Yield and default case || do not output default case

Question

I have a simple yield use case and for some unknown reason the default case is never shown:

In my super_admin layout I have:

<%= yield :body_id || 'super_admin_main' %>

My controller

class Superadmin::GolfsController < ApplicationController
  layout "super_admin"

  def show 

  end
end

My show view

With or without

<% content_for(:body_id) do %>sadmin_golfs<% end %>

With: sadmin_golfs is shown.

without: empty string is shown instead of super_admin_main

Can anyone reproduce the same behavior ?

score 27 · Answer 1 · edited Mar 08 '11 at 22:09

27

Try <%= yield(:title).presence || 'My Default Title' %>

Object#presence is equivalent to object.present? ? object : nil (AS 3 rc docs), and essentially allows the traditional syntax with the titles.

edited Mar 08 '11 at 22:09

Andrew Grimm

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answered Aug 01 '10 at 19:00

DirectXMan12

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7

2

this is the better answer for rails 3 – cyrilchampier Oct 20 '14 at 11:16

Tatjana N. · Accepted Answer · 2010-05-26T08:53:02.443

19

Use parentheses:

<%= (yield :body_id) || 'super_admin_main' %>

Or

<%= yield(:body_id) || 'super_admin_main' %>

Without them it is assuming yield (:body_id || 'super_admin_main')

EDIT: Rails 3 uses ActiveSupport::SafeBuffer instead of string/nil (Rails 2), so the output is not nil even if there is no content_for provided. So try:

<%= yield(:body_id).empty? ? 'super_admin_main' : yield(:body_id)%>

edited May 26 '10 at 08:53

answered May 25 '10 at 18:17

Tatjana N.

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29

Actualy it stills shows an empty string when no content_for is supplied. – coulix May 26 '10 at 07:09
You do not suppy `content_for` at all or it is just blank like `<% content_for(:body_id) do %> <% end %>` ? – Tatjana N. May 26 '10 at 08:12
How about when trying to render a partial? Looking for the ability to overwrite a sidebar in specific views: `<%= yield(:sidebar).empty? ? 'special_sidebar' : yield(:sidebar) %>` – Elijah Murray Mar 12 '14 at 23:43
missed `.presence` --> `yield(:body_id).presence` – Adriano Resende Jul 16 '15 at 13:17

shingara · Answer 3 · 2010-05-26T09:51:55.423

Why no test if there are a content_for or not define in view compilation.

In the content_for code we can see :

def content_for(name, content = nil, &block)
  ivar = "@content_for_#{name}"
  content = capture(&block) if block_given?
  instance_variable_set(ivar, "#{instance_variable_get(ivar)}#{content}".html_safe)
  nil
end

So in your case, the @content_for_body_id is define if a content_for is in your view.

You can made :

<%=  instance_variable_defined?('@content_for_body_id') ? yield(:body_id) : 'super_admin_main' %>

If you prefere you can generate an helper after

def yield_or(part, result)
  instance_variable_defined?("@content_for_#{part}") ? instance_variable_get("@content_for_#{part}") : result
end

and call it in your view by

<%= yield_or(:body_id, 'super_admin_main') %>

It's works only with Rails 2.3.x

In Rails 3 :

there are this method content_for?

coulix · Answer 4 · 2010-05-26T07:53:11.603

1

In rails 3

raises undefined method `present'

edited May 26 '10 at 07:53

answered May 26 '10 at 07:29

coulix

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The most elegant solution I've found so far (without gems). Thank you. – Abdulaziz Nov 15 '13 at 10:01

score 1 · Answer 5 · edited May 23 '17 at 12:01

I know this is an old question but I have a solution for Rails 2.3.

I've extended shingara's yield_or helper method above so it can now accept a block:

module ApplicationHelper
  def yield_or(name, content = nil, &block)
    ivar = "@content_for_#{name}"

    if instance_variable_defined?(ivar)
      content = instance_variable_get(ivar)
    else
      content = block_given? ? capture(&block) : content
    end

    block_given? ? concat(content) : content
  end
end

and this can be used in your templates:

<% yield_or :something do %>
    <p>something else</p>
<% end %>

or

<%= yield_or :something, 'something else' %>

score 0 · Answer 6 · answered Mar 18 '15 at 15:16

0

<div class= <%= (yield :content_with_bunners).present? ? yield(:content_with_bunners) : "col-md-10"%>>

answered Mar 18 '15 at 15:16

stopanko

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score 0 · Answer 7 · answered Jul 21 '15 at 18:36

0

You can use content_for?(:body_id), the code will be like.

<%= content_for?(:body_id) ? yield(:body_id) : 'super_admin_main' %>

answered Jul 21 '15 at 18:36

brunodles

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Yield and default case || do not output default case

7 Answers7

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