Call gravatar_for in Rails Model

Question

I am trying to call gravatar_for from one of my models. (Yes I realise this isn't strictly MVC, but I have a legitimate reason for doing it which I am not going into). I'm trying to include the helpers for Gravatar but I haven't been successful in finding what they are.

So far including it inside my class like so doesn't work:

class AnnotationPostedActivity < NewsfeedActivity
  include GravatarHelper::PublicMethods

Answer 1

Assuming you are using the gravatar-plugin to generate image tags, there are a few problems to overcome. Note that the gravatar_for method takes a user object as its first argument.

Mixing in GravatarHelper::PublicMethods to your AnnotationPostedActivity class gives all instances access to the method gravatar_for(user, options={}). So you would say:

alice = User.new()

alice.respond_to?(:gravatar_for)
=> true

alice.gravatar_for
ArgumentError: wrong number of arguments (0 for 1)
# (you need to supply an argument - the method got zero but was expecting one)

alice.gravatar_for(alice)
=> "<img class=\"gravatar\" alt=\"\" width=\"50\" height=\"50\" src=\"http://www.gravatar.com/avatar/70375a32ad79987b9bc00cb20f7d1c95?rating=PG&amp;size=50\" />
 # (not what we want at all)

You see, you must supply the user object as the first argument of the gravatar_for method. So what you will have to do is

1. Use another gem

One that provides a module that looks at self.email instead of requiring it as a method parameter.

2. Implement the method yourself

It's easy. And there's already ruby code to follow. You will probably need to include some of Rails' helpers in your AnnotationPostedActivity model

>> gravatar_url 'github@deanandadie.net`
NoMethodError: undefined method `h' for main:Object ....

>> require 'active_support/core_ext/string/output_safety'
=> true

>> include ERB::Util
=> Object

>> gravatar_url 'github@deanandadie.net`
=> "http://www.gravatar.com/avatar/fbaf55d6c2618cafe0a759cfe85967e0?rating=PG&size=50"

Answer 2

If this is a helper module you're trying to mix into your Model, then this is a signal that things need to be moved around a bit. Helpers are really view helpers, and should only be called from the view. If there's logic there that is also useful in the model itself, then move it to a lib. For example:

# lib/gravatar_utils.rb
module GravatarUtils
  def gravatar_for(user)
    # ...
  end
end

# app/helpers/gravatar_helper.rb
class GravatarHelper
  include GravatarUtils

  def gravatar_image_tag(user)
    url = gravatar_for(user)
    # ...
  end
end

# app/models/annotation_posted_activity.rb
class AnnotationPostedActivity < NewsfeedActivity
  include GravatarUtils
end

Of course, it's probably easier to just use something like gravatar-ultimate