Turning any project existing project into a Vision Pro app is as simple as adding Vision Pro to the Supported Destinations in your project’s settings:

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The .matchedGeometryEffect() modifier makes it possible to identify multiple views as the same view, regardless of whether they are in the same place in the view hierarchy. This is useful because you can animate a view as it changes place in the view hierarchy. The parent hierarchy is given a @Namespace and this can be passed to the modifier.

When using the modifier inside the animated views it is necessary to pass the namespace as a property so that it is accessible locally.

I am creating a grid of squares called AdaptiveView that each display their index from 0 to 99. That means that they need to be given that index, and they need to be able to alter the currently selected index. This is because each one can be tapped once to bring it into focus and again to remove it from focus.

This selectedIndex value will start as -1, which is an invalid index. This is the state where the entire grid will be shown, while tapping an AdaptiveView will change the selectedIndex to the index for that view.

The colours are a rainbow that changes based on the index. The first 7 will use each of the colours in the array, and the 8th AdaptiveView will then be red and each successive view will cycle through the colours one by one indefinitely.

Now I want to create the grid.

You may notice that each AdaptiveView is only shown in the grid only when it isn’t currently selected.

Otherwise a Rectangle will be shown, which is the primary font colour by default. In Light Mode this will be black, while in Dark Mode it will be white. The important thing is that it won’t be an AdaptiveView, and the only place an AdaptiveView with the same index will appear is in front of the grid as part of the ZStack layout. As the view in the grid is set as the source of the animation, there is no conflict in situations where both views are rendered temporarily.

Here’s how it should look:

Last tested on Xcode 15 beta 1

After my previous Daily Coding Tip, I was interested to know what the limitations of assigning a value to a property or variable.

The body in a SwiftUI view is usually a computed property, meaning it’s kinda like a function that returns the opaque type some View. If you know it’ll be the same …

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It’s now possible to use if statements and switches wherever you are assigning a value.

Unfortunately (or perhaps fortunately) this does not work when passing a parameter, for instance to create the StringProtocol inside the initialiser for a Text view.

But since I can create local variables inside the view’s body property anyway…

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Last Tested on Xcode 15.0 beta 1

When creating a Preview with the new iOS 17 #Preview macro, there is firstly an optional name. As with any optional that has a default value of nil, not adding anything is equivalent to passing nil. The default name that is displayed when a Preview has no name is unsurprisingly Preview.

Th…

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Last Tested on Xcode 15.0 beta 1

There are a number of new additions to the Charts framework, and one of them is the ability to create pie charts. This is done using SectorMark, as shown below. I am first creating an Item that will represent a single data point with a title and amount. I have made it Identifiable s…

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When I saw @Observable in the Platforms State of the Union on day 1 of WWDC, I rushed to make a tutorial that would make use of it. Instead of a model class inheriting from ObservableObject and marking its properties as @Published, we can now simply mark the model class as @Observable.

It was necessary to import SwiftData, which is a new framework that makes it easier to save data persistently. I won’t be doing that, but it isn’t possible to use @Observable if I don’t import it. I also have to import Foundation in order to access Double, which I’m using to store the width of a Rectangle in my view.

I couldn’t figure this tutorial out a week ago because @Observable isn’t compatible with @ObservedObject. This is what was previously used to access a model class that inherits from ObservableObject, and code such as $model.width can be used to access the @Published properties within that class.

Doing that now will cause an error.

Now we can actually use @State for the model, which was previously only used for local properties inside the ContentView.

This is also the first time I’ve used #Preview, which is a far easier way to show what you want in the SwiftUI Preview Canvas.

It’s difficult to print to the console using SwiftUI Previews.

There is a tab on the console called Previews, but for me it only seems to work when I run the previews on a physical device. When I’m working on the Live Preview inside Xcode, I still want to be able to print values to a console.

I’m going to be making use of LocalConsole, so make sure you go to File > Add Packages… and paste the following into the search box in the top right:

https://github.com/duraidabdul/LocalConsole

Once you’ve added the package to your project, you should be able to import it into any file.

LocalConsole displays a little console that can be dragged to one of the corners of the screen or resized, making it great for situations when the Xcode debugger isn’t connected.

I’m going to start by determining whether the app is running on Xcode’s SwiftUI Previews. It’s possible to check for an environment variable called XCODE_RUNNING_FOR_PREVIEWS, but this would still include SwiftUI Previews being run on a physical device. This is notably different from when the app is built and run on a Simulator, as that does not involve SwiftUI Previews at all.

I’m determining whether a Simulator is being used, and when it isn’t, I am returning false.

If you don’t mind LocalConsole running on a device, simply remove all lines beginning with the # symbol as well as the return false line.

Next I have my own version of the print function.

Usually it’s possible to shadow the default print function, meaning you can create a custom version of it at global scope that effectively overrides the default implementation. Unfortunately this approach does not work with SwiftUI Previews as it seems to cause an error.

