Block Helpers

When we write ERB views in Rails, etc., we generally DRY up the markup using helpers or partials.

However, it's quite common to overdo the 'DRYing up'.

When you find yourself passing in optional arguments to a helper/partial such as :extra_text => 'eggs', :to_s_method => 'cheese', you know that there must be a better way.

Rails already has a great solution for forms with form-builders, using helpers which yield an object which can be used for further rendering.

This small gem generates helpers similar to the form-builders, but for the general case.

Example usage

Please note that these examples are very contrived just for brevity! These block helpers are much more useful than just printing 'Hi there Marmaduke!'

Simple case

In the helper file:

module MyHelper

  class MyBlockHelper < ActionView::BlockHelper

    def hello(name)
      "<p>Hi there #{name}!</p>"
    end

  end

end

This has generated a helper called my_block_helper. So in the view:

<% my_block_helper do |h| %>
  Here goes...
  <%= h.hello('Marmaduke') %>
  ...hooray!
<% end %>

This will generate the following:

Here goes...
<p>Hi there Marmaduke!</p>
...hooray!

Accessing other helper methods

Methods available in the parent helper are available to the block helper class. In case of name clashes, you can also access those methods via the protected object helper. In the helper:

module MyHelper

  def angry
    "I'm very angry"
  end

  class MyBlockHelper < ActionView::BlockHelper

    def angry
      content_tag :div, helper.angry
    end

  end

end

In the view:

<% my_block_helper do |h| %>
  <%= h.angry %>
<% end %>

This generates:

<div>I'm very angry</div>

Using arguments

You can pass in arguments to the helper, and these will be passed through to the class's initialize method. In the helper:

module MyHelper

  class MyBlockHelper < ActionView::BlockHelper

    def initialize(tag_type)
      @tag_type = tag_type
    end

    def hello(name)
      content_tag @tag_type, "Hi there #{name}!"
    end

  end

end

In the view:

<% my_block_helper(:span) do |h| %>
  <%= h.hello('Marmaduke') %>
<% end %>

This generates:

<span>Hi there Marmaduke!</span>

Surrounding markup

Use the display method to surround the block with markup, e.g. In the helper:

module MyHelper

  class RoundedBox < ActionView::BlockHelper

    def display(body)
      %(
        <div class="tl">
          <div class="tr">
            <div class="bl">
              <div class="br">
                #{body}
              </div>
            </div>
          </div>
        </div>
      )
    end

  end

end

In the view:

<% rounded_box do %>
  Oi oi!!!
<% end %>

This generates:

<div class="tl">
  <div class="tr">
    <div class="bl">
      <div class="br">
        Oi oi!!!
      </div>
    </div>
  </div>
</div>

Of course, you could use display for more than just surrounding markup.

Installation

To use in Rails, add to your environment.rb:

config.gem "markevans-block_helpers", :lib => "block_helpers", :source => "http://gems.github.com"

Copyright

Copyright (c) 2009 Mark Evans. See LICENSE for details.