to_partial_path

Passing an active record instance to the render will look for a partial of the active record's name. This is because the active record implements to_partial_path.

This can be mimic'd by a non-active record object like so.

class Fruit
  def to_partial_path
    "fruit"
  end
end

Passing Fruit.new to render like so:

render Fruit.new

Will look for a partial name _fruit.html.erb