Change a instance method to a has_many on Rails - ruby-on-rails

Question

has_many.rb
has_many :child_attendances, -> (attendance) {
includes(:activity).references(:activity).
where(activities: {parent_activity_id: attendance.activity_id}).
where(
Attendance.arel_table.grouping(
Attendance.arel_table[:attendant_id].eq(attendance.attendant_id).
and(Attendance.arel_table[:attendant_type].eq(attendance.attendant_type))
).
or(Attendance.arel_table[:tag_code].eq(attendance.tag_code))
)
}, class_name: 'Attendance', dependent: :destroy
methods.rb
def self.child_attendances(attendance)
includes(:activity).references(:activity).
where(activities: {parent_activity_id: attendance.activity_id}).
where(
Attendance.arel_table.grouping(
Attendance.arel_table[:attendant_id].eq(attendance.attendant_id).
and(Attendance.arel_table[:attendant_type].eq(attendance.attendant_type))
).
or(Attendance.arel_table[:tag_code].eq(attendance.tag_code))
)
end
def child_attendances
self.class.child_attendances(self)
end
When using has_many.rb
-- attendance.child_attendances.to_sql
SELECT "attendances"."id" AS t0_r0 FROM "attendances" LEFT OUTER JOIN "activities" ON "activities"."id" = "attendances"."activity_id" WHERE "activities"."parent_activity_id" = 654 AND (("attendances"."attendant_id" IS NULL AND "attendances"."attendant_type" IS NULL) OR "attendances"."tag_code" = '123456789') AND "attendances"."attendance_id" = 164513
It appends "attendances"."attendance_id" = 164513, and attendance_id is not a valid column for Attendance.
When using methods.rb
-- attendance.child_attendances.to_sql
SELECT "attendances"."id" AS t0_r0 FROM "attendances" LEFT OUTER JOIN "activities" ON "activities"."id" = "attendances"."activity_id" WHERE "activities"."parent_activity_id" = $1 AND (("attendances"."attendant_id" IS NULL AND "attendances"."attendant_type" IS NULL) OR "attendances"."tag_code" = '123456789') [["parent_activity_id", 654]]
How to make the other snippet into a has_many? Rails seems to always look for a primary_key and foreign_key to make the join, when using has_many.

Answer 1

According to https://stackoverflow.com/a/34444220 what I was trying to do does not make sense to be built using has_many, so I'm sticking with an instance method.
def child_attendances
self.class.includes(:activity).references(:activity).
where(activities: {parent_activity_id: activity_id}).
where(
Attendance.arel_table.grouping(
Attendance.arel_table[:attendant_id].eq(attendant_id).
and(Attendance.arel_table[:attendant_type].eq(attendant_type))
).
or(Attendance.arel_table[:tag_code].eq(tag_code))
)
end