#847 Pass block args for render :layout - Ruby on Rails

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#847 √ resolved

Pass block args for render :layout

Reported by Ryan Bates | August 16th, 2008 @ 06:58 PM | in 2.2

Currently it's possible to pass a block to "render :layout" in the view and yield to it. For example:


<!-- _layout.html.erb -->
before
<%= yield %>
end

<!-- some view --->
<%= render :layout => 'layout' do %>
middle
<% end %>

<!-- outputs -->
before
middle
end

However, you can not pass any arguments to that block when you yield. The included patch adds this ability. You can then do some really cool stuff like use that as an iterator if you pass a collection to layout.


<!-- _comment.html.erb -->
before
<%= yield comment %>
after

<!-- some view -->
<% render :layout => @comments do |comment| %>
  <%= comment.created_at %>
<% end %>

<!-- output -->
before
2008-01-01 00:00:00 (whatever time the comment was created)
after

This is very useful if you need to dynamically change some part of a partial when you're rendering it.

Comments and changes to this ticket

Ryan Bates August 16th, 2008 @ 07:14 PM

Also, you could get fancy and yield multiple times for different sections of the layout. For example.


<!-- _comment.html.erb -->
before
<%= yield comment, :time %>
middle
<%= yield comment, :extra %>
after

<!-- some view -->
<% render :layout => @comments do |comment, section| %>
  <% case section when :time %>
    <%= comment.created_at %>
  <% when :extra %>
    some extra content
  <% end %>
<% end %>

<!-- output -->
before
2008-01-01 00:00:00 (whatever time the comment was created)
middle
some extra content
after

This way you can easily and dynamically customize various parts of the layout/partial when rendering it.

DHH August 16th, 2008 @ 08:43 PM
I like this, but we need to get some documentation on the method along with the patch.
Ryan Bates August 16th, 2008 @ 08:46 PM
thanks, documentation is planned, just wanted to nail down the functionality first.
Ryan Bates August 16th, 2008 @ 09:15 PM
Here's an updated patch with docs.
Joshua Peek August 17th, 2008 @ 05:05 AM
If @proc_for_layout is private, lets prefix it with an underscore. I started doing that with a few other instance variables that are available in the view scope.

The execute method was always a bad smell on Base. I wonder if we could easily move that over into the Renderable#render method. (This isn't exactly related to your patch buts its always nice to cleanup these little things when we spot them)
Ryan Bates August 17th, 2008 @ 05:29 AM
Here's an updated patch with the underscore prefix. I'm not sure what's involved in moving the execute method over to renderable, so I'll leave that to you. :)
- block_args_for_render_layout_with_docs_2.diff 6.5 KB
Repository August 18th, 2008 @ 01:30 AM
- → State changed from “new” to “resolved”
(from [38c7d73e73d569211c4dfadf96fc295a925b7c9c]) pass yielded arguments to block for ActionView::Base#render with :layout [#847 state:resolved]

Signed-off-by: Joshua Peek josh@joshpeek.com http://github.com/rails/rails/co...
Joshua Peek October 28th, 2008 @ 05:34 PM
- → Milestone changed from “2.x” to “2.2”
- → State changed from “resolved” to “open”
- → Assigned user changed from “” to “Joshua Peek”
Someone found a 2.1 regression bug due to this commit.

The block arguments passed in shadow any existing @content_for_*.
```
# index.erb
<% content_for :column do %>column<% end %>
<% render :layout => 'layouts/column' do %>content<% end %>

# layouts/column.erb
<div id="column"><%= yield :column %></div>
<div id="content"><%= yield %></div>
```
The "yield :column" always returns what is in the block "content" first and it never looks up @content_for_column.

http://gist.github.com/20441
Ryan Bates October 28th, 2008 @ 06:56 PM
This should be fixable by checking for the existence of the @content_for_* instance variable before executing the block. I'll try to write up a patch later today.
Joshua Peek October 28th, 2008 @ 08:36 PM
I was playing with that idea but it got real hairy real fast. Good Luck :)
Ryan Bates October 28th, 2008 @ 08:37 PM
Here's a patch which fixes this problem by checking for the existence of the content_for ivar before executing the block. Your tests are included.
- check_content_for_ivar_in_layout_yield.diff 3.1 KB
Joshua Peek October 29th, 2008 @ 02:23 AM
- → State changed from “open” to “resolved”
O, you make it look so easy :)

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