Dynamically call model methods to chain includes

gistfile1.rb

## Customer.rb	

def self.references
  includes(:account)
end
	
def self.forms
  includes(:forms)
end

def self.conditionally_include
  hash = { :references => true, :locations => false, :forms => false }
  hash.inject(self) do |query, (k, v)|
    v ? query.send(k) : query
  end
end