Optional parameters for Rails Image Helper

Question

In my current Rails (Rails 2.3.5, Ruby 1.8.7) app, if I would like to be able to define a helper like:

  def product_image_tag(product, size=nil)
    html = '' 
    pi = product.product_images.first.filename
    pi = "products/#{pi}"
    pa = product.product_images.first.alt_text

    if pi.nil? || pi.empty?
      html = image_tag("http://placehold.it/200x200", :size => "200x200")
    else
      html = image_tag(pi, size)
    end

    html

  end

...and then call it from a view with either:

<%= product_image_tag(p) %>

...or:

<%= product_image_tag(p, :size => 20x20) %>

In other words, I'd like to be able to have this helper method take an optional size parameter. What would be the best way to go about this?

Answer 1

You're on the right track. I would do this:

def product_image_tag(product, options = {})
  options[:size] ||= "200x200"

  if img = product.product_images.first
    image_tag("products/#{img.filename}", :alt => img.alt_text, :size => options[:size])
  else
    image_tag("http://placehold.it/#{options[:size]}", :size => options[:size])
  end
end

Explanations:

Setting the final parameter to an empty hash is a common Ruby idiom, since you can call a method like product_image_tag(product, :a => '1', :b => '2', :c => '3', ...) without explicitly making the remaining arguments a hash with {}.

options[:size] ||= "200x200" sets the :size parameter to 200x200 if one wasn't passed to the method.

if img = product.product_images.first - Ruby lets you do assignment inside a condition, which is awesome. In this case, if product.product_images.first returns nil (no image), you fall back to your placehold.it link, otherwise display the first image.