Mongoid - set a field to true for at least one document

Question

I want there always to be at least one document in database which has a field titled "selected" set to true. How do I do that? Most probably I have to use callbacks, but which one: before (or after) _create, _upsert, _update?

And how can I ensure that it will be set to true whatever operation executes: create, update, upsert...? I guess that would not be right to create a callback for each of them.

score 2 · Accepted Answer · edited May 23 '17 at 11:49

2

after_save always runs after create & update

so you could do:

after_save do |your_class|
  your_class.update_column(:selected, true) unless YourClass.where(selected: true).exists?
end

NB./ update_column should not fire the after_save again!

edited May 23 '17 at 11:49

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answered Feb 18 '13 at 13:43

gef

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will not be there an infinite recursion? – Alan Coromano Feb 18 '13 at 15:59
Good point. There's a link on that NB./ http://stackoverflow.com/questions/632742/how-can-i-avoid-running-activerecord-callbacks/7386222#7386222 – gef Feb 18 '13 at 16:09
will not be there an infinite recursion? – Alan Coromano Feb 19 '13 at 01:18

Mongoid - set a field to true for at least one document

1 Answers1