Classifying patterns

The book by GoF on design patterns spoke about 23 design patterns and classified them under three main categories:

• Creational patterns
• Structural patterns
• Behavioral patterns

The classification of patterns is done based primarily on how the objects get created, how classes and objects are structured in a software application, and also covers the way objects interact among themselves. Let's talk about each of the categories in detail in this section.

Creational patterns:

The following are the properties of Creational patterns:

• They work on the basis of how objects can be created
• They isolate the details of object creation
• Code is independent of the type of object to be created

An example of a creational pattern is the Singleton pattern.

Structural patterns

The following are the properties of Structural patterns:

• They design the structure of objects and classes so that they can compose to achieve larger results
• The focus is on simplifying the structure and identifying the relationship between classes and objects
• They focus on class inheritance and composition

An example of a behavior pattern is the Adapter pattern.

Behavioral patterns

The following are the properties of Behavioral patterns:

• They are concerned with the interaction among objects and responsibility of objects
• Objects should be able to interact and still be loosely coupled

An example of a behavioral pattern is the Observer pattern.