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Day 49: Project 10: CupcakeCorner (Part One)

Follow along at https://www.hackingwithswift.com/100/swiftui/49.


📒 Field Notes

This day covers Part One of Project 10: CupcakeCorner in the 100 Days of SwiftUI Challenge.

It focuses on several specific topics:

  • Cupcake Corner: Introduction
  • Adding Codable conformance for @Published properties
  • Sending and receiving Codable data with URLSession and SwiftUI
  • Validating and disabling forms

Cupcake Corner: Introduction

From the description:

In this project we’re going to build a multi-screen app for ordering cupcakes. This will use a couple of forms, which are old news for you, but you’re also going to learn how to make classes conform to Codable when they have @Published properties, how to send and receive data from the internet, how to validate forms, and more.

Adding Codable conformance for @Published properties

For standard Swift objects that conform to Codable, Swift will synthesize its init(from:) function so long as all of its properties are, themselves, conformant to Codable.

This isn't the case with an ObservableObject's @Published properties, however, so if we want to make a Codable ObservableObject, we'll need to manually create a CodingKeys enum, listing all the properties we want to serialize and deserialze.

To be honest, though, I'm not so sure this is the best approach.

ObservableObjects need to be classes, and generally I prefer to use structs for models unless reference behavior and semantics are absolutely necessary. (It's almost as if it's a sign that @Published properties aren't Codable 🙂.)

In most cases, we're likely better off separating the data models of our application from observing state and responding to changes -- and as such, I've been experimenting with using ObservableObjects for view models (aka MVVM) that can be created separately for specific views. These view models, in turn, can focus on their own formatting and presentational logic -- even making use of Combine publishers and subscribers to stream updates to their @Published properties.

I tweeted about this recently -- linking a helpful blog post along the way -- and several of the projects in this repo make use of this pattern. So far, it feels pretty sweet 😀.