Rails - Jul 2007 - HOW TO: Easily output alternating item styles via metaprogramming

I always need to apply alternating item styles when outputting a collection,
here''s what I''ve been using recently.

In the app helper I define this method:

  def alternate(items,alt=false
    items.map{|i| i.class}.each { |k| k.class_eval {attr_accessor :alt}}
    items.each { |i| i.alt, alt = alt, !alt }
  end

When I call the partial I wrap the collection with this method:

<%= render :partial => ''story'', :collection =>
alternate(@stories) %>

Now in the partial each object in the collection has the alt attribute
available:

<li class="<%= story.alt ? "alt" : ""
%>">


Obviously I''m making the assumption that the objects don''t
already have/use
an alt attribute.  Anyone solving this similarly?

- Nathan

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On 7/3/07, blinking bear
<blinkingbear-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
>
> I always need to apply alternating item styles when outputting a
> collection, here''s what I''ve been using recently.
>
> In the app helper I define this method:
>
>   def alternate(items,alt=false
>     items.map{|i| i.class}.each { |k| k.class_eval {attr_accessor :alt}}
>     items.each { |i| i.alt, alt = alt, !alt }
>   end
>
> When I call the partial I wrap the collection with this method:
>
> <%= render :partial => ''story'', :collection =>
alternate(@stories) %>
>
> Now in the partial each object in the collection has the alt attribute
> available:
>
> <li class="<%= story. alt ? "alt" : ""
%>">
>
>
> Obviously I''m making the assumption that the objects
don''t already
> have/use an alt attribute.  Anyone solving this similarly?
>
> - Nathan

To be honest I''m not really following your code.

items.each { |i| i.alt, alt = alt, !alt }  What is this doing?

I must be missing something because it seems that every call to alt should
return false from the setup in the alternate method.

My mind went to the cycle method, but I''m not sure if that fits or not
since
I don''t follow your code.

Anyway the docs are
http://api.rubyonrails.org/classes/ActionView/Helpers/TextHelper.html#M000628

Cheers
Daniel

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> <%= render :partial => ''story'', :collection =>
alternate(@stories) %>
> 
> <li class="<%= story.alt ? "alt" : ""
%>">
seems kinda ferocious to me... you could use the partial counter to 
count even uneven objects, and then style them accordingly:

===========some.rhtml==============
<%= render :partial => ''story'', :collection =>
@stories %>

=======_story.rhtml================
<li class="<%= story_counter.modulo(2).nonzero?
''even'' : ''odds'' %>">


works for ya...?

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Shai,
haha - ferocious?  you''re right

your solution worked (just needed another ?):

<li class="<%= story_counter.modulo(2).nonzero? *?*
''even'' : ''odds'' %>">

thanks,
nathan

On 7/3/07, Shai Rosenfeld
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
>
>
>
> > <%= render :partial => ''story'', :collection
=> alternate(@stories) %>
> >
> > <li class="<%= story.alt ? "alt" : ""
%>">
>
> seems kinda ferocious to me... you could use the partial counter to
> count even uneven objects, and then style them accordingly:
>
> ===========some.rhtml==============>
> <%= render :partial => ''story'', :collection =>
@stories %>
>
> =======_story.rhtml================>
> <li class="<%= story_counter.modulo(2).nonzero?
''even'' : ''odds'' %>">
>
>
> works for ya...?
>
> --
> Posted via http://www.ruby-forum.com/.
>
> >
>
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> your solution worked (just needed another ?):
> 
> <li class="<%= story_counter.modulo(2).nonzero? *?*
''even'' : ''odds'' %>">

oh yea, thanks..glad it helps :)

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If you just want to use another style for every odd row, I''m using
something
like this:


<% @page.items.each do |item| %>
   ...
   <tr class="<%= cycle("even", "odd")
%>">
   ...
<% end %>


API: 
http://api.rubyonrails.org/classes/ActionView/Helpers/TextHelper.html#M000628


Regards,
Timo

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