preferences adds support for easily creating custom preferences for models.
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git://github.com/pluginaweek/preferences.git
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Preferences for models within an application, such as for users, is a pretty common idiom. Although the rule of thumb is to keep the number of preferences available to a minimum, sometimes it’s necessary if you want users to be able to disable things like e-mail notifications.
Generally, basic preferences can be accomplished through simple designs, such as additional columns or a bit vector described and implemented by preference_fu. However, as you find the need for non-binary preferences and the number of preferences becomes unmanageable as individual columns in the database, the next step is often to create a separate “preferences” table. This is where the preferences plugin comes in.
preferences encapsulates this design by exposing preferences using simple attribute accessors on the model, hiding the fact that preferences are stored in a separate table and making it dead-simple to define and manage preferences.
preferences requires an additional database table to work. You can generate a migration for this table like so:
script/generate preferences
Then simply migrate your database:
rake db:migrate
To define the preferences for a model, you can do so right within the model:
class User < ActiveRecord::Base preference :hot_salsa preference :dark_chocolate, :default => true preference :color, :string preference :favorite_number preference :language, :string, :default => 'English', :group_defaults => {:chat => 'Spanish'} end
In the above model, 5 preferences have been defined:
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hot_salsa
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dark_chocolate
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color
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favorite_number
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language
For each preference, a data type and default value can be specified. If no data type is given, it’s assumed to be a boolean value. If no default value is given, the default is assumed to be nil.
Once preferences have been defined for a model, they can be accessed either using the accessor methods that are generated for each preference or the generic methods that are not specific to a particular preference.
There are several shortcut methods that are generated for each preference defined on a model. These reflect the same set of methods (attribute accessors) that are generated for a model’s columns. Examples of these are shown below:
Query methods:
user.prefers_hot_salsa? # => false user.preferred_language? # => true
Reader methods:
user.prefers_hot_salsa # => false user.preferred_language # => "English"
Writer methods:
user.prefers_hot_salsa = false # => false user.preferred_language = 'English' # => "English"
Each preference accessor is essentially a wrapper for the various generic methods shown below:
Query method:
user.prefers?(:hot_salsa) # => false user.preferred?(:language) # => true
Reader method:
user.prefers(:hot_salsa) # => false user.preferred(:language) # => "English"
Write method:
user.write_preference(:hot_salsa, false) # => false user.write_preference(:language, "English") # => "English"
To get the collection of all custom, stored preferences for a particular record, you can access the stored_preferences has_many association which is automatically generated:
user.stored_preferences
In addition to this, you can get a hash of all stored preferences and default preferences, by accessing the preferences helper:
user.preferences # => {"language"=>"English", "color"=>nil}
This hash will contain the value for every preference that has been defined for the model, whether that’s the default value or one that has been previously stored.
A short-hand alternative for preferences is also available:
user.prefs # => {"language"=>"English", "color"=>nil}
In addition to defining generic preferences for the owning record, you can also group preferences by ActiveRecord objects or arbitrary names. This is best shown through an example:
user = User.find(:first) car = Car.find(:first) user.preferred_color = 'red', car # user.write_preference(:color, 'red', car) # The generic way
This will create a color preference of “red” for the given car. In this way, you can have “color” preferences for different records.
To access the preference for a particular record, you can use the same accessor methods as before:
user.preferred_color(car) # user.preferred(:color, car) # The generic way
In addition to grouping preferences for a particular record, you can also group preferences by name. For example,
user = User.find(:first) user.preferred_color = 'red', :automobiles user.preferred_color = 'tan', :clothing user.preferred_color(:automobiles) # => "red" user.preferred_color(:clothing) # => "tan" user.preferences(:automobiles) # => {"color"=>"red"}
Note that preferences are not saved until the owning record is saved. Preferences are treated in a similar fashion to attributes. For example,
user = user.find(:first) user.attributes = {:prefers_hot_salsa => false, :preferred_color => 'red'} user.save!
Preferences are stored in a separate table called “preferences”.
Similar to ActiveRecord attributes, unsaved changes to preferences can be tracked. For example,
user.preferred_language # => "English" user.preferred_language_changed? # => false user.preferred_language = 'Spanish' user.preferred_language_changed? # => true user.preferred_language_was # => "English" user.preferred_language_change # => ["English", "Spanish"] user.reset_preferred_language! user.preferred_language # => "English"
Assigning the same value leaves the preference unchanged:
user.preferred_language # => "English" user.preferred_language = 'English' user.preferred_language_changed? # => false user.preferred_language_change # => nil
Before you can run any tests, the following gem must be installed:
To run against a specific version of Rails:
rake test RAILS_FRAMEWORK_ROOT=/path/to/rails
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Rails 2.3 or later