class HouseBuyersController < ...
  def my_method
    # How could I get here the relevant model name, i.e. \"HouseBuyer\" ?
  end
end
             
        For namespaces working:
def resource_class
 controller_path.classify.constantize
end
                                                                        The accepted solution did not work for me as my controller and model was namespaced. Instead, I came up with the following method:
def controllers_model
  (self.class.name.split('::')[0..-2] << controller_name.classify).join('::')
end
                                                                        It's a bit of a hack, but if your model is named after your controller name then:
class HouseBuyersController < ApplicationController
  def my_method
    @model_name = self.class.name.sub("Controller", "").singularize
  end
end
... would give you "HouseBuyer" in your @model_name instance variable.
Again, this makes a huge assumption that "HouseBuyersController" only deals with "HouseBuyer" models.
This is not possible if you are using the default MVC, which your code doesn't seem to follow. Your controller seems to be a model but maybe you just got a type there. Anyway, controllers and models are fundamentally separated in Rails MVC so controllers cannot know which model they are associated with.
For example you could have a model named post. This can have a controller posts_controller or could have a controller like articles_controller. Rails only knows about models when you def the actual code in the controller such as
def index
  @posts = Post.all
  @posts = Article.all
end  
In rails standard controllers there is no way to know what the model is.
If your controller and model are in the same namespace, then what you want is
controller_path.classify
controller_path gives you the namespace; controller_name doesn't.
For example, if your controller is
Admin::RolesController
then:
controller_path.classify # "Admin::Role" # CORRECT
controller_name.classify # "Role"        # INCORRECT
                                                                        This will do it:
class HouseBuyersController < ApplicationController
  def index
    @model_name = controller_name.classify
  end
end
This is often needed when abstracting controller actions:
class HouseBuyersController < ApplicationController
  def index
    # Equivalent of @house_buyers = HouseBuyer.find(:all)
    objects = controller_name.classify.constantize.find(:all)
    instance_variable_set("@#{controller_name}", objects)
  end
end