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In rails 3, i know that i can force deletion of dependent objects on belongs_to and has_many relations using the :dependent => :delete option. However i was wondering,
what is the default behavior if i do not specify :dependent => ...
Cheers, Hajo
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dependent: :destroy Rails, when attempting to destroy an instance of the Parent, will also iteratively go through each child of the parent calling destroy on the child. The benefit of this is that any callbacks and validation on those children are given their day in the sun.
Active Record is the M in MVC - the model - which is the layer of the system responsible for representing business data and logic. Active Record facilitates the creation and use of business objects whose data requires persistent storage to a database.
The documentation says, "When no option is given, the behavior is to do nothing with the associated records when destroying a record." That is, deleting or destroying an object will not delete or destroy the objects that it belongs to or has many of.
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has_many uses the :nullify strategy, which will set the foreign to null. For has_many :through it will use delete_all.
For has_many, destroy will always call the destroy method of the record(s) being removed so that callbacks are run. However delete will either do the deletion according to the strategy specified by the :dependent option, or if no :dependent option is given, then it will follow the default strategy. The default strategy is :nullify (set the foreign keys to nil), except for has_many :through, where the default strategy is delete_all (delete the join records, without running their callbacks).
-- ActiveRecord::Associations::ClassMethods
Not sure exactly what belongs_to does, and wasn't able to find anything in the docs. I'll try to do some digging soon and update the answer.
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