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# File 'lib/unpolymorph.rb', line 5
def unpolymorph( name, associations, options = {} )
scope "for_#{name}", -> obj { where( "#{obj.class.base_class.to_s.underscore}_id" => obj.id ) }
if options[:create_associations]
associations.each do |assoc|
belongs_to assoc
end
end
define_method( name ) do
var_name = "@_unpolymorph_#{name}"
value = instance_variable_get( var_name )
return value if value
associations.each do |assoc|
value = send( assoc )
if value
instance_variable_set( var_name, value )
return value
end
end
return nil
end
define_method( "#{name}=" ) do |value|
associations.each do |assoc|
if value.class.base_class.to_s.underscore == assoc.to_s
send( "#{assoc}=", value )
instance_variable_set( "@_unpolymorph_#{name}", value )
return
end
end
raise ArgumentError, "Cannot set #{name} to #{value}, no association matches"
end
define_singleton_method( "update_sql_#{name}_check" ) do |migration|
required = options.has_key?( :required ) ? options[:required] : true
constraint = required ? "exactly_one_unpolymorphic_#{name}" : "at_most_one_unpolymorphic_#{name}"
migration.execute( "ALTER TABLE #{table_name} DROP CONSTRAINT IF EXISTS #{constraint}" )
migration.execute( "ALTER TABLE #{table_name} ADD CONSTRAINT #{constraint} CHECK (#{associations.collect { |a| "(#{a}_id IS NOT NULL)::int" }.join( " + ")} #{required ? "=" : "<="} 1)" )
end
define_singleton_method( "possible_#{name}?" ) do |object|
return associations.any? { |assoc| object.class.base_class.to_s.underscore == assoc.to_s }
end
end
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