Instead I removed the terminator parameter from the function, which changes the function signature enough so that it is no longer shadowing.

I’ve made it easier to access the shared instance of LocalConsole’s manager too.

Now I can create my user interface. I am going to be printing whatever is entered into a TextField when a Button is pressed. Usually I use Form, but that presents a problem with the default way LocalConsole is displayed in the top corner means it would cover up the content.

Instead I’m using a simple VStack that will centre the content.

The only other thing going on here is I’m making the console visible, but only when running on SwiftUI Previews. If you want the console to always be visible, you can simply put these lines directly in the onAppear block without using an if statement.

Last Week’s Daily Coding Tips

It’s pretty easy to access what time zones the system is aware of by accessing TimeZone.knownTimeZoneIdentifiers.

It would probably be more useful if it was an array of TimeZone values, since these have identifier as a property but can also be used in a DateFormatter. The initialiser for TimeZone that takes an identifi…

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Unix operating systems originally had a system time that was based on a number of seconds since midnight on January 1st 1970. Every Apple operating system has at its core a Unix kernel called Darwin. That’s why Date().timeIntervalSince1970 exists.

Sometimes it’s useful to be able to convert between Unix time and regular time, I’ve made a converter between the two.

There’s a NumberFormatter here that allows me to create a TextField later that can only display integers.

There’s a timeZoneOffsetString that allows me to display the hours that the local time zone is away from UTC, which confusingly stands for Coordinated Universal Time.

situating-sinologiesThe reason according to the National Institute of Standards and Technology:

In 1970, the Coordinated Universal Time system was devised by an international advisory group of technical experts within the International Telecommunication Union (ITU). The ITU felt it was best to designate a single abbreviation for use in all languages in order to minimize confusion. For example, in English the abbreviation for coordinated universal time would be CUT, while in French the abbreviation for "temps universel coordonné" would be TUC. To avoid appearing to favor any particular language, the abbreviation UTC was selected.

At the top of my Form is the TextField for the Unix time, sometimes called a timestamp.

There’s a DatePicker that is given the .environment(\.timeZone, .gmt) modifier. This changes an environment variable that sets the time zone to Greenwich Mean Time, which is “the mean solar time at the Royal Observatory in Greenwich, London, counted from midnight”. This gives an indication of where this time zone is located, but it is now more commonly referred to as the aforementioned UTC.

Although I am in the UK, this is still not the time currently being observed here.

The current UK time zone is British Summer Time, which is UTC +1.

I’ve provided another DatePicker that will display the Unix timestamp as it would be in your time zone. As British Summer Time currently adds an hour to UTC, my DatePicker is only different by one hour. Note that each DatePicker can have the same Binding<Date>, because only the UTC date has the .environment(\.timeZone, .gmt) modifier.

Go to File > Add Packages… and paste the following in the search box in the top right:

https://github.com/SFSafeSymbols/SFSafeSymbols.git

Add the package to your project, and you should be able to import the SFSafeSymbols library.

Along with being able to access SF symbols using the constants in the SFSymbol class, there is a new version of Image that takes a systemSymbol parameter instead of a systemName parameter.

Before iOS 15 there was no .foregroundStyle(_:) modifier, so it was a bit more tricky to use a gradient this way. In iOS 15 and newer versions all we have to do is pass the gradient. This is because LinearGradient conforms to the ShapeStyle protocol as well as the View protocol.

This is an app that lets you use a TextF…

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When I explored the use of implicit self after unwrapping [weak self] in Daily Coding Tip 276, it was an example of a new Swift 5.8 feature. That feature made it possible to reference functions and properties inside a closure, but only after optional binding occurs.

With [unowned self], the reference to self is not optional…

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This is a simple and free API that doesn’t require authentication.

The response contains data about a random Reddit meme from the r/memes, r/dankmemes, and r/me_irl subreddits. It is possible to get memes from a specific subreddit by adding the name of that subreddit to the end of the URL, but I will just be relying on …

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In Daily Coding Tip 217 I showed how you can use View._printChanges() to print a message in the console whenever the view refreshes.

This is an undocumented function that always does what Apple created it for: it tells you what property change occurred that resulted in the view being refreshed. There is no option to print any other information, such as what the value of the property that changed (or any other property).

The fact that the View._printChanges() function is undocumented also means that your App Store submission will be rejected from if you use it.

Instead of using that I’m creating my own function that can be put anywhere in the View body, and I can write whatever code I want to run when the view is refreshed there. The function doesn’t return anything, but in Swift every function that doesn’t return anything actually returns Void.

This is important because it explains how I can use it in the following assignment:

let _ = printRefresh()

It is now thankfully possible to create local variables inside the body. If I had simply put printRefresh() into the body, I would have got the following error:

Type '()' cannot conform to 'View'

In this case () is equivalent to Void, the return type of printRefresh() and every other function in Swift that appears to return nothing. By assigning it to the underscore _ I am effectively throwing that function result away and not storing it anywhere, whilst giving myself the ability to run the function that created it.

