Question

Say I have a table defined such that:

Entities has_many Images  
Images has_one Entity

I have a record in the Images table that has no value for entity_id that I would like to be the default image for any new entity.

When I use:

@entities.images.find(:all, :conditions => ['image_type = ?', 'avatar])

I would like the default record from the Images table to be returned iff there is no image for the current entity

Is this possible, and if so, how?

Thanks.

Answer 1

You can create a method for this in your Entity model (best practice is to use singular names for models.)

class Entity

  def avatar_images
    avatars = images.find(:all, :conditions => ['image_type = ?', 'avatar'])
    if avatars.empty?
      avatars = Image.find(:all, :conditions =>
        ['entity_id is null and image_type = ?', 'avatar'])
    end
    avatars
  end

end

Then just call that method in your controller to get either the avatar images belonging to the entity, or the default images if it has none.

@avatars = @entity.avatar_images

Edit:

It is probably a good idea to generalize this method to accept an image type as parameter, to make it more versatile:

class Entity

  def images_of_type(type)
    list = images.find(:all, :conditions => ['image_type = ?', type])
    if list.empty?
      list = Image.find(:all, :conditions =>
        ['entity_id is null and image_type = ?', type])
    end
    list
  end

end

Then in your controller:

@avatars = @entity.images_of_type('avatar')