laevandus

struct ContentView: View {
    @ObservedObject var viewModel: ViewModel
    
    var body: some View {
        NavigationView {
            VStack {
                List(viewModel.colors, id: \.objectID) { (colorItem) in
                    Cell(colorItem: colorItem)
                }
            }.navigationBarTitle("Colors")

laevandus

extension ContentView {
    final class ViewModel: NSObject, NSFetchedResultsControllerDelegate, ObservableObject {
        private let colorController: NSFetchedResultsController<ColorItem>
        
        init(managedObjectContext: NSManagedObjectContext) {
            let sortDescriptors = [NSSortDescriptor(keyPath: \ColorItem.hex, ascending: true)]
            colorController = ColorItem.resultsController(context: managedObjectContext, sortDescriptors: sortDescriptors)
            super.init()
            colorController.delegate = self
            try? colorController.performFetch()

laevandus

final class ColorItem: NSManagedObject {
    @NSManaged var hex: String
}

laevandus

// Diffable data source (new in iOS 13)
optional func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChangeContentWith snapshot: NSDiffableDataSourceSnapshot)
optional func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChangeContentWith diff: CollectionDifference<NSManagedObjectID>)
		
// Manually updating table view and collection view
optional func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange anObject: Any, at indexPath: IndexPath?, for type: NSFetchedResultsChangeType, newIndexPath: IndexPath?)
optional func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange sectionInfo: NSFetchedResultsSectionInfo, atSectionIndex sectionIndex: Int, for type: NSFetchedResultsChangeType)
optional func controllerWillChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>)
optional func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestRes

laevandus

struct EqualWidthPreferenceKey: PreferenceKey {
    typealias Value = CGFloat
    static var defaultValue: CGFloat = 0
    
    static func reduce(value: inout CGFloat, nextValue: () -> CGFloat) {
        value = nextValue()
    }
}

struct EqualWidth: ViewModifier {

laevandus

struct ContentView: View {
    @State private var textMinWidth: CGFloat?
    
    var body: some View {
        VStack(spacing: 16) {
            TextBubble(text: "First", minTextWidth: $textMinWidth)
            TextBubble(text: "Second longer", minTextWidth: $textMinWidth)
        }
    }
}

laevandus

struct NumberTextField: View {
    init(_ title: String, value: Binding<NSNumber>, formatter: NumberFormatter) {
        self.title = title
        self.stringTransformer = StringTransformer(value, formatter: formatter)
    }
    
    private let title: String
    @ObservedObject private var stringTransformer: StringTransformer
    
    var body: some View {

laevandus

import Combine
import SwiftUI

struct FormatterView: View {
    @State var limits: TemperatureLimits
    
    var body: some View {
        VStack(spacing: 16) {
            VStack {
                Text("Low")

laevandus

struct TemperatureLimits {
    var low: Int = 5 {
        didSet {
            let high = max(self.high, low + 10)
            guard self.high != high else { return }
            self.high = high
        }
    }
    var high: Int = 30 {
        didSet {

laevandus

import CoreGraphics

extension CGRect {
    init(center: CGPoint, size: CGSize) {
        self.init(x: center.x - size.width / 2.0, y: center.y - size.height / 2.0, width: size.width, height: size.height)
    }
    
    var center: CGPoint { return CGPoint(x: midX, y: midY) }
}