This is the same way that the View._printChanges() function was called in Daily Coding Tip 217.

You might be wondering what’s going on with viewHasAppeared.

I originally had my function printing “view was refreshed” even when the view was created for the first time, which doesn’t really seem like a refresh to me. To get around this I make it clear when the view has been created for the first time, which happens before the .onAppear modifier changes viewHasAppeared to true.

Last Week’s Daily Coding Tips

Type Safely

Check For Attribute Availability With hasAttribute

To quote the official Swift.org blog: Swift 5.8 also includes conditional attributes to reduce the maintenance cost of libraries that support multiple Swift tools versions. #if checks can now surround attributes on a declaration, and a new hasAttribute(AttributeName…

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3 years ago · Type Safely

Type Safely

Safely Add Parameters To a URL Using URLQueryItem

According to Wikipedia, a query string is “part of a uniform resource locator (URL) that assigns values to specified parameters”. It all begins with a question mark at the end of the base URL. After this point you can add as many parameters as you want in the format…

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3 years ago · Type Safely

Type Safely

Use hasFeature To Determine Whether Experimental Feature Flags Are Enabled

Start by creating a new Xcode project and going to your project’s Build Settings. Here you will need to use the search box in the top right to search for Swift flags, and then insert the following value: -Xfrontend -enable-experimental-concise-pound-file…

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3 years ago · Type Safely

Type Safely

Use Implicit Self After Unwrapping [weak self]

Here’s another new Swift 5.8 feature. In previous versions of the language, it was still necessary to make capture semantics specific after unwrapping [weak self]. In other words, [weak self] returns an optional version of self that you can unwrap into a non-optional version…

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3 years ago · Type Safely

Type Safely

Use Property Wrappers Like @State and @Binding Inside The View Body

I am in favour of the Swift evolution proposal Lift all limitations on variables in result builders, which was implemented in Swift 5.8. For too long it has been impossible to do all sorts of things inside a result builder. The @ViewBuilder attribute is an example of a result builder, because it can create a view even if you…

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3 years ago · Type Safely

I am in favour of the Swift evolution proposal Lift all limitations on variables in result builders, which was implemented in Swift 5.8.

For too long it has been impossible to do all sorts of things inside a result builder. The @ViewBuilder attribute is an example of a result builder, because it can create a view even if you…

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Here’s another new Swift 5.8 feature.

In previous versions of the language, it was still necessary to make capture semantics specific after unwrapping [weak self]. In other words, [weak self] returns an optional version of self that you can unwrap into a non-optional version.

When self is no longer optional, it would ma…

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Start by creating a new Xcode project and going to your project’s Build Settings.

Here you will need to use the search box in the top right to search for Swift flags, and then insert the following value:

-Xfrontend -enable-experimental-concise-pound-file

This will enable concise magic file names, a feature that is not y…

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According to Wikipedia, a query string is “part of a uniform resource locator (URL) that assigns values to specified parameters”.

It all begins with a question mark at the end of the base URL. After this point you can add as many parameters as you want in the format name=value, separating each parameter with the & symbol…

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To quote the official Swift.org blog:

Swift 5.8 also includes conditional attributes to reduce the maintenance cost of libraries that support multiple Swift tools versions. #if checks can now surround attributes on a declaration, and a new hasAttribute(AttributeName) conditional directive can be used to check whether the compiler version has support for the attribute with the name AttributeName in the current language mode

As was mentioned in the original Swift Evolution proposal, it can be a bad idea to use #if compiler(>=5.6) to check whether a feature is available. You might get the exact compiler version wrong, and the feature may not have been enabled yet.

This new method of specifying an attribute eliminates this problem, as the attribute will either be available or not.

Here’s an example of using it to check that @dynamicMemberLookup is available.

When dynamicMemberLookup is unavailable, this type and the view that uses it will not be available.

Last Week’s Daily Coding Tips

Type Safely

Add a Pressed State To a Button With a Long Press Gesture

Here’s a simple button that has three states: default, pressed and complete. My definition of ‘complete’ here is when the long press gesture has reached its minimum duration. In this case I want to wait 3 seconds before the gesture is complete. In each state I have a colour that I want the button to be. I am using two tr…

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3 years ago · Type Safely

Type Safely

Make a Random Number Generator That Works With Float, Double and Int

I want to be able to generate a random float, double, or integer within a given range. In order to do that, it helps to make NSNumber conform to the Comparable protocol. This makes it possible to decide whether one of these numbers is smaller, which will be useful later…

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3 years ago · Type Safely

Type Safely

Display More in a Table in Compact Horizontal Size Classes

I’ve noticed that the SwiftUI Table view only displays one column when the horizontal size class is compact. This happens when the iPhone is in portrait orientation, which is also the way most apps are displayed in most cases. I wanted to make it possible to display information two types of information in a single colum…

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3 years ago · Type Safely