Question

Making an instance of one class a member of another class is called __________.

Short answer

Answer: Composition

Step-by-step solution

Answer

The term for making an instance of one class a member of another class is called "composition".

Key concepts

Composition

Composition in object-oriented programming is a fundamental concept where instances of one class are used as elements within another class. This is like saying that a class contains or is composed of other objects.
Consider composition as a "has-a" relationship. For example, if a "Car" class contains an instance of a "Wheel" class, we can say that a Car has-a Wheel. This is different from inheritance, which is an "is-a" relationship.

• Composition promotes flexible and reusable code.
• It helps in designing complex objects made up of smaller, manageable parts.
• It allows the creation of a new class by using existing class objects, making it easier to change parts of your program without affecting the overall structure.

In essence, composition is a great way to build complex applications with simple and independent building blocks.

Class

A class in object-oriented programming is like a blueprint or template for creating objects. It defines a set of properties and methods that the created objects will have.
Think of a class as the mold that shapes objects. For example, a "Car" class might define properties like make, model, and color, as well as methods like start and stop. These properties and methods become part of any object created from the class.

• Classes provide a way to encapsulate data and functionality together.
• They ensure that objects created are valid and consistent, as they all derive from the same blueprint.
• Using classes helps organize and structure code in a clear and logical way.

By defining classes, programmers can efficiently reuse code, leading to faster development and easier maintenance.

Instance

An instance is a concrete occurrence of any object created from a class in object-oriented programming. When you create an object from a class, you are making an instance of that class.
Every instance has its own set of data, though it follows the structure of the class it was created from. For example, you might have a "Car" class, and each car you create—say, a Toyota or a Honda—is a separate instance of the Car class.

• Instances are the actual objects created using the class template.
• Each instance can have different property values, which makes them unique.
• They allow specific interactions and storage of specific data that pertain to that particular object.

Ultimately, instances allow classes to be more than just abstract ideas, turning them into real components of an application.