CPP Abstract Class
- “CPP abstract class - one from which objects cannot be instantiated. In C++, the term abstract class is typically used to imply one that has at least one pure virtual function. Note that an object that is not instantiable for some other reason, say, having no usable constructor (other than a copy constructor), might be said to be not concrete; see also concrete class. final (1008)” (EMCppSfe 2021)
CPP abstract class is a class in CPP that cannot be instantiated on its own but serves as a blueprint for derived classes. Introduced in year 1983 with the creation of CPP, an abstract class typically contains at least one pure virtual function, which must be implemented by any derived class. This mechanism enforces a structure where the derived class is required to provide specific functionality, allowing developers to create flexible, reusable, and maintainable code. The abstract class serves as the foundation for polymorphic behavior in object-oriented design, a core principle of CPP programming.
In a typical use case, an abstract class might define a generic interface for a set of related classes that implement common behaviors. For example, in an application managing various cloud resources, the abstract class could define functions like `create()`, `delete()`, or `update()`, while the derived classes implement these functions for specific resources, such as Google Cloud virtual machines or AWS S3 buckets. By using abstract classes, developers ensure that all resource classes follow the same interface, improving code readability and reducing duplication.
CPP abstract class is particularly useful in large-scale applications, such as cloud-based systems or enterprise-level software, where defining consistent behavior across multiple components is essential. For instance, a cloud service may have a base class for all networking protocols, which could be abstract, and derived classes for HTTP, TCP, or UDP protocols would implement the specific details. This allows the system to interact with any networking protocol uniformly, facilitating flexibility and scalability. Without abstract classes, managing such diverse interactions would require redundant code, making the system more complex and difficult to maintain.
The pure virtual function is a defining feature of an abstract class. It is declared by assigning 0 to the function declaration in the abstract class. For instance, if a class has a method `virtual void connect() = 0;`, it means that the method must be implemented by any derived class. If the derived class fails to provide an implementation for this method, the compiler will generate an error. This feature ensures that the derived classes provide the necessary details for the function's behavior, maintaining the integrity of the overall system design.
One of the key advantages of using abstract class in CPP is polymorphism. By using abstract classes, developers can treat objects of different derived classes as objects of the base abstract class. This allows functions to operate on objects without needing to know their exact types. For instance, a function designed to process cloud storage resources might accept a pointer to an abstract class of resources, allowing it to handle any specific cloud resource, like Google Cloud storage or AWS EC2 instances, without altering the function itself. This capability enhances the flexibility and extensibility of applications.
Error handling and memory management in the context of abstract classes can be particularly important. When working with abstract classes, it's essential to manage memory efficiently, especially when objects are dynamically allocated. shared_ptr or unique_ptr can be used with abstract class pointers to ensure proper memory management and prevent memory leaks. When the object of a derived class is created, it is typically allocated dynamically, and using these smart pointers automatically handles the cleanup, ensuring that resources are freed when no longer needed.