This post contains two examples of Adapter Design Pattern using PHP. I am giving these examples in order to understand more comprehend about Adapter Pattern.
First, implementation of Adapter Design Pattern statement
Convert the interface of a class into another interface clients expect.
Adapter lets classes work together that couldn’t otherwise because of incompatible interfaces.
Adapters are helpful if you want to use a class that doesn’t have quite the exact methods you need.
Second, implementation of using legacy class and you can’t change that legacy class but you want to port its method to another needful method.
An example class ‘clsProducts’ methods can be used inside many Adapter class to returns another result.
clsProducts object instance is passed as Adapter classes constructor argument and clsProducts methods are being used inside those Adapter classes.
Abstract factory pattern is to “provide an interface for creating families of related or dependent objects without specifying their concrete classes.”
For example a drawing & printing machine can process Low and High Resolution. Both have its own resolution drivers. Those drivers referred to concrete class with draw / print function. However the client implementation code asks the factory object class (not the concrete class) for a driver instance with provides information about resolution required. So this factory object return instance of concrete class.
The factory object implements an abstract class. It can instantiates a concrete class and return to client with casted to factory’s parent which is abstract Resolution driver.
The client uses the resolution driver as abstract without being aware about their concrete implementation.
Benefit of using factory pattern is in client code implementation, new resolution can be added with just providing that new resolution info as argument. So no change in client code.
In programming languages, polymorphism means that some code or operations or objects behave differently in different contexts.
It able to process objects differently depending on their data type or class. More specifically, it is the ability to redefine methods for derived classes.
So it is overloading parent object. Child objects has all methods in their parent and childs can have more methods.
Several parent object type to support polymorphism are class, abstract and interface. In this post, I use ‘abstract’ class as parent to give polymorphism demo due to I will using it as wrapper class.
What I mean of wrapper class is I do not have to write same code over and over again in every child classes. I only have to write once in the abstract functions.
Abstract class can not have an instance or real object. It is only model of the class design but the different from ‘interface’ that abstract can have a body inside function declaration.
To explain the differences between abstract, interface and general class, look at code below: Continue reading