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What is an object in programming?

By Rahul Awati

In object-oriented programming (OOP), an object is a reusable unit of code that can perform certain actions and interact with other objects in a program. In OOP languages, all objects have some behaviors and some state. The states are stored in fields (or variables) and the behaviors are exposed through methods. Regardless of the language, each object has a unique identity and is allocated some memory when it is instantiated, i.e., created.

What is an object in programming?

In OOP, objects are the things you think about first in designing a program. They are the units of code that are eventually derived from the process. Each object is made into a generic class of object.

An easy way to understand programming objects is with a real-world analogy.

Consider a person who has a name, is hungry, can talk and sleeps at night.

In the example here, the person is an object. Their name and the fact that they are hungry are both states. The fact that they talk with other humans and sleep at night are all behaviors. Different persons can have different states and behaviors. However, persons that share certain states and behaviors can be grouped into a class.

Objects and classes in OOP

When a program runs in the computer, it is an object that actually runs.

Objects are basic program components or entities that have the following characteristics:

• Know how to perform certain actions.
• Can interact with other program elements.
• Exist in memory.

Objects can do things and can have things done to them. For example, a function or method object can be programmed to modify the contents of a data structure or variable object.

Some of the things in programming that can be defined as objects include the following:

• Variables, which hold values that can be changed.
• Data structures, which are specialized formats used to organize and process data.
• Functions, which are named procedures that perform a defined task.
• Methods, which are programmed procedures that are defined as components of a parent class and are included in any instance of that class.

A class identifies objects with common attributes and behaviors and then groups them as a single entity. It can have data members and member functions that can all be accessed with the help of objects. When a class is declared, objects must be created to access the data from that class.

The object entity can be reused to perform certain actions. Thus, each object is an instance of a particular class or subclass with the class's own methods or procedures and data variables.

Simply put, a class in programming is like a blueprint from which individual program objects can be created. Classes are defined so that objects can share models and reuse the class definitions in their code. And an object is created based on a class to satisfy a specific purpose.

Types of objects

Objects can be categorized based on what they do or how they work. Some of the most used types of objects include the following:

• Function objects. They contain a single function and are used similarly to operating system or programming language functions.
• Immutable objects. They are not changed after their creation. Data and state of the object are fixed and are not changed by use of functions.
• Container objects. These can contain other objects.
• Factory objects. They are designed to create other objects.

These and other types of objects are based on design patterns, which represent repeatable solutions to common tasks or problems in programming. The patterns themselves are not objects but are used to develop objects that fulfill the functions of those patterns.

God objects are objects that break the rules by doing more than one thing. If you're still learning object- oriented programming, find out how to refactor the God object class antipattern.

Characteristics of an object

All individual objects possess three basic characteristics -- identity, state, and behavior -- regardless of the OOP language being used. Understanding these characteristics is crucial to knowing how objects and object-oriented logic work:

• Identity. Each object has its own object identifier and can be differentiated from all other objects. Each object's name, or identity, is unique and distinct from other objects.
• State. This refers to the properties of an object. For example, values of variables in the object contain data that can be added, changed or deleted. Object properties might change. Also, an object's state must have some value for the object to get initiated and for the properties of a class to be derived in that object.
• Behavior. Object behavior refers to the actions it can take. In other words, an object's behavior reflects its purpose. For example, one object can respond to another object to carry out software functions. Object behaviors are defined using functions (processes).object-based languages

Object-based languages support the full complement of features of object-oriented programming. These features are as follows:

• Abstraction. This feature refers to hiding implementation code that is not necessary for use by other objects. In other words, objects only reveal those operations that are relevant to other objects. This helps make it easier for developers to change or add to objects over time.
• Polymorphism. An object can mean or be used differently in different contexts. Depending on the context, with polymorphism, the form of the object can change.
• Inheritance. Inheritance means that object classes can reuse code (fields and methods) from other classes. To enable such reuse, a child class is created from a parent class. For example, relationships between objects can be assigned to create a class hierarchy, which enables developers to reuse coding logic to create families of related objects.
• Data encapsulation. This means that objects contain everything they need to function, including the object methods and any related data. With data encapsulation, the object can then make its interfaces available to other objects to enable them to use the object. Also, objects within a class can keep their state private.

Object-oriented programming has fundamentally transformed the development of complex software systems. The key components that clearly define this powerful approach are essential for any developer to understand. Read this break down of the core components of OOP.