Phlippie phlippieb

Injecting navigation behaviour into SwiftUI Views

This was a headscratcher so I'm pasting the code sample below where I got it to work.

Context

Suppose I have a view that will sit somewhere in my navigation stack, called SourceView. From the perspective of the wider application, this view has some buttons or actions that should trigger navigation to one or more other views, which we'll call TargetView1 and TargetView2.

The basic SwiftUI way of achieving this is to make SourceView aware of this navigation requirement, and implementing the navigation inside SourceView, by embedding a NavigationLink in its view hierarchy. A NavigationLink is a visible UI component akin to a button that a user can tap.

The problem

Consider two models defined like this:

struct User {
  let id: Int
  let name: String
  let email: String
}

	import Foundation

	/// Provides ergonomics for treating Swift Dates at day-specific granularity
	struct CalendarDate {
	let date: Date
	private var calendar: Calendar { .current }
	}

	// MARK: Creating instances -

	/**
	Leveraging Swift's type system to represent the concept of an index type with a fixed size,
	so that iterating over all indices doesn't require a default case.
	*/

	/// The abstract properties of a fixed-size index type
	protocol ExactNumberOfIndices: CaseIterable, RawRepresentable where RawValue == Int {}

	/// A concrete fixed-size index type with 1 element (namely 0)
	enum _1: Int, ExactNumberOfIndices {

	/*
	In anticipation of iOS 13, I'm implementing Sign in with Apple.
	To get started, I just made a simple VC that brings up the auth stuff, without even handling the result.

	When running it in a simulator and completing the sign in process, the process appears to be broken:
	- The auth controller is not dismissed
	- `ASAuthorizationController`'s delegate method `authorizationController:didCompleteWithAuthorization` is not called

	The code below is intended as a simple copy+paste to make problem replication easier:
	1. Create a new XCode project

	/*
	Given an array with optional sub-arrays, how can I flatten the array?

	Example:

	Given [[1, 2], nil, [3]]
	Expect [1, 2, 3]

	Solution:

	// Say you have a generic class with a couple of generic types,
	// that also takes a couple of parameters in its initializer:

	class Foo<T, U, V> {
	init(label: String, other: Any) {
	// ...
	}
	}

	// Instantiating objects of this class in the standard way, while not unusual,

	//
	// TableviewDatasource.swift
	//
	// Created by Phlippie Bosman on 2019/01/30.
	// Copyright © 2019 Kalido. All rights reserved.
	//

	import Reusable
	import SwiftLCS

	/// Synched operations will only run one at a time.
	/// The `operation` method is responsible for calling `complete` to notify the object when it is done.
	final class SyncedOp {
	// Use a GCD Semaphore to synchronize flag access.
	private let semaphore = DispatchSemaphore(value: 1)

	private var isBusy = false
	private var isRetriggerQueued = false

	internal var operation: () -> () = {}

	/*
	This code demonstrates a way to get UITableViewCells to resize
	after their content size has changed, without needing to reload
	the cells.

	Prerequisites:
	- The table view must be set up to calculate its cell heights dynamically; i.e.
	tableView.rowHeight = UITableView.automaticDimension
	tableView.estimatedRowHeight = 100 // or some good estimate
	- The cell must be laid out using auto layout. Remember to add the subviews to