Render partial from helper_method

Question

Ok so I have a helper method in the application controller:

def run_test(test_name)
  #computation stuff
  render :partial => test_name
end

And I call it like so in views:

<%= run_test("testpartial") %>

and it renders ok with only 1 (although... the render partial seems to be returning an array instead of just the partial content?), but if I put the run_test helper call in the view twice I get a double render error, which shouldn't be happening with partials.

Any ideas?

Which versions of ruby and rails are you using, I don't get this behaviour when running 3.1? — Benoit Garret, Sep 03 '11 at 00:40
3.1. I was using an RC candidate but I upgraded just to be sure and it still isn't working. — Msencenb, Sep 03 '11 at 01:42
Hmmm... So turns out I was defining this helper method in the application_controller using helper_method :run_test however moving it to application_helper file in the helpers folder works. So.. I have a whole in my understanding between the difference of a helper defined in the application controller and a helper defined in a helper file. Anyone able to fill me in? — Msencenb, Sep 03 '11 at 01:50
A method in the application controller is only available to controllers. A method in a helper is only available to views. — drummondj, Sep 03 '11 at 02:17
Thanks John. If you want to add that as an answer I'll gladly mark it as accepted for you :) — Msencenb, Sep 03 '11 at 02:40

numbers1311407 · Accepted Answer · 2011-09-03T03:38:58.720

render in a controller versus render in a view are different methods. The controller eventually calls render on a view, but the controller's render method itself expects to be called only once. It looks like this:

# Check for double render errors and set the content_type after rendering.
def render(*args) #:nodoc:
  raise ::AbstractController::DoubleRenderError if response_body
  super
  self.content_type ||= Mime[formats.first].to_s
  response_body
end

Note how it raises if called more than once?

When you call helper_method you give the view a proxy to the controller's version of render, which is not intended to be used in the same way as ActionView's, which is, unlike the controller's, expected to be called repeated to render partials and whatnot.

score 5 · Answer 2 · answered Aug 07 '13 at 09:56

5

Looks like in Rails 3.2 this just works:

# application_helper.rb
def render_my_partial
  render "my_partial"
end

answered Aug 07 '13 at 09:56

fguillen

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This also works in Rails 3.0. This looks like the best answer to me. – sockmonk Sep 12 '13 at 18:09
1

I had to use render "my_partial.html.erb" on a partial named "_my_partial.html.erb" but this worked. – Craig Wetzelberger Sep 18 '13 at 22:13
The question is specifically how to render a partial in a method on the controller exposed by the controller's `helper_method`. This doesn't address the question. – numbers1311407 Jan 09 '15 at 15:24

score -2 · Answer 3 · answered Sep 03 '11 at 04:02

-2

You could try using render_to_string method in the view helper

render_to_string :partial => test_name, :layout => false

answered Sep 03 '11 at 04:02

dexter

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render_to_string is not available in view helpers. – YWCA Hello Apr 05 '12 at 17:04
For me, this worked. render_partial "/static/partials/rightCol/_related" – Mukesh Salaria Aug 24 '21 at 15:26

Render partial from helper_method

3 Answers3