GRASP (General Responsibility Assignment Software Patterns) is a design pattern in object-oriented software development used to assign tasks to different code modules.
GRASP provides a way to solve organizational problems and provides a common way to speak about abstract concepts. The design pattern sets responsibilities for objects and classes in object-oriented program design.
GRASP with an object-oriented design identifies its problems and solutions together as patterns.
Patterns of GRASP
Creator
• Who creates an Object? Or who should create a new instance of some class?
• Creator is a GRASP Pattern which helps to determine which class should be responsible for creating a new instance of a class
Information Expert
• Information Expert is a principle used to determine where to delegate responsibilities such as methods, computed fields, and so on.
• Expert principle says that assign those responsibilities to object for which object has the information to fulfill that responsibility.
Low Coupling
• Low coupling is an evaluation pattern that directs how to allocate responsibilities for the following benefits:
lower dependency between the classes,
change in one class having a lower impact on other classes,
Great ability to reuse.
Controller
• Deals with how to transfer request from the UI layer objects to domain layer objects.
• A controller object is a non-user interface object responsible for receiving or handling a system event.
• We can make an object as Controller, if
Object represents the overall system (facade controller)
Object represent a use case, handling a sequence of operations
High Cohesion
• High cohesion is an evaluation pattern that seeks to keep objects focused, manageable and understandable.
• High cohesion is generally used in support of low coupling.
• Benefits
– Easy to understand and maintain
– Code reuse
– Low coupling
Indirection
• Indirection pattern supports low coupling and reuses potential between two elements by assigning the mediation role between them to an intermediate object.
• Benefits: Low coupling, e.g. Facade, Adapter, Obserever.
Polymorphism
• According to the polymorphism principle, responsibility for defining the variation of behaviors according to the type is assigned to the type for which this variation happens.
• Benefits: Handling new variations will become easy.
Protected Variations
• Protected variations pattern protects elements against the diversity of other elements (objects, systems, sub-systems) by wrapping the focus of instability with an interface and using polymorphism to create a variety of implementations for this interface.
• Provides flexibility and protection from variations.
Pure Fabrication
• Pure fabrication is a class that does not represent concepts in the problem domain, specifically designed to achieve low coupling, high cohesion, and possible reuse arising (when the solution presented by the information expert pattern does not work).
• Benefits:
High cohesion,
low coupling
And can reuse this class.
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