorite_food)
%>

... but as you noted it is definitely NOT slick :-)

-- 
Posted via http://www.ruby-forum.com/.

Don Walker wrote:
> Alex Young wrote:
>> The first thing that springs to mind is a quick
>> 
>> <% food_color = '''' if food_color.nil? -%>
>> 
>> at the top.  There may be a slicker way, but if there is it escapes 
>> me...
> 
> Thanks, but this won''t work because ''food_color''
isn''t defined to call
> ''nil?'' upon. I could do what I think you intended with:
> 
>   <% favorite_food = '''' unless defined?(favorite_food)
%>
> 
> ... but as you noted it is definitely NOT slick :-)
Couple of things here...

a = Hash.new("")  should return an empty string if a undefined key is 
used.

I suppose you could set up an before filter for each of your view 
methods that sets default values for each of your instance variables.

_Kevin

-- 
Posted via http://www.ruby-forum.com/.

>
> I would love to do something similar in my partials so that I
wouldn''t
> have to worry about passing in every variable that is referenced.

class Foo < ActiveRecord::Base

  alias_method :old_favorite_food, :favorite_food
  def favorite_food
    self.old_favorite_food ||= "pizza"
  end

end

The above redefines the getter so it will never return nil.

-Brian Buckley
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Don Walker wrote:
> Alex Young wrote:
>> The first thing that springs to mind is a quick
>>
>> <% food_color = '''' if food_color.nil? -%>
>>
>> at the top.  There may be a slicker way, but if there is it escapes 
>> me...
> 
> Thanks, but this won''t work because ''food_color''
isn''t defined to call
> ''nil?'' upon. I could do what I think you intended with:
> 
>   <% favorite_food = '''' unless defined?(favorite_food)
%>
> 
> ... but as you noted it is definitely NOT slick :-)
Oops - yes, that''s what I was after :-)

But a bit slicker is (and you can actually do this where you use the <%= 
%> tag, so the default is actually defined where you need it):

<%= food_color ||= ''blue'' %>

That''s a little smarter.

-- 
Alex