O Guia Definitivo do Yii 1.1

specific operations by calling CWebUser::checkAccess; and we can also obtain the unique
identifier and other persistent identity information about the user.
Defining Identity Class
As mentioned above, authentication is about validating the identity of the user. A typical
Web application authentication implementation usually involves using a username and
password combination to verify a user's identity. However, it may include other methods
and different implementations may be required. To accommodate varying authentication
methods, the Yii auth framework introduces the identity class.
We define an identity class which contains the actual authentication logic. The identity
class should implement the [IUserIdentity] interface. Different identity classes can be
implemented for different authentication approaches (e.g. OpenID, LDAP, Twitter OAuth,
Facebook Connect). A good start when writing your own implementation is to extend
CUserIdentity which is a base class for the authentication approach using a username and
password.
The main work in defining an identity class is the implementation of the
[IUserIdentity::authenticate] method. This is the method used to encapsulate the main
details of the authentication approach. An identity class may also declare additional
identity information that needs to be persistent during the user session.
An Example
In the following example, we use an identity class to demonstrate using a database
approach to authentication. This is very typical of most Web applications. A user will enter
their username and password into a login form, and then we validate these credentials,
using ActiveRecord, against a user table in the database . There are actually a few things
being demonstrated in this single example:
• The implementation of the authenticate() to use the database to validate credentials.
• Overriding the CUserIdentity::getId() method to return the _id property because the
default implementation returns the username as the ID.
• Using the setState() (CBaseUserIdentity::setState) method to demonstrate storing
other information that can easily be retrieved upon subsequent requests.