INDIRECTION DESIGN PATTERN SOFTWARE
INDIRECTION DESIGN PATTERN CODE

Let us modify an application from the factory method pattern, which draws different geometric shapes, this time including 2D or 3D, on the basis of client demand.

Client - uses the interfaces declared by the AbstractFactory and AbstractProduct classes.

Product - defines a product to be created by the corresponding ConcreteFactory it implements the AbstractProduct interface.

AbstractProduct - declares an interface for a type of product objects.

ConcreteFactory - implements operations to create concrete products.

AbstractFactory - declares an interface for operations that create abstract products.

The following classes are the participants of this pattern: The structure of factory method pattern is as shown in the figure below:įigure: Abstract Factory Pattern Structure Clients use the factory pattern to create platform objects but never create them directly. The 'factory' object has the responsibility for providing creative services for the entire platform family. This pattern provides a level of indirection that abstracts the creation of families of related or dependent objects without directly specifying their concrete classes. Provide an interface for creating families of related or dependent objects without specifying their concrete classes. The intent of this pattern, according to Design Patterns by Gamma et al, is to: Each generated factory can give the objects as per the factory method pattern.Īn abstract factory pattern is also called the Factory of Factories or Kit. In other words, this pattern has a super-factory that creates other factories This design pattern comes under the creational pattern as it provides one of the best ways to create an object. Use object composition to embed an instance of the class inside another class that provides a new interface.The abstract factory pattern has an interface that is responsible for creating a factory of related objects without explicitly specifying their classes.

INDIRECTION DESIGN PATTERN CODE

Use object composition and delegation instead.Ī class can't be modified, either because you don't have its source code or because too many other classes depend on it. Separate classes with additional levels of indirection. It's difficult to change one class without changing most or all other classes. The algorithm should be separated from the class, and moved into a class of its own.Ĭlasses are excessively dependent on each other. Often the solution is to wrap an additional layer of interface around the implementation.Ĭhanging an algorithm requires too many changes in the classes that use it, especially changes that affect the class's interface as well as its implementation. This is more often a problem in C++ with its pointers, pointer arithmetic, and relatively close access to the machine than it is in Java. Changing the implementation of the class forces change on the client class. Your code depends too closely on exactly how an object is implemented. Separate the request itself from the object and/or method that handles the request. Your code depends on specific methods in specific classes. Isolate the platform-dependent parts of your program from the platform-independent parts. #ifdef and conditional compilation only takes you so far.Įven Java's vaunted platform independence has a few weak spots. Your code depends on platform idiosyncrasies. Provide an extra level of indirection to the code that invokes the constructor. Changing the class of an object is burdensome because the name of the class is hard-coded in the client program through constructor invocations.ĭo not use constructors directly in your client classes. Your code depends on the names of classes. This table describes some of the common programming patterns, and suggested design patterns:

INDIRECTION DESIGN PATTERN SOFTWARE

Since the idea of an Iterator is fairly useful generally, it has been identified as one of many Design Patterns.ĭesign patterns are an important way of identifying frequently occurring ways in which objects interact, and they help in designing well-structured larger software systems that can be extended easily later.Īs such, they are an important part of the field of Software Engineering.

Objects as each having their own identity, filling a role in a larger system of components, and interacting with each other in particular ways. Once we absorb the ideas of object-oriented programming more fully, it becomes really fun to think about In other words, we have abstracted one particular functionality out of one class into another. Naturally handled within the original class. We have one class whose 'function' it is to traverse another class and provide some functionality (access to elements) that is not one class throwing a member of an exception class.one class containing fields of another classes type,.So far in this course, we have seen standard ways for objects of different types to interact: inheritance,

Indirection design pattern