Rails - Aug 2010 - Rails best practice to check an object’s existence before displaying an attribute in a layout

I have the following code in a layout:

Posted <%=time_ago_in_words post.created_at %> ago
<% if post.has_tag != nil %>
   in the <%= post.get_first_tag.name %> category
<% end %>
And the following code in the post model which is inheriting form
ActiveRecord::Base

def has_tag
 !self.tags.empty?
end

def get_first_tag
 self.tags[0]
end
Tags is also inherited from ActiveRecord::Base and Post
''has_many''
Tags

Firstly: Is this the best way of checking if the post object has at
least 1 associate tag attribute.

Secondly: Should I be putting this logic into a helper method?

Thirdly: Why doesn''t the following work (it returns a # where the tags
should be):

in the <%= post.tags.to_sentence %> category,
I guess its because tags aren''t actually stored as an array attribute,
but i don''t really know.

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ActiveRecord already has helper methods defined, so adding wrappers
like has_tag and get_first_tag is usually not necessary, and only
makes your code more complex.

1. You can do
 <% if post.tags.any? %>
   in the <%= post.tags.first.name %> category
 <% end %>
And remove the get_first_tag and tags methods from your model.

2. This kind of logic is well suited for the view layer (i think).

3. Hard to tell without knowing what tags actually returns. Try using
post.tags.inspect to see what it returns.
I suspect you see ''#'' because the objects in the array
returned by
tags doesn''t have a to_s method defined.
to_sentence converts an array to a string using to_s on each element.

If you have a Tag class, try adding this to that class:
def to_s
  name
end

If you''re using a plugin/gem for the tags, you can either monkepatch
it or do something like this:
post.tags.map(&:name).to_sentence (assuming Tag has a name attribute
you want to display).
This kind of logic is appropriate to put in a helper.

--
gudleik

On Tue, Aug 10, 2010 at 1:23 AM, wtb
<whiskeytangobravo-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org>
wrote:
> I have the following code in a layout:
>
> Posted <%=time_ago_in_words post.created_at %> ago
> <% if post.has_tag != nil %>
>   in the <%= post.get_first_tag.name %> category
> <% end %>
> And the following code in the post model which is inheriting form
> ActiveRecord::Base
>
> def has_tag
>  !self.tags.empty?
> end
>
> def get_first_tag
>  self.tags[0]
> end
> Tags is also inherited from ActiveRecord::Base and Post
''has_many''
> Tags
>
> Firstly: Is this the best way of checking if the post object has at
> least 1 associate tag attribute.
>
> Secondly: Should I be putting this logic into a helper method?
>
> Thirdly: Why doesn''t the following work (it returns a # where the
tags
> should be):
>
> in the <%= post.tags.to_sentence %> category,
> I guess its because tags aren''t actually stored as an array
attribute,
> but i don''t really know.
>
> --
> You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
> To post to this group, send email to
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> To unsubscribe from this group, send email to
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> For more options, visit this group at
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>
>
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On Mon, Aug 9, 2010 at 19:23, wtb
<whiskeytangobravo-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org> wrote:
> <% if post.has_tag != nil %>
...
> def has_tag
>  !self.tags.empty?
> end
false is not the same as nil.  You''ve been hacking too much LISP.  :-)
 Dump the "!= nil", leaving simply "if post.has_tag".

-Dave

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