Class in C++

As someone who loves software engineering, I usually end up teaching beginners about difficult parts of programming. In object-oriented programming (OOP), for example in C++, a basic idea is the class. Understanding class in C++ is crucial for developing robust and scalable software systems.

In this guide, I will explain in detail about classes, their function, and the reason they are very significant in C++. Let us start learning these concepts together. Also remember to see some excellent courses at UpGrad for improving your programming abilities.

What is class in C++

A C++ class is like a plan for making objects, which are examples of the class. Think of a class as a pattern that includes data and functions together, known as the class's members. The members are very important because they decide who has characteristics (data members) and actions (member functions) the objects from this class will have. So, every object that comes from a class carries with it the attributes and methods that the class sets out, which lets you make similar kinds of objects in an effective way.

You can compare a class in C++ to a house's design plan; this class outlines the building shape and tasks, and other important features. Every house constructed following this plan has these features but works distinctly.

CPP class definition and scope

To create or define a class in C++, first you need to use the keyword ‘class’, followed by the name of your class, after that comes two curly brackets {}.

Inside these curly brackets is where you write down the parts of your class like variables and functions. The part for this class goes from the opening bracket { until the closing one }.

Here is an illustrative example:

class Car { public: int speed; // Data member void accelerate() { // Member function speed += 10; }};

In this case, Car acts as a class holding an open data member named speed and it also has a function called accelerate(). This accelerate() function changes the car's speed by making it faster. This sample demonstrates how encapsulation functions: it combines the speed information and the accelerate() method inside the Car class, making sure that everything connected with car motion is contained within this Car class.

Data members and member functions in class in C++

In class in C++, we have data members, which are variables for storing information unique to every object. Then there are member functions; they decide the ways to work with this data. These two parts mainly explain what a class can keep and perform tasks on.

Continuing with the Car class example:

• Data member - speed - It is a variable for keeping the car's speed. Every car object made from Car class may possess a different speed value.

• Member function - accelerate() - this is a method that makes the car go faster. It works with the speed data inside, showing how functions that are part of the class can change its own information.

This structure demonstrates how encapsulation is used to combine data (speed) and functionality (accelerate()) in a way that makes the Car class both comprehensive and easy to understand.

C++ class template

Moving to more advanced uses of classes, a C++ class template allows you to define a blueprint for classes that can handle multiple data types without rewriting the entire class code for each type. This feature is incredibly useful for creating generic, reusable classes.

Here’s how you can define a generic Pair class using a template:

template <typename T1, typename T2>class Pair { public: T1 first; T2 second;};

With this class template, you can create pairs of various types, like Pair<int, double> or Pair<string, string>, without needing separate classes for each type. This shows the power of templates to create flexible and type-safe data structures.

C++ generic class

A C++ generic class uses the same principles as class templates, providing a way to work with different data types while ensuring type safety and enhancing code reusability and flexibility. The use of templates and generics helps in creating classes that are not tied to specific data types, which means you can use these classes with any compatible type.

The Pair class defined above is an example of such a generic class:

template <typename T1, typename T2>class Pair { public: T1 first; T2 second;};

Here, Pair can be created with any types for T1 and T2. This makes the class flexible to use in various sections of your program or even other programs. It reduces repeating code and improves how well your code can adjust to new situations.

How to create a class in C++

To create a class in C++, follow these steps:

1. Define the class using the class keyword.
2. Add data members and member functions.
3. Create objects of the class and use them.

Why is class in cpp relevant for OOPS

In object-oriented programming, which we call OOP for short, classes are very important. Class in C++ are therefore key to making OOP ideas work right. A class is like a plan for making objects and it shows how main OOP things like wrapping data and functions together (encapsulation), creating new types from existing ones (inheritance) and letting one thing act in many forms (polymorphism).

Next, I will explain more about each part to show why classes are very important for object-oriented programming in C++.

