Q and A

Here are some questions that interviewers may ask to test your basic knowledge of object oriented design principles.

What is a...

1. Class:

   • A class is a fundamental building block in object-oriented programming.
   • It serves as a blueprint for defining objects in software, containing properties and methods.
   • OOP allows for one class to inherit from another, facilitating code reuse.

2. Properties and Methods:

   • Properties are the attributes (nouns) of a class, defining characteristics like color, size, etc.
   • Methods are the behaviors (verbs) of a class, defining actions like fly(), eat(), etc.

3. Inheritance:

   • Inheritance allows a child class to use the methods and properties of a parent class.
   • Child classes inherit behavior from parent classes, facilitating code reuse and promoting a hierarchical structure.
   • For example, a Bird class may inherit methods like eat() and sleep() from a parent Animal class, as birds are a type of animal.

     • Hierarchy Building:

       • Inheritance allows for the creation of a hierarchy of classes, mirroring real-world relationships.
       • It simulates how objects relate to each other through an IS A relationship.

     • Understanding IS A Relationship:

       • The goal of inheritance is not just to inherit methods but to adhere to the IS A relationship rule.
       • It ensures that subclasses represent specialized versions of their superclass and are related in a meaningful way.

     • Avoiding Poor Design:

       • Inheritance should not be used indiscriminately for method reuse.
       • For example, a Bird class should not inherit from a Vehicle class solely to use the move() method. This violates the IS A relationship principle and leads to poor design.

     • Key Principle:

       • The IS A relationship is crucial for forming class hierarchies and ensuring proper code reuse where it makes sense.
       • Well-designed applications leverage inheritance to promote code reuse in a meaningful and logical manner.

4. Public vs. Private Methods/Properties:

   • Public methods and properties are accessible from external classes, while private methods and properties are only accessible within the class itself.
   • Private members cannot be inherited by child classes.
   • Inner nested classes within the same class definition have access to private members.

5. Class Constructor:

   • A constructor is a method used to instantiate an instance of a class.
   • It typically has the same name as the class and initializes specific properties.
   • Overloaded constructors allow for multiple constructor definitions with different parameters.

6. Overloaded Methods:

   • Overloaded methods have the same name but a different set of parameters.
   • The order of parameters matters, and parameters must have different data types to avoid compilation errors.

7. Abstract Class:

   • An abstract class cannot be instantiated but can be inherited.
   • It contains abstract methods that must be implemented by its child classes.
   • Abstract methods are declared without implementation and must be implemented by subclasses.

8. Instantiation:

   • Instantiation refers to the creation of an instance (object) of a class.
   • It occurs when the class constructor method is called, providing the object with properties and methods defined in the class blueprint.

9. Passing Parameters:

   • Passing parameters by value allows methods to access only the parameter's value, not the variable itself.
   • Passing parameters by reference passes a pointer to the variable, allowing methods to modify the original variable.

10. Method Overriding:

    • Method overriding occurs when a subclass provides its own implementation for a method inherited from a superclass.
    • It allows for customizing the behavior of inherited methods in child classes.

11. Exception Handling:

    • Exception handling is a process used to handle errors that occur during program execution.
    • It allows for graceful error handling, preventing the application from crashing and providing users with feedback on how to proceed.

12. "self" Object:

    • The "self" reference refers to the current instance of the object within a class.
    • It is used to access instance variables and methods within the class.

13. Static Methods:

    • Static methods exist independently of class instances and do not have access to instance variables.
    • They are useful for defining utility functions that do not require access to instance-specific data.

When to use functional vs object oriented solutions?

• Functions are action based, and classes are state based
• Functions easier to write unit tests
• object oriented solution is better for real world simulation, or needing to keep states

What are dunder methods?