Private Methods

In many ways, flex_columns models its behavior after ActiveRecord — for example, automatic generation of attribute methods. However, flex_columns offers an option ActiveRecord doesn't: you can make attribute methods private by default.

This is a deliberate choice, as ActiveRecord's "everything is public" design choice makes true encapsulation very difficult — any code, anywhere in the system, can easily set any ActiveRecord column to any value at all. By allowing fields to be private, flex_columns can help ensure that access is only done via valid code paths.

If you add :visibility => :private to a particular field in a flex column, then the generated methods for that column will be marked as private. If you add :visibility => :private to the flex column itself, then all generated methods for that column will be marked as private, unless you individually mark them as public.

For example:

class User < ActiveRecord::Base
  flex_column :user_attributes do
    field :maximum_emails_per_week, :visibility => :private
    field :background_color
  end

  flex_column :more_attributes, :visibility => :private do
    field :foo
    field :bar, :visibility => :public
  end
end

my_user = User.find(...)

my_user.maximum_emails_per_week                     # NoMethodError: private method 'maximum_emails_per_week' called
my_user.user_attributes.maximum_emails_per_week     # NoMethodError: private method 'maximum_emails_per_week' called
my_user.maximum_emails_per_week = 3                 # NoMethodError: private method 'maximum_emails_per_week=' called
my_user.user_attributes.maximum_emails_per_week = 3 # NoMethodError: private method 'maximum_emails_per_week=' called
my_user.background_color                            # fine

my_user.foo                                         # NoMethodError: private method 'foo' called
my_user.foo = 3                                     # NoMethodError: private method 'foo=' called
my_user.bar                                         # fine
my_user.bar = 'some value'                          # fine

Note that if you want to use Ruby's private or public method to change the visibility of one of these methods, it's slightly tricky. So that method overriding will work properly, these methods are actually defined on a module that's included into the flex-column class and ActiveRecord class; you can't simply say private :foo, for example. Instead, you must first override the method (a simple call to super works fine), and then make that method public or private.