Programming In Visual Basic Chapter 12

Object-Oriented Programming Concepts in Visual Basic

• Abstract Class: A base class intended solely for inheritance, defined with MustInherit. Cannot create instances directly; requires subclasses to override defined methods using MustOverride.

• Abstraction: Modeling of real-world entities to determine their properties and methods; aids in the planning stages of object-oriented (OO) programs by identifying needed classes.

• Abstract Method: Declared with the MustOverride keyword, serves as a placeholder for methods that must be implemented in derived classes; contains no functionality on its own.

• Accessor Methods: Provide a way to access class properties, using GET for retrieving values and SET for updating them.

• Auto-Implemented Property: Introduced in VB 2010, allows the declaration of class properties without explicitly defining GET or SET procedures; the compiler automatically generates this structure.

• Base Class: The original class, also known as the superclass or parent class, from which other classes derive.

• Child Class: The class that inherits from a base class, also referred to as a subclass or derived class.

• Class Definition: A blueprint for creating objects; defines the structure and behavior but does not create instances itself.

• Constructor: A special method invoked automatically upon instantiation of an object using NEW. Ideal for initialization tasks; must be defined in every class unless a default constructor suffices.

• Default Constructor: An implicit constructor generated by the compiler if none are defined; has no parameters.

• Destructor: Method that executes when an object is destroyed, called Finalize in VB, typically used for cleanup tasks.

• Encapsulation: Bundling of properties, methods, and events in a single unit to promote data hiding; variables should be declared as Private or Protected.

• Garbage Collection: A feature of the .NET CLR that automatically cleans up unused objects, freeing memory and resources. It activates any defined Finalize procedures.

• Inheritance: Mechanism to create new classes based on existing ones, enabling enhancements without altering the original; allows use of base class functionality in derived classes.

• Instance: A specific occurrence of a class; every object created from the class represents an instance, allowing for multiple objects based on a single class definition.

• Instance Variable: A variable specific to an instance of a class; each object maintains a separate copy, unlike shared variables.

• Instantiate: The process of creating a new object from a class; involves declaring a variable and using NEW to initialize it.

• Multitier Application: Design strategy that separates application functions across multiple layers, enhancing modularity and deployment flexibility.

• MustInherit & MustOverride: Keywords indicating that a class is abstract and cannot be instantiated directly, and methods that require overriding in derived classes, respectively.

• Object: An instantiation of a class that combines code and data, capable of generating events and possessing properties and methods.

• Overriding: A feature allowing subclass methods to have the same name as those in the base class but with distinct implementations.

• Parameterized Constructor: A constructor requiring arguments, facilitating passing parameters during object creation.

• Polymorphism: Ability of methods to operate under multiple forms; allows method calls to be made across different classes that implement the same method signatures differently.

• Property: Characteristics of class instances, can be retrieved or modified, representing attributes like flavor or topping in a cookie object.

• Property Procedure: Facilitates external access to class properties; includes methods for manipulating property values through SET and GET.

• Protected Modifier: Limits access to class elements, making them available only within that class or its subclasses.

• ReadOnly Modifier: Specifies that a property can only be read and not modified, restricting access to its GET procedure.

• Reusability: One of the primary advantages of OOP, allowing functionalities from one class to be utilized in another, enhancing code efficiency and reducing redundancy.

• Shared Variable: Declared with the Shared keyword, these variables exist for all instances of a class, unlike instance variables which are unique to each instance.

• Visual Inheritance: A feature that allows a derived form to inherit design properties from a base form, promoting consistency in UI design.

• Three-Tier Application Architecture: Divided into:

  • Presentation Tier: User interface components.
  • Business Service Tier: Validation, calculations, and business logic.
  • Data Tier: Handles data storage and retrieval.

• Steps to Override a Method: Use Overridable or MustOverride in the base class method and Overrides keyword in the derived class method.

• Object Browser: A tool for exploring classes, properties, methods, and events, useful for understanding system and user-defined classes.