Getting to know Angular components

Model-View-Controller (MVC) is a micro-architectural pattern initially introduced for the implementation of user interfaces. As Angular developers, we use different variations of this pattern on a daily basis, most often, Model-View-ViewModel (MVVM). In MVC, we have the model, which encapsulates the business logic of our application, and the view, which is responsible for rendering the user interface, accepting user input, and delegating the user interaction logic to the controller. The view is represented as composition of components, which is formally known as the composite design pattern.

Let's take a look at the following structural diagram, which shows the composite design pattern:

Here, we have three classes:

• An abstract class called Component.
• Two concrete classes called Leaf and Composite. The Leaf class is a simple terminal component in the component tree that we will build soon.

The Component class defines an abstract operation called operation. Both Leaf and Composite inherit from the Component class, however, the Composite class also owns references to it. We can take this even further and allow Composite to own a list of references to instances of Component, as shown in the diagram. The components list inside Composite can hold references to different Composite or Leaf instances, or instances of other classes, which extend the Component class or any of its successors. We can have a different behavior of the operation methods of the individual Component instances invoked within the implementation of the operation method of Composite. This is because of the late-binding mechanism used for the implementation of polymorphism in object-oriented programming languages.