What is OOP?

Object Oriented Programming (OOP) is a specific way to structure your code with Classes that provide more features to reuse and abstract your code.

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💡Think of it as a workflow to structure your code where everything is an object based on a template.

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You can define classes like Wall, Floor, View (Templates) then add functionality with Properties and Methods and then create multiple instances based on these classes.

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Definitions:

Property - is like a variable associated with a class. Think of parameters associated with objects.​
​Method - is like a function associated with a class. Think of actions that objects can perform.​
​Constructor - is a function that creates an instance of a class. Think of classes as blueprints that create instances.

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I won't go deep on how to write classes, but I want to explain the main concepts behind them so it's easier to deal with Revit API.

4 Pillars of OOP

When talking about OOP, you will often hear about 4 Pillars which refer to 4 main concepts:

• Encapsulation

• Inheritance

• Polymorphism

• Abstraction

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Let's break them down one by one so you understand the benefits of Object Oriented Programming.

1. Encapsulation (Keep it inside one Box)

Encapsulation means keeping related data and functions together in a single unit (a class).

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Think of a Coffeemaker as a Class🍵.

It need to store values like amount of beans, water, wattage... In a class we could store this data under Properties.

It can also create different kind of coffee using different settings. So we could write different functions and store them as Methods.

This would create a template for our CoffeeMaker.

Here is an example:

Now here is a kicker.

There can be many coffee makers(instances) based on the same blueprint(class).

And while they all can hold different data, and produce a bit different results, they are all based on the same blueprint that comes with the same functionality.

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That's exactly what classes are for. You define a blueprint for your object, you specify properties and methods, and then you can create many instances of that class that has access to same functionality.

And here is a simplified graphics of how it would look in code:

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Revit API is full of classes like Wall, Floor... And then all instances in the project are based on these classes so they share the same functionality because it's all Encapsulated in a Class.

2.Inheritance (Reuse like a Pro)

Inheritance is very important OOP concept that you need to understand for Revit API. It's used to create new classes based on other classes.

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Example #1:

For example, In Revit API many classes are based on the Element Class so they can inherit the base attributes like:

• .Id

• .Category

• .Parameters

• .GetTypeId()

• And so on...

And then, they have extra attributes on top for the class itself. So, Wall Class will have all Element attributes, and extra Wall attributes on top of that.

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Example #2: Think of views in Revit.

There are classes like ViewPlan, ViewSection... and all of them are based on the View class to get the main View functionality.

On top of that, the View Class is based on the Element Class. So, each layer in this chain will inherit properties from the previous classes.

This is the ultimate workflow to reuse your code. However, you don't need to create this complex relations in your code.

I want you to understand the concept so you find it easier to explore Revit API. You will notice that many classes share the same properties and methods inherited from the base classes.

3.Abstraction (Hide Internals)

Abstraction concept means showing only the necessary features while hiding the complex implementation.

For example if you would call wall.Flip() method you don't need to know all the complex geometry calculations happening behind the scenes.

You only need to know how to use it and what kind of results you get. The rest is handled by the class itself.

4.Poly-Morphism (One to Many)

Lastly a fancy word - polymorphism. To put it simply, this concepts allows us to use the same attribute name in classes but get different behavior.

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For example in Revit API you can use Location Property for many elements. However, you might get different results.

• Wall.Location - Will get you a LocationCurve

• Door.Location - Will get you a LocationPoint

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In this case, we can use the same property name (Location), and get different results(LocationCurve/ LocationPoint) because elements have diffrent logic.

• Wall - Line-Based

• Door - Point-Based

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In code it will look something like that:

This concept is more about working with multiple classes and preparing for the future.

In terms of Revit API, just keep in mind that sometimes there are differences to the output across classes even when you use the same Property/Method name.

But it's not so often and usually it makes a lot of sense logically.

Why OOP for Revit API?

OOP is an advanced concept that is more useful on larger code bases. Also, certain languages require you to code only using OOP structure, but in Python it's optional.

You don't need to become OOP expert and code using classes. It's much simpler to use existing classes than creating them.

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Understand the basics of OOP so you can:

• Read Revit API Documentation

• Use Revit API Classes

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And don't worry if it's a bit hard. You will learn it over time as you get more comfortable with programming in general.

It took me a while to understand why OOP can be useful. Just give it some time and it will come to you.

P.S.

Now that you understand the basics of Object-Oriented Programming, we are ready to dive into Revit API documentation and learn how to get the most out of it.

👀 Keep an eye on the next email where I will explain you everything you need to know about Revit API Documentation, especially if you are a beginner.

👋See you soon.

P.S.S

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​Click Here to learn more.