I have an Impression model with an actions attribute that is serialized for Array.
class Impression < ActiveRecord::Base
serialize :actions, Array
end
Normal attribute updating procedure:
impression.update(some_attr: "new_value")
Normal array insertion procedure:
impression.actions << "new_value"
impression.save
Is there a way to insert a new value to an array attribute that works like the .update method, i.e. in one single expression?
No, this is not possible when using the ActiveRecord serialization feature because the serialization/deserialization must be controller by ActiveRecord and update performs a direct SQL update call on the database.
Some non-relational database (such as MongoDB) offers this feature because they are designed in order to do so. PostgreSQL provides a Hash extension you can install that would allow you to perform direct operations on the serialized field.
In all the other cases, you could potentially update the field directly, but I don't encourage you to do so. There is a potential risk to write corrupted data.
Instead, I suggest you to create a custom method that performs both the push and save. In any case, this is a good idea because you are exposing a custom API outside the model instead of coupling your model to the ActiveRecord architecture.
class Impression < ActiveRecord::Base
serialize :actions, Array
def add_action(action)
self.actions << action
self.save
end
end
The you can use
impression = ...
impression.add_action "new_value"
ruby-on-rails-4tag because the.updatesyntax is different for earlier versions (I think).updatein Rails 4 is the same ofupdate_attributesbefore, but I agree the tags makes sense here. Sorry for the change.