HasEnum

HasEnum allows you to store a set of related attributes in a single integer field and manipulate them as a hash. It is intended to fix the common pattern of

has_many :boolean_settings

but is not limited to boolean values.

Example

The plugin was developed for user privacy settings. A user may have multiple privacy settings like email, last_name, birthday, interests, etc. The value for each of these settings is either public, private, or friends. A normal flag-byte wouldn't support the tristate values, but HasEnum is flexible enough to handle any number of values (but keep in mind the maximum width of your integer field).

The syntax for the above example is:

has_enum :privacy_settings, :identifiers => [:public, :friends, :private] :attributes => [[:email, :private], [:last_name, :friends], [:birthday, :friends], [:interests, :public]]

:identifiers is the list of possible values for an attribute. :attributes is an array of tuples where the first element is the name of the attribute and the second is the default value.

The default column name would be 'privacy_settings_map', but that can be changed with :column.

Now you can use privacy_settings like a hash:

user.privacy_settings[:email]

=> :private

user.privacy_settings[:email] = :friends (but see limitations below)

=> :friends

user.privacy_settings[:email]

=> :friends

Limitations

As you would expect from a flag byte, specification order is important. Attribute order and number/order of identifiers must remain the same. Changing any of these will result in incorrect values from pre-existing maps.

Adding attributes is possible but they should only be added to the end of the list. Future versions will include a method for converting from one representation to another.

Currently, it is not possible to set an attribute directly because composed_of requires frozen objects. This will hopefully be coming soon.

Copyright (c) 2008 Grant Rodgers, released under the MIT license