module ActionView::Helpers::CaptureHelper

@greeting # => "Welcome to my shiny new web page! The date and time is 2018-09-06 11:09:16 -0500"

The return of capture is the string generated by the block. For Example:



<%= @greeting %>




You can then use that variable anywhere else. For example:

end
"The current timestamp is #{Time.now}."
@timestamp = capture do

...and Builder (RXML) templates.

<% end %>
<%= Time.now %>
Welcome to my shiny new web page! The date and time is
<% @greeting = capture do %>

The capture method can be used in ERB templates...

You can then use this object anywhere in your templates, layout, or helpers.
The capture method extracts part of a template as a String object.

def capture(*args)
  value = nil
  buffer = with_output_buffer { value = yield(*args) }
  if (string = buffer.presence || value) && string.is_a?(String)
    ERB::Util.html_escape string
  end
end

WARNING: content_for is ignored in caches. So you shouldn't use it for elements that will be fragment cached.

<% content_for :script, javascript_include_tag(:defaults) %>

Lastly, simple content can be passed as a parameter:

<%= content_for :navigation %>

Then, in another template or layout, this code would render only the last link:

<% end %>

<%= link_to 'Login', action: 'login' %>

<% content_for :navigation, flush: true do %>

<%# Add some other content, or use a different template: %>

<% end %>

<%= link_to 'Home', action: 'index' %>

<% content_for :navigation do %>

If the flush parameter is +true+ content_for replaces the blocks it is given. For example:

<%= content_for :navigation %>

Then, in another template or layout, this code would render both links in order:

<% end %>

<%= link_to 'Login', action: 'login' %>

<% content_for :navigation do %>

And in another place:

<% end %>

<%= link_to 'Home', action: 'index' %>

<% content_for :navigation do %>

identifier in order. For example:
Note that content_for concatenates (default) the blocks it is given for a particular

this technique is useful if you'll only be using these scripts in a few views.
That will place +script+ tags for your default set of JavaScript files on the page;

<% end %>
<%= javascript_include_tag :defaults %>
<% content_for :script do %>

<%= link_to 'Logout', action: 'logout', remote: true %>

Then, in another view, you could to do something like this:

<% end %>

<% content_for :script do %>

Please login!
<%# This is our view %>

creates the script identifier.
And now, we'll create a view that has a content_for call that



<%= yield %>


<%= yield :script %>



<%# This is the layout %>

yield in a layout. For example:
You can also use the yield syntax alongside an existing call to

<%= stored_content %>

This helper works just like normal helpers.

end
end
content_for(:storage) || "Your storage is empty"
def stored_content
module StorageHelper

content_for, however, can also be used in helper modules.

<%= yield :not_authorized if current_user.nil? %>

This is equivalent to:

<%= content_for :not_authorized if current_user.nil? %>

You can then use content_for :not_authorized anywhere in your templates.

<% end %>
alert('You are not authorized to do that!')
<% content_for :not_authorized do %>

yield doesn't work in helper modules, while content_for does.
Note: yield can still be used to retrieve the stored content, but calling

or the layout, you would pass the identifier as an argument to content_for.
In order to access this stored content in other templates, helper modules
Calling content_for stores a block of markup in an identifier for later use.

def content_for(name, content = nil, options = {}, &block)
  if content || block_given?
    if block_given?
      options = content if content
      content = capture(&block)
    end
    if content
      options[:flush] ? @view_flow.set(name, content) : @view_flow.append(name, content)
    end
    nil
  else
    @view_flow.get(name).presence
  end
end

<%= yield :right_col %>
<%= yield %>


<%= yield :script %>



<%# This is the layout %>

Useful to render parts of your layout differently based on what is in your views.
content_for? checks whether any content has been captured yet using content_for.

def content_for?(name)
  @view_flow.get(name).present?
end

the layout to stop looking for more contents.
template, you should use +content_for+, if not, use +provide+ to tell
concatenate several times to the same buffer when rendering a given
straight back to the layout. In other words, if you want to
The same as +content_for+ but when used with streaming flushes

def provide(name, content = nil, &block)
  content = capture(&block) if block_given?
  result = @view_flow.append!(name, content) if content
  result unless content
end

:nodoc:
Defaults to a new empty string.
Use an alternate output buffer for the duration of the block.

def with_output_buffer(buf = nil) # :nodoc:
  unless buf
    buf = ActionView::OutputBuffer.new
    if output_buffer && output_buffer.respond_to?(:encoding)
      buf.force_encoding(output_buffer.encoding)
    end
  end
  self.output_buffer, old_buffer = buf, output_buffer
  yield
  output_buffer
ensure
  self.output_buffer = old_buffer
end