i am currently digging into the rails 2.2.2 source to get a deeper understanding of some features (in particular model-validation) and a better overall insight. most of rails features are encapsulated in a separate module - as far as can see - and wired together through mixins. this makes sense and following the logic in the single modules is easy. but i am getting stuck while puzzling to see it altogether in the big picture.
some of my (hopefully correct) assumptions:
a) ActiveRecord::Validations::ClassMethods is included in ActiveRecord::Base giving each activerecord classmethods like "validates_presence_of"
b) ActiveRecord::Validations calls "alias_method_chain :save, :validation" to enable the validation feature while saving the record
so far so good - but the interaction of class- and instance methods is not clear to me. how is the activerecord instance (on which the validation will be applied) passed to the "validates_presence_of" class methods ?
following the flow of control over multiple "aliases and mixins" is not very easy, at least for me. i suggest it will relate to ActiveSupport::Callbacks, but i am absolutly not sure if this is the right direction to go further.
any help is really appreciated.
jan zimmek
