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What is abstraction?

From: Foundations of Programming: Object-Oriented Design

Video: What is abstraction?

So, there are four fundamental ideas in Object-Oriented Programming, four things to keep in mind when creating classes, and they have the wonderful terms Abstraction, Polymorphism, Inheritance, and Encapsulation. And one way to remember these is with the acronym APIE. Now, these terms can sound intimidating, but you do most of them already in daily thought and conversation even if you don't use these actual words. Let me prove that with the first one, Abstraction.

What is abstraction?

So, there are four fundamental ideas in Object-Oriented Programming, four things to keep in mind when creating classes, and they have the wonderful terms Abstraction, Polymorphism, Inheritance, and Encapsulation. And one way to remember these is with the acronym APIE. Now, these terms can sound intimidating, but you do most of them already in daily thought and conversation even if you don't use these actual words. Let me prove that with the first one, Abstraction.

If I say table, you know what I mean. I didn't say if I was thinking of a wooden table or a glass-topped table, if it had four legs or one central pillar, if it was large or if it was small. You might have an image in mind, that's okay. But I don't have to get that specific because you understand the idea of a table, the abstraction of a table. You've seen and experienced enough real tables to abstract the idea of what a table means.

Abstraction means we focus on the essential qualities of something rather than one specific example. An abstraction means that we automatically will discard what's unimportant or irrelevant. So your mental model of a table might have a potential height and width, but it's unlikely to have an engine size or flavor because those things are irrelevant to the idea of a table. So, abstraction means that we can have an idea or a concept that is completely separate from any specific instance.

It's what we do all the time in conversation, and it's at the heart of Object-Oriented Programming because it's what we're doing when we make a class. Abstraction means that we don't create one class for Joe's bank account and a separate class for Alice's bank account. We will focus on the essential qualities of the idea, and we will write one bank account class. We will focus on things like each of these will have an account number, each of these will have a balance.

And because we always want to discard what's unimportant, it's never just what does a bank account class look like? It's what should a bank account class look like for this application under these circumstances at this time, focusing always just on the essentials. So it might be true that every bank account was opened on a specific date, but if our application doesn't care about that piece of information, we don't need that attribute defined in our class.

But as we'll see, it's abstraction that is the foundation that supports other fundamentals of Object Orientation, such as Inheritance and Polymorphism.

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Foundations of Programming: Object-Oriented Design

47 video lessons · 49530 viewers

Simon Allardice
Author

 
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  1. 11m 35s
    1. Welcome
      1m 25s
    2. Who this course is for
      1m 15s
    3. What to expect from this course
      3m 6s
    4. Exploring object-oriented analysis, design, and development
      1m 41s
    5. Reviewing software development methodologies
      4m 8s
  2. 26m 14s
    1. Why we use object-orientation
      2m 42s
    2. What is an object?
      5m 22s
    3. What is a class?
      4m 43s
    4. What is abstraction?
      2m 45s
    5. What is encapsulation?
      3m 45s
    6. What is inheritance?
      3m 35s
    7. What is polymorphism?
      3m 22s
  3. 12m 16s
    1. Understanding the object-oriented analysis and design processes
      4m 13s
    2. Defining requirements
      6m 9s
    3. Introduction to the Unified Modeling Language (UML)
      1m 54s
  4. 23m 35s
    1. Understanding use cases
      6m 11s
    2. Identifying the actors
      4m 16s
    3. Identifying the scenarios
      5m 7s
    4. Diagramming use cases
      4m 18s
    5. Employing user stories
      3m 43s
  5. 16m 36s
    1. Creating a conceptual model
      1m 59s
    2. Identifying the classes
      2m 27s
    3. Identifying class relationships
      2m 38s
    4. Identifying class responsibilities
      6m 43s
    5. Using CRC cards
      2m 49s
  6. 22m 25s
    1. Creating class diagrams
      6m 11s
    2. Converting class diagrams to code
      4m 57s
    3. Exploring object lifetime
      5m 55s
    4. Using static or shared members
      5m 22s
  7. 19m 49s
    1. Identifying inheritance situations
      6m 49s
    2. Using inheritance
      2m 43s
    3. Using abstract classes
      2m 2s
    4. Using interfaces
      4m 20s
    5. Using aggregation and composition
      3m 55s
  8. 9m 23s
    1. Creating sequence diagrams
      5m 18s
    2. Working with advanced UML diagrams
      2m 3s
    3. Using UML tools
      2m 2s
  9. 10m 39s
    1. Introduction to design patterns
      2m 40s
    2. Example: the singleton pattern
      4m 53s
    3. Example: the memento pattern
      3m 6s
  10. 21m 47s
    1. Introduction to object-oriented design principles
      2m 50s
    2. Exploring general development principles
      3m 55s
    3. Introduction to SOLID principles
      6m 43s
    4. Introduction to GRASP principles
      8m 19s
  11. 7m 1s
    1. Reviewing feature support across different object-oriented languages
      3m 50s
    2. Additional resources
      2m 27s
    3. Goodbye
      44s

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