In databases that allow such a feature, it would be keen if ActiveRecord reflected over the constraints of columns/attributes.
This way, the various validations and associations present in your table structure’s DDL SQL need not be repeated in your model classes. Of course this isn’t possible on all databases, but should be possible on most of the popular ones (ie. PostgreSQL and MySQL with InnoDB tables).
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I second this idea. I’ve been thinking about this a bit recently and it does seem a bit of pain to have to repeat yourself somewhat. The sticking point for me at the moment is the question of how you’d specify error messages for the constraints inherited from the database. Seems like you’d end up writing pretty much the same code as a validation currently contains anyway. Goynang
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On the other hand, there are quite a few constraints and restrictions imposed by table structure (i.e. the data model itself) that can easily be reflected in ActiveRecord.
One such thing is column sizes:
module ActiveRecord
module Validations
module ClassMethods
def validates_sizes
columns.each do |column|
case column.type
when :text, :string, :binary
validates_length_of column.name, :maximum => column.limit unless column.limit.nil?
end
end
end
end
end
end
One can also easily imagine:
- automatic validates_presence_of for NOT NULL fields which lack DEFAULTs
- automatic validates_associated for FOREIGN KEYS