ActionScript 3.0 Design Patterns.pdf - VideoTutorials-bg.com

methods and properties to accomplish what it needs to do. The ITarget interface
could declare methods that are needed in the new context, but have no relation to
the existing class.
Key OOP Concepts in the Adapter Pattern
Comparing the advantages and disadvantages of object and class adapters enables us
to clearly understand the merits of composition versus inheritance in OO (objectoriented)
design.
Object and Class Adapters Compared
Choosing between object and class adapters depends on the context in which they
are used. Object adapters that use parameterized constructors are flexible because
the Adaptee object is passed to them. This decouples the Adaptor and Adaptee classes,
allowing instances of subclasses of Adaptee class to be passed to the adapter.
For their part, class adapters generally have less code, resulting in quicker implementation.
Because they subclass the Adaptee, they have an is-a relationship with the
Adaptee class. The Adapter class is therefore the same Type as the Adaptee, and easier
to deal with from a client standpoint. Clients need to create only one instance of the
Adapter class (as opposed to both an Adaptee and Adapter instance, in the case of
parameterized object adapters). Class adapters can also be less time-consuming to
implement if the target interface is large, because most methods will be inherited.
The decision to choose either an object or adapter class to implement an adapter
depends on many factors: flexibility required, the size of the interface, ease of implementation,
and match between the required interface and the Adaptee.
As a general rule, composition is better than inheritance because of its flexibility and
loose coupling. However, the adapter pattern shows that there can be instances
where you can save time and gain coding efficiency by using inheritance.
Example: Car Steering Adapter
Adapter patterns are commonly used when there is an existing legacy class that provides
the functionality you require, but whose interface doesn’t conform to what you
need. Let’s assume that we have a legacy class called LegacyCar, which is a car sprite
from an old game. The LegacyCar class was initially developed for use with a steering
wheel input device to provide an authentic driving experience. We will change the
interface to the LegacyCar class so that we can steer the car using different input
devices such as a keyboard and mouse.
Example: Car Steering Adapter | 185