Encapsulation: Securing the Data

A big reason why class in C++ is important is because of something called encapsulation. This is when you put together the data, like attributes, and methods, which are really functions, to work on that data inside one unit we call a class. Encapsulation makes a protective layer which stops external functions and classes from directly reaching and changing the object's internal state.

In C++, it is possible to manage who can use the parts of a class, like variables and functions, by applying access labels such as public, private or protected.

• Private members: Members in a C++ class are private by default, which means they can only be reached or changed by functions that belong to the same class. This is a straight application of encapsulation that makes sure private information stays hidden from outside functions.

• Public members: Public members, however, are accessible from outside the class. This lets objects interact while controlling which elements of a class's internal information are shown.

• Protected members: Protected members are like private ones, but derived classes can use them too; this helps with the idea of inheritance in object-oriented programming.

class Account {private: double balance; // Private member, not accessible outside the classpublic: void deposit(double amount) { if (amount > 0) { balance += amount; } } double getBalance() { return balance; // Provides controlled access to the private member }};

In the Account class, the balance is kept private to stop it from being changed directly by something outside of the class, which keeps the internal state safe.

Inheritance: Building on Existing Code

Inheritance is an important part of OOP that a c plus plus class uses. It lets one class come from another, known as the base class. This means the new derived class gets to have all the things from the base class that are not private. Reusing the existing code helps to arrange features into groups and cuts down on repeating the same code.

Here’s a C++ class example to explain the idea better:

class Vehicle { // Base class
public:
string brand = "Ford";
void honk() {
cout << "Beep, beep!" << endl;
}
};
class Car: public Vehicle { // Derived class
public:
string model = "Mustang";
void display() {
cout << "Brand: " << brand << ", Model: " << model << endl;
}
};

In this instance, the Car is a type of Vehicle which means it can use the Vehicle's brand and honk() function. Additionally, the Car has its unique model characteristic and a display() action. This shows us that classes help with inheritance by letting new items adopt properties and functions already present but also add their own features.

Polymorphism: Interacting with Objects Uniformly

Polymorphism is an idea where one single way to interact can show many different basic shapes or kinds of data. In C++, we make polymorphism happen mostly by using inheritance and functions called 'virtual'. It lets things of similar yet not the same types be handled as if they are objects of a shared type.

Polymorphism allows for writing code that is flexible and can be reused, as one function has the capability to work with objects from various classes.

class Animal {public: virtual void animalSound() { cout << "The animal makes a sound" << endl; }};class Pig : public Animal {public: void animalSound() override { cout << "The pig says: wee wee" << endl; }};class Dog : public Animal {public: void animalSound() override { cout << "The dog says: bow wow" << endl; }};

In the code above, the Animal class provides a base animalSound method, while Pig and Dog provide specific overrides for it. This use of virtual functions and method overriding is a classic example of polymorphism.

Concluding Remarks

Grasping the concept of classes in C++ is essential to excel in object-oriented programming. Classes help by keeping data and actions together, which makes the code easier to manage and use again. If you want to know more about these ideas, I suggest looking into courses at UpGrad. There you can learn additional tools, techniques, strategies, and more on software engineering and improve your coding abilities.

FAQs

1. What is a class in C++?

A C++ class acts like a plan for making objects that hold both data and functions together.

2. How do you declare a class in C++?

In C++ programming, you use the word 'class' to start making a class. Then, you write the name of th.ais class and put curly brackets after that with all its parts inside.

3. What are data members and member functions in a class?

Member variables are the parts inside a class, and member functions ar.se the operations that work on these parts.

4. What are the benefits of classes in C++?

Classes in C++ assist in making code that is modular, can be used again, and easy to manage. They also provide support for Object-Oriented Programming functions such as encapsulation, inheriting traits from other classes, and the ability of one object to take on many forms.

5. What is a class in programming with an example?

In computer coding, a class acts as a blueprint to make objects. Like, from a Car class you can create different car objects that represent diverse cars.

6. What is the scope of a class in C++?

In C++, the range of a class goes from where it starts with an opening brace to where it ends with a closing brace, and this includes all its variables and functions inside.