ActiveModel::Errors is used to handle validation errors on Rails objects. If you inspect an instance, it feels like a hash (to be more precise, it inherits from Hash):
errors = ActiveModel::Errors.new(Object.new)
=> {}
>>
?> errors.add(:base, "foo")
=> ["foo"]
>> errors.add(:base, "bar")
=> ["foo", "bar"]
>>
?> errors
=> {:base=>["foo", "bar"]}
If you need to hack anything with these errors, beware that it behaves in a special way. If you iterate over the errors it will decompose arrays.
For attributes with multiple errors such as :base => ["foo", "bar"] it yields once per value ("foo" and "bar" here) within the array and not per key.
>> for k,v in errors do
>> puts k
>> puts v
>> puts "--"
>> end
base
foo
--
base
bar
--
In contrast, a hash simply yields once per key giving you only the array as value.
Posted by Thomas Eisenbarth to makandra dev (2012-10-23 17:14)