Dirty Tracking

NoBrainer tracks changes on model attributes. You can access the following methods on a model instance. These methods register changes for both declared fields and dynamic attributes.

changed? returns a whether the instance changed.
changed returns an array of attribute names which have changed.
changes returns a hash of the form {attr => [old_value, new_value]}.

You have access to the following methods for each defined attribute:

attr_changed? returns a whether attr changed.
attr_change returns an array [old_value, new_value].
attr_was returns the old value of attr.

Field default value assignments (e.g. field :name, :default => 'hello') register their changes. In fact, the dirty tracking starts as soon as the model is instantiated or read from the database. Once the model is saved, the dirty tracking is reset. In some ways, the dirty tracking computes a diff from the content in the database with the in memory model instance.

When a field was not previously set, and then set to nil, NoBrainer will report changes even though the value to be read has technically not changed.

NoBrainer uses dirty tracking to do efficient model updates. Only the attributes that changed are sent to the database.