Top-notch video tutorials for Swift developers

A few episodes back we covered how to wrap a UIActivityIndicatorView to show loading progress in SwiftUI. Now in iOS 14 this is built in. In this episode we'll cover the various styles, how to hook it up to a Progress instance, and how to create your own custom progress visualizations.

iOS 14 Beta is now available and one of the new features is Lazy stacks. With a normal stack, all the layout happened at once, which meant poor performance for large lists of content, grids, etc. With Lazy stacks the views are only created when they first come on screen, greatly increasing the usefulness of stacks for large or infinite collections of content.

Anchors are a way we can refer to the absolute positioning of a view at any level in the view tree. This is useful when you want to have one view surround, underline, or point to another element in the view tree. Combined with GeometryReader, you don't need to worry about converting between coordinate systems like you do in UIKit. Anchors work much like other preferences, with some small differences. In this episode we will build a bar graph view, then use anchors to animate an indicator on the selected item in the graph.

Paging between views is something that is not yet provided by SwiftUI, but we can lean on UIViewControllerRepresentable to borrow this behavior from UIKit. Doing so we'll learn about the Coordinator design for handling events via delegates and datasources. We'll also see some of the rough edges you might run into when using this technique.

It can be cumbersome to pass values from parent to child view to configure something. For instance, setting a font for many Text views inside of a VStack. Luckily there is a .font() modifier that can do this for you. How does it work? It sets a value in the Environment using an EnvironmentKey. In this episode we will learn how to leverage the SwiftUI environment to pass values to descendent views, regardless of their depth from where it is set.

Using Preferences we can communicate data, such as the actual size of a view, to any ancestor view. By taking advantage of the reduce function required by the PreferenceKey protocol, we can combine multiple values in whatever way suits our needs. In this episode we will use this technique to size a bunch of sibling views equally by collecting the biggest width and then pushing this value down to subviews with some parent state.

In SwiftUI we use State to push values from a parent to a child. What if you want to go the other way, passing data about a child up to a parent? To do this we can leverage Preferences. In this episode we will see how to define a custom preference key, how to use an overlay with a GeometryReader to measure the size of a view, and then set a preference with the view's size. Then we'll learn how to respond to preference changes in an ancestor view.

Buttons in SwiftUI are much more flexible than UIButton in UIKit. For starters, there is no assumption that our buttons are just text or an image, they can use any view whatsoever for the content, which is called the "label". Using Button Styles we can create buttons in whatever shape or form we desire. In this episode we create three different button styles using SwiftUI to show how flexible they are and how easy they are to reuse.

With extensions we can encapsulate common layout and styling logic that can be reused across many views, however they do have limitations. In this episode we will see how we can create View Modifiers that allow you to leverage @State and other View-related behavior and apply this behavior to arbitrary views.

In UIKit we use imperative code to do things like display alerts, but in SwiftUI we have a declarative structure. In this episode we will see how this changes how we work with alerts. We'll look at two ways of showing alerts, one with a simple boolean state variable, and one with a bindable identifiable type that is passed to our alert, which we use to show a specific error message if an operation fails.

In UIKit we've often lamented the fact that there is no builtin facility to load an image with a URL, leaving developers to implement this on their own. In SwiftUI the situation is the same, however we have more flexibility to build what we need. Using a Swift package called FetchImage, we will create a reusable ImageView struct that can load our images efficiently given a URL.

With SwiftUI views we no longer have view controllers, and this can pose the question: Where does our data access and networking code live? In this episode we will load some data from a movies API in order to examine the ObservableObject protocol.

The Breathe app on watchOS has a really excellent animation. In this episode we attempt to recreate this animation in SwiftUI using offsets, rotation, and scaling, then making the animation repeat forever.

SwiftUI is really fun and easy to work with, but what if you need to work with a view that already exists? This episode covers the UIViewRepresentable protocol and we use it to provide a UIActivityIndicatorView to SwiftUI. The same approach can be used to wrap your own custom UIViews as well.

In this episode we add the ability to provide modal content from outside of the modal view. To do this we can leverage @ViewBuilder which is a type of Function Builder. This is a new Swift feature that gives SwiftUI's syntax a DSL rather than writing out vanilla Swift syntax.

In this episode we look at designing a modal card that takes advantage of ZStack, HStack, VStack and the Spacer helper.

Attaching gestures works quite a bit differently in SwiftUI than in UIKit. In this episode we will look at the @DragGesture property wrapper and how we can use gestures to update custom state that we can then use to transform our UI.

SwiftUI's declarative nature makes building UIs incredibly easy. In this episode we will build a wallet UI with cards. We will create a CardView so we can reuse it in multiple places. Then we will use transforms to alter it's size and position. Finally we will see how declarative animations work as we expand the cards apart.

Now that we've seen a taste of SwiftUI, let's dive into a real example and build an app. We'll have a first look at @State variables we can use to creating a binding between our state and our UI, and we'll run into a few puzzling errors and see how we can coax Xcode into giving us the right error message.

Back from WWDC 19 and blown away by the announcements. There's a lot to cover, but we'll start by digging into the most exciting announcement: SwiftUI. This is going to change everything...