associations - check satisfiability of a constraint when using rails shovel operator -

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In my rail application, I have a group class in which there are many relationships related to the question "subgroup is going to happen."

group group has_and_belongs_to_many: subgroups, class_name: 'group' ... end

I am using shovel operator group group (sub group ) As a specific group X. The hindrance in this question is that we should not make any circle when adding the subgroup, that is, I have to ensure that none of the new members is already in the ancestor of Group X.

A simple answer is to write a custom method to do this, which is definitely possible, but I want to know whether it is possible to use this False Operator and not a custom function of my own. is.

I think it is not possible to get this behavior done with a shovel operator. The good news is that the union "duck" like an array, you can use the union operator with array for converting input, for example 

  and gt; Group_a, group_b = Group.new, Group.new & gt; Group_a.subgroups | = Array (group_b)

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