ruby on rails - Make scope and instance method with same conditions more DRY -

say have model defines scope, conditions of used in instance method:

class thing < activerecord::base   scope :complete?, -> {     where(       foo: true,       bar: true,       baz: true     )   }    def complete?     foo? && bar? && baz?   end end 

if needed change definition of complete?, have remember change both scope , instance method. there nice way consolidate these 2 definitions , make code bit more dry?

the problem gets more complex if 1 of conditions instance method:

class thing < activerecord::base   scope :complete?, -> {     where(       foo: true,       bar: true,        # can't use instance method `base?` here `baz` condition       # have duplicate logic:       name: 'baz'     )   }    def baz?     name == 'baz'   end    def complete?     foo? && bar? && baz?   end end 

dry means "don't repeat yourself". in snippets don't see duplication whatsoever. there's literally nothing dry up.

what meant, though,

there 1 piece of information 2 methods generated. if information changes, how able change once, don't accidentally forget update other place?

well, can metaprogramming gymnastics such this:

class thing < activerecord::base   fields_for_complete = {     foo: true,     bar: true,     baz: true,   }    scope :complete?, -> {     where(fields_for_complete)   }    def complete?     fields_for_complete.all? |method_name, expected_value|       self.public_send(method_name) == expected_value     end   end end 

it's decide 1 easier read, understand , maintain.

me, choose first (somewhat duplicated) version. makes me think less. , it's obvious other rails programmer, might join project.