model.rb

# Works, but a bit awkward:

def self.group_by_name(r)
  r.group_by &:name
end

Model.group_by_name(models.where(..))

# Would be nicer to have

def self.group_by_name
  group_by &:name
end

Model.where(..).group_by_name # but this gives:  undefined method `group_by' for #<Class:'

I thought there was a method I could call which returns the chained relation, in the scope, on which I could call .to_a.group_by ....