Rails 3, partials, optional arguments - is this best way to do this?

Question

Migrating app from php. and have this in the view:

<%=render :partial => "jt-test", :locals => {:info => "here is my info", :hide_location=>true} %>
<br /><br />
<%=render :partial => "jt-test", :locals => {:info => "here is my info"} %>

in _jt-test.html.erb:

My info:<br /> 
<%=info %>

<% if local_assigns.has_key? :hide_location %>
    you want to hide location!
<% end %>

Is the local_assigns the proper / best way to do this? Can I have an unlimited number of local_assigns? Is there a local_assigns for the main view called from the controller?

thx

possible duplicate of [optional local variables in rails partial templates: how do I get out of the (defined? foo) mess?](http://stackoverflow.com/questions/2060561/optional-local-variables-in-rails-partial-templates-how-do-i-get-out-of-the-de) — Ciro Santilli OurBigBook.com, Sep 30 '14 at 16:15

Dave Newton · Accepted Answer · 2011-10-21T16:47:19.127

1

In the main view you'd just use normal action class variables (@whatever_variable_name), and they're assigned in the controller:

class FoosController
  def index
    @foos = Foo.all
  end
end

# template
<% @foos.each |foo| %>
    <%= foo.name %>

You may have unlimited locals in a partial, but if there are a "lot", you might be doing it wrong. consider using an encapsulating object, breaking up the template more, etc.

Rails exposes local variables to partials by their name (info and hide_location in your case). You don't need to look it up using has_key?. See the passing local variables docs in the layout and rendering guide.

edited Oct 21 '11 at 16:47

answered Oct 21 '11 at 16:42

Dave Newton

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You should look up those variables with `has_key?` if they are optional. That is even recommended. Also, it's best practice to reuse partials with local variables and not rely on unknown instance variables. – Draiken Oct 21 '11 at 16:50
@Draiken Sure, if they're optional. The comment about instance variables was targeted at OP's question about "local_assigns for the main view called by the controller", and is correct. – Dave Newton Oct 21 '11 at 16:53
appreciate the work but I'm not really seeing any discussion of optional arguments to partials in the guide. may be I just missed it – timpone Oct 21 '11 at 17:34
@timpone I don't think that's discussed in the guide; I'd use simple map notation instead of `has_key?` -- I just missed that in your question. Here's a [comment on apidock](http://apidock.com/rails/ActionController/Base/render#628-Optional-local-assigns) that mentions it, and [here's an SO post](http://stackoverflow.com/questions/2060561/optional-local-variables-in-rails-partial-templates-how-do-i-get-out-of-the-de) that has some other info. The [ActionView docs](http://api.rubyonrails.org/classes/ActionView/Base.html) also has bits of info. – Dave Newton Oct 21 '11 at 18:49

Chris Ledet · Answer 2 · 2011-10-21T17:24:08.217

1

Rails 3 improves the way you can render partials.

<%= render "jt-test", :info => "here is my info", :hide_location => true %>
<br /><br />
<%= render "jt-test", :info => "here is my info", :hide_location => false %>

in _jt-test.html.erb:

My info:<br /> 
<%= info %>

<% unless hide_location %>
  you want to hide location!
<% end %>

Is the local_assigns the proper / best way to do this?

The above is the preferred way of rendering partials with Rails 3

Can I have an unlimited number of local_assigns?

You're limited by memory.

Is there a local_assigns for the main view called from the controller?

Not sure but why would you want to do that. Keep view logic out of the controllers.

edited Oct 21 '11 at 17:24

answered Oct 21 '11 at 16:51

Chris Ledet

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this looks like better syntax than the :locals – timpone Oct 21 '11 at 16:53
Hmm.... I'm getting an `undefined local variable or method 'hide_location' ` error. I'm sure this is probably an error on my part – timpone Oct 21 '11 at 17:20
No, it's an error on my part. You can just keep the variables consistent and assign nil to them so you dont get the error like you did. – Chris Ledet Oct 21 '11 at 17:24

score 0 · Answer 3 · answered Oct 21 '11 at 16:54

0

Like Dave said, if you have a lot of optional variables, you might be better off encapsulating an object and passing it to the partial, but in the case of checking for optional local assigns, the has_key? method is the best way to go.

answered Oct 21 '11 at 16:54

Draiken

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Rails 3, partials, optional arguments - is this best way to do this?

3 Answers3