ModelViewController.md

Introduction

Design Patterns that will be covered in this article:

• Model-View-Controller

Model-View-Controller

The MVC pattern simply is broken down into 3 main parts:

1. Model
   • Models hold onto application data (typically in the form of structs or simple classes)
2. View
   • Views communicate to their controller via IBActions
3. View Controller
   • Controllers coordinate between models and views

Important to Note

• Models and views should not hold strong references to their owning controller because this would cause a retain cycle
• Use the MVC design pattern as a starting point and be open to implementing other patterns as you build your app

Code

• When implementing a MVC design pattern, it's convenient to organize your app bundle's files with a Model, View, and Controller directory.

Model

• I created a simple struct that represents a single programmer

View

• I created an IBOutlet for each of the properties I have in the Programmer model

• I set the class of the default UIView element to the view I set-up programmatically (ProgrammerView).
• I dragged 3 UITextFields from our Object Library and placed it within the UIView.
• Go ahead and connect the 3 UITextFields with the IBOutlets using the Connection Inspector of the UIView.
• Make sure to set Auto Layout constraints for your UI elements.

Controller

• In your main view controller, you can hold a strong reference to the view and model that it owns.

• It's the controller's job to coordinate between the model and view.
  • In this case, the controller should update its view using the values from the model.

public var programmer: Programmer? {
  didSet {
    updateViewFromProgrammer()
  }
}

• If a programmer is set after viewDidLoad() is called, the controller should update ProgrammerView.
  • You can use a didSet to accomplish this.
• This is an example of how the model can tell the controller that something has changed and that the view needs updating.

• Conversely, this is an example of how the view can tell the controller that something has changed and the model needs updating.
• I connected the IBAction to all three of the textfields in Main.storyboard.

• To see the IBAction work with a UITextField, I connected each of the textfields to the same IBAction with an Editing Changed event.

Cautions

Not every object fits into a category of a model, view, or controller

Be-ware of the "Massive-View-Controller" or view controllers growing too big

Feel free to use other design patterns to build on top of MVC