At WWDC 2018, Craig Federighi provided a sneak peek at what everyone was calling Marzipan: an as-yet-unnamed way for iPad app developers to bring their apps to the Mac. So, it came as no surprise when Federighi retook the stage in 2019 and revealed more details about the project and its official name: Catalyst.
What caught a lot of developers off guard though was SwiftUI, a declarative approach to building user interfaces that was also announced at WWDC this year. SwiftUI, known before the conference as Amber, its rumored project name, was on developers' radar almost as long as Catalyst, but it's fair to say that few anticipated the scope of the project. The purpose of SwiftUI is to allow developers to build native user interfaces across all of Apple's hardware platforms – from the Apple Watch to the Mac – using highly-readable, declarative syntax and a single set of tools and APIs. If that weren't enough to get developers' attention, using SwiftUI carries the added advantage of providing features like dark mode, dynamic type, and localization automatically.
The message from WWDC was clear: SwiftUI is the future, a unified approach to UI development designed to simplify the process of targeting multiple hardware platforms. It's a bold, sprawling goal that will take years to refine, even if it's eagerly adopted by developers.
However, SwiftUI also raises an interesting question: what does it mean for Catalyst? If SwiftUI is the future and spans every hardware platform, why bother bringing iPad apps to the Mac with Catalyst in the first place? It's a fair question, but the answer is readily apparent from the very different goals of the two technologies.
SwiftUI serves the long-term goal of bringing UI development for all of Apple's platforms under one roof and streamlining it. It won't take over immediately though. There's still work to be done on the framework itself, which Apple will surely expand in capability over time.
By contrast, Catalyst is a shorter-term initiative designed to address two soft spots in Apple's lineup: the stagnation of the Mac app ecosystem, and the slow growth of pro iPad apps. The unstated assumption underlying the realignment seems to be that the two app platforms are stronger tied together than they are apart, which ultimately will protect the viability of their hardware too.
The impact of Catalyst on the Mac and iPad remains murky. It's still too early in the process to understand what the long-term effect will be on either platform. There's substantial execution risk that could harm the Mac or iPad, but despite some troubling signs, which I'll get to in due course, I'm convinced that Catalyst has the potential for meaningful improvements to both platforms, especially the Mac. Let's take a closer look at what those could be.