example-url-opens-app

How to open an iOS app/record from an external URL and how to pass that information to a View.

About

This project demonstrates two separate concepts:

• How to use a URL to open an installed iOS application. This uses standard methods and is well documented.

• How to show a different record in a view.

• How to pass a URL's information to a sub-view. This code is tested as being reliable in its current use-case but may break if used in unintended ways. This is an alternative to using standard SwiftUI .enviroment and .onChange modifiers.

How to use this example app.

1. Open the app

2. Add multiple new records (+ icon on top left of screen). (Delete isn't implemented for MacOS/Catalyst)

3. Select a record (screen background changes color)

4. Click the Copy button

5. Paste the URL into TextEdit or Notes app (as a link)

6. Select another record (different colour, time)

7. Click the link - the app will open (if necessary) and the linked record will display with its correct time and colour. (The wrong record appears to be selected on the left -- this appears to be a well-known limit of SwiftUI -- there are complicated hacks to work around this)

Doing this in another app project.

1. Copy the following files to the project...

* UnionEvent.swift      -- A more flexible way to share data with SwiftUI than using Environment. 

* URLHelper.swift       -- Encodes and decodes URLs.

2. Copy any desired code from the following files, from the sections marked by 'AK:'...

* Application.swift     -- The `.onOpenURL() { url in ... }` modifier method which handles all incoming URL events.
                        -- The `cache` variable, which tracks event registrations.

* ContentView.swift     -- The code to switch to a new record based on changes to `selectedItem`.
                        -- The `selectedItem` variable, which is an ID matching the current record.
                        -- The `onReceivedData` modifier method and its preceding `id(..)` modifier, which receives data notifications from `onOpenURL()`, and sets `selectedItem` to show a different record.  
                        -- The `theURL(..)` methods, which create a URL from a given record's UUID -- see `Copy` button for an example.

3. Register a URL scheme in the project

• Open Project Page (project root node in the Project navigator view)

• Select Target under Targets (NOT Projects). (In this project the target is called OpenThings)

• Select the Info tab at the top.

• Expand URL Types section

• Add a URL Type (+ button). There is no delete here - to delete, go to URL Types in the project's info.plist file, then reopen the project (ancient bug workaround).

  -- Identifier: An arbitrary name of your choice -- URL Schemes: andrewkingdom.bizz.page.Examples (IMPORTANT: It is recommended to match the app's bundle ID. This is not a server address.) -- Role: Editor (or Viewer if it opens another app that you don't own) -- Icon: (unused)

4. Get a url and check that it opens the project.