100-days-of-swiftui-and-combine/day-036

Day 36: Project 7: iExpense (Part One)

Follow along at https://www.hackingwithswift.com/100/swiftui/36.

📒 Field Notes

This day covers Part One of Project 7: iExpense in the 100 Days of SwiftUI Challenge.

It focuses on several specific topics:

• iExpense: Introduction
• Why @State only works with structs
• Sharing SwiftUI state with @ObservedObject
• Showing and hiding views
• Deleting items using onDelete()
• Storing user settings with UserDefaults
• Archiving Swift objects with Codable

iExpense: Introduction

It's an expense tracker. Reign in your spending... buy Bitcoin... financial responsibility, people 😀.

Why @State only works with structs

Super short version: Structs allow us to leverage value semantics for most of our code -- and @State is meant as helper for updating to changes within to that paradigm.

Sharing SwiftUI state with @ObservedObject

https://twitter.com/cypher_poet/status/1186121232800014338

Showing and hiding views

SwiftUI's modal presentation is flow is really starting to grow on me. As straightforward as showing a modal is, thought (using the .sheet modifier), dismissal is a bit less so. Fortunately, the @Environment has our back -- allowing us to trigger dismissal from within a modal view like so:

struct MyView: View {
    @Environment(\.presentationMode) var presentationMode

    var body: some View {
      Button("Dismiss") {
          self.presentationMode.wrappedValue.dismiss()
      }
    }
}

Deleting items using onDelete()

Step 1: The view hierarchy:

List {
    ForEach {

    }
    .onDelete(perform: removeRows)
}
.navigationBarItems(leading: EditButton())

Step 2: The callback:

func removeRows(at offsets: IndexSet) {
    numbers.remove(atOffsets: offsets)
}