What are the Differences Between Public, Private, and Protected Access Modifiers in Object-Oriented Programming?

Understanding the Scope of Visibility in Objects: Public, Private, and Protected

Object-oriented programming (OOP) revolves around the concept of encapsulation, which allows programmers to bundle data and behavior together into distinct units known as objects. Access to the internal components of these objects, such as functions (methods) and variables, is controlled by visibility scope. Understanding the difference between public, private, and protected access modifiers is crucial for designing robust and maintainable code.

Public

Public scope grants unrestricted access to a method or variable from any part of the program. This means that the public components of an object can be accessed from within the object itself, other objects of its own class, as well as objects from external classes. Public visibility is often used for data and operations that need to be widely accessible throughout the application.

For example, the following public method allows any object to call the doSomething() function:

public function doSomething() {
  // ...
}

Private

Private scope limits visibility to within the class where the method or variable is defined. Private components are inaccessible from outside the class, ensuring their use is restricted to the internal operations of the object. This level of encapsulation helps protect sensitive or implementation-specific data from being modified or observed by external code.

The private method in the example below can only be called from within the MyClass class:

private function doSomething() {
  // ...
}

Protected

Protected scope falls between public and private, allowing access to methods and variables within the class itself, subclasses (derived classes), and objects from the parent class. Protected visibility is typically used for components that need to be accessible to child classes while maintaining encapsulation from external code.

Protected members can be useful when implementing common functionality or data structures that should be inherited by derived classes. For instance, the following protected method can be accessed by MyClass and its subclasses:

protected function doSomething() {
  // ...
}

Choosing the appropriate scope for methods and variables in a class is essential for managing access and ensuring data integrity. Public visibility should be used sparingly and only when necessary, while private and protected visibility should be used to achieve encapsulation and modularity.

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