content_for

Allow to capture content and then render it into a different place:

content_for :assets do
  js_tag :jquery
end

# later in views
yield_content :assets
#=> '<script src="jquery.js" type="text/javascript"></script>'

Use content_for? to check whether content block exists for some key:

p content_for?(:assets)
#=> #<Proc:0x00...

p content_for?(:blah)
#=> nil

It is also possible to pass any variables into content block:

content_for :account do |name, email|
  form_tag! do
    input_tag(value: name) +
    input_tag(value: email)
  end
end

# somewhere in views
yield_content :account, :foo, 'foo@bar.com'
#=> '<form><input value="foo"><input value="foo@bar.com"></form>'

Please note that content block will be executed every time you call yield_content.

If you are using same content block multiple times on same page please consider to assign the result to a variable and use it repeatedly to avoid performance decreasing.

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capture_html

Execute given content block and return the result.

Useful when you need to display same snippet multiple times and want it rendered only once.

html = capture_html do
  js_tag(:jquery) +
  css_tag(:ui)
end

puts html
#=> <script src="jquery.js" type="text/javascript"></script>
#=> <link href="ui.css" media="all" type="text/css" rel="stylesheet">

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