Two ways of determining parameter

understandable_code.rb

def filter(params_or_filter)
  params = if params_or_filter.is_a?(Hash)
    params_or_filter
  else
    params_or_filter.conditions
  end
  # ...
end

def filter(params_or_filter)
  params = filter = params_or_filter
  params = filter.conditions unless params.is_a?(Hash)
  # ...
end