Object-oriented programming (OOP) in Swift.





      Object-oriented programming (OOP) in Swift
  • Object-oriented programming (OOP) is a programming paradigm that is based on the concept of "objects", which can contain both data and behavior. The fundamental concepts of OOP are encapsulation, inheritance, and polymorphism. These concepts are collectively known as the "four pillars" of OOP and are often referred to as the OOP concepts.

  • Encapsulation: Encapsulation is the process of hiding the internal details of an object from the outside world. It is achieved by using access modifiers like "public", "private", and "protected" to control the visibility of the object's properties and methods. This allows for data hiding and data protection, and improves the security of the object.

  • encapsulation is implemented using access control levels and access modifiers. Swift provides three levels of access control: open, public, internal, fileprivate, and private.

  • Open: Classes, methods, and properties marked as open can be accessed and overridden by any module, including other frameworks and applications.

  • public: Classes, methods, and properties marked as public can be accessed and overridden by any module, including the current module and other modules.

  • internal: Classes, methods, and properties marked as internal can be accessed and overridden by any code within the same module, but not by code in other modules. This is the default access level.

  • fileprivate: Classes, methods, and properties marked as fileprivate can be accessed and overridden by any code within the same source file, but not by code in other files of the same module.

  • private: Classes, methods, and properties marked as private can only be accessed and overridden by code within the same enclosing declaration (class, struct, enum).

  • By using access control levels, we can limit the visibility of properties and methods to only those classes and structs that need to access them. This allows us to hide the implementation details of a class, struct or enum and protect the integrity of the data.

  • For example, if we want to encapsulate a property and restrict the access to it, we can mark it as private:


  • In this example, the balance property is private, which means that it can only be accessed and modified within the Account class, and not from outside the class. This ensures that the value of the balance can only be modified by the deposit and withdraw methods, and not directly by any other code.

  • Inheritance: Inheritance is the ability of a class to inherit the properties and methods of its parent class. It creates a hierarchy of classes and allows for code reuse. Subclasses can inherit the properties and methods of their parent class and can also add new properties and methods or override existing ones.

  • Polymorphism: Polymorphism is the ability of an object to take on multiple forms. It allows objects of different classes to be treated as objects of a common class. This makes it possible to write code that can work with objects of different types.

  • In Swift, polymorphism can be implemented using protocols, generics, and extensions.

  • Protocols: A protocol defines a blueprint of methods, properties, and other requirements that any class, struct or enum must conform to. A class, struct or enum that conforms to a protocol can be treated as an instance of that protocol. By using protocols, we can define an interface that can be used by any class, struct or enum that conforms to it, thus allowing for polymorphism.


  • Generics: Generics allows us to write code that can work with any type, rather than being restricted to specific types. This allows us to write flexible and reusable code that can work with multiple types. By using generics, we can write functions and classes that can work with any type, and thus exhibit polymorphic behavior.


  • Extensions: By extending a class or struct to conform to a protocol, we can add new functionality to it, while keeping the implementation details hidden. This allows us to write code that can work with objects of different types, while abstracting away the implementation details of those types.



  • Abstraction: Abstraction is the process of hiding the implementation details of an object and exposing only the required information to the outside world. It allows for a simpler and more consistent interface to be presented to the user.

  • In Swift, abstraction is implemented using protocols and abstract classes.

  • Protocols: A protocol defines a blueprint of methods, properties, and other requirements that any class, struct or enum must conform to. A class, struct or enum that conforms to a protocol can be treated as an instance of that protocol. By using protocols, we can define an interface that can be used by any class, struct or enum that conforms to it, thus abstracting away the implementation details of that class, struct or enum.


  • Abstract Classes: An abstract class is a class that cannot be instantiated, it serves only as a base class for other classes. By using abstract classes, we can define a common interface or set of properties and methods that must be implemented by subclasses. This allows us to abstract away the implementation details of the subclasses, while still ensuring that they have a certain set of functionality.




  • OOP concepts are the fundamental concepts of object-oriented programming that allow for encapsulation, inheritance, polymorphism and abstraction. These concepts enable developers to write more modular, flexible, and maintainable code.



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