Benefits of Object Technology
It leads to reuse, and reuse (of program components) leads to faster software development and higher-quality programs.
It leads to higher maintainability of software modules because its structure is inherently decoupled.
It leads to object-oriented system that are easier to adapt and easier to scale, ie, large systems are created by assembling reusable subsystems.
Object
It is a representation of an entity either physical, conceptual, or software.
It allows software developers to represent real-world concepts in their software design.
It is an entity with a welldefined boundary and identity that encapsulates state and behavior.
Object's State
It is one of the possible conditions that an object may exists in.
It is implemented by a set of properties called attributes, along with its values and the links it may have on other objects.
Object's Behavior
It determines how an object acts and reacts.
It is represented by the operations that the object can perform.
Object's Identity
Although two objects may share the same state (attributes and relationships), they are separate, independent objects with their own unique identity.
Four Basic Principles of Object-orientation
Abstraction
Encapsulation
Modularity
Hierarchy
Abstraction
Abstraction is a kind of representation that includes only the things that are important or interesting from a particular point of view.
It is the process of emphasizing the commonalities while removing distinctions.
It allows us to manage complexity systems by concentrating on the essential characteristics that distinguish it from all other kinds of systems.
It is domain and perspective dependent.
Sample Abstraction
An applicant submits a club membership application to the club staff.
A club staff schedules an applicant for the mock try-outs.
A coach assigns an athlete to a squad.
A squad can be a training or competing squad.
Teams are formed from a squad.
Encapsulation
Encapsulation localizes features of an entity into a single blackbox abstraction, and hides the implementation of these features behind a single interface.
It is also known as information-hiding; it allows users to use the object without knowing how the implementation fulfils the interface.
It offers two kinds of protection: it protects the object's state from being corrupted and client code from changes in the object's implementation.
Encapsulation Illustrated
● Juan de la Cruz needs to change his year level.
● The key is in the message interface.
Modularity
Modularity is the physical and logical decomposition of large and complex things into smaller and manageable components that achieve the software engineering goals.
It is about breaking up a large chunk of a system into small and manageable subsystems. The subsystems can be independently developed as long as their interactions are well understood.
Hierarchy
Any ranking or ordering of abstractions into a tree-like structure.
Kinds of Hierarchy
Aggregation
Class
Containment
Inheritance
Partition
Specialization
Type
Hierarchy Illustrated
Generalization
It is a form of association wherein one class shares the structure and/or behavior of one or more classes.
It defines a hierarchy of abstractions in which a subclass inherits from one or more superclasses.
Single Inheritance
Multiple Inheritance
It is an is a kind of relationship.
Inheritance
It is a mechanism by which more-specific elements incorporate the structure and behavior of moregeneral elements.
A class inherits attributes, operations and relationship.
Polymorphism
It is the ability to hide many different implementation behind a single interface.
It allows the same message to be handled differently by different objects.
Interface
It formalizes polymorphism. It defines polymorphism in a declarative way, unrelated to implementation.
It is the key to the plug-n-play ability of an architecture.
Aggregation
It is a special form of association that models a whole-part relationship between an aggregate (whole) and its parts.
