Stacktrace
Stacktrace is a podcast about life and technology from the perspectives of two experienced developers, John Sundell and Gui Rambo. The show explores topics such as software development, particularly Swift and iOS, along with broader industry trends and personal stories. Each episode blends technical discussion with reflections on everyday life, creating an engaging and relatable listen for developers and tech enthusiasts. The hosts share their insights and experiences in a conversational, thought-provoking format.
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209: “False positives or positive negatives”
John and Rambo discuss the pros and cons of using AI assistants and agents in the context of open source, as well as how unit testing has evolved on Apple’s platforms during the last few years, with the introduction of tools such as Swift Testing.
208: “You are the compiler”
John and Rambo discuss some of the new APIs and technologies introduced at WWDC26, including new Swift features, and changes to frameworks like AppKit and FoundationModels. Also, the state of Swift 6, and WWDC video watching strategies.
207: “It’s not magic, it’s all in the kernel”
John builds a cross-platform UI framework in Rust, and Rambo uses the macOS virtualization system to create a virtual iPhone.
206: “Let’s deprecate Xcode projects”
Using Android as an iOS user, and the state of Swift Package Manager, including how it could become a more full-featured orchestration tool for Xcode projects.
205: “The 2026 edition”
On this first episode of the 2026 season, John and Rambo discuss how they’re using AI agents when working on different projects, and how to approach learning new programming languages in 2026.
204: “Ship a prompt”
Stacktrace is back! John and Rambo check their hype levels for WWDC24, and discuss how AI might fit into Apple’s plans for this year’s releases. Also, Xcode wishes, and the challenges of building distributed systems.
203: “The Sherlock Holmes of debugging”
John and Rambo reflect on what they’ve been learning and how they’ve been aiming to improve as developers during 2023. Also, tips for getting better at debugging, deploying generative AI within existing apps, and are view models really such a good fit for SwiftUI views?
202: “Incrementing the integer”
Reactions to Apple’s “Scary fast” event, Rambo’s review of the iPhone 15 Pro Max, and under the hood of CleanupBuddy.
201: “USB-C utopia”
Will this year’s iPhones switch to USB-C instead of Lightning, what could an Apple Watch Ultra-style action button be used for on a phone, and will Apple give us another look at the Vision Pro at their upcoming “Wanderlust” event?
200: “Expectation recalibration”
Rambo’s custom implementation of macOS desktop widgets and how they relate to Apple’s new built-in system feature, why the experience of using SwiftUI depends so much on the environment it’s being used in, and a mini-review of the ASUS ROG Ally.
199: “Taking the cover off the API”
John and Rambo start diving into the new announcements from WWDC23 — including the Apple Vision Pro and visionOS, the new Apple Silicon-powered Mac Pro, as well as many of the updates to Apple’s various operating systems.
198: “WWDC23 Keynote Poker”
With the start of WWDC23 just around the corner, John and Rambo share their predictions, hopes, and dreams as to what Apple might introduce during this year’s edition of the conference. It’s Keynote Poker time!
197: “Perceived fluidity”
Reducing UI flickering, designing in-app purchase and signup flows, and how adding delays can interestingly make a UI feel more smooth and stable.
196: “That new Mac smell”
Integrating AI-powered features into an iOS app, using high refresh rate monitors with a Mac, the advantages of simple abstractions, and how the M1 and M2 Max compare in terms of Xcode work.
195: “The Swift historian”
John and Rambo celebrate the 5-year anniversary of the show by looking back at how their work and the technology they use have changed since the beginning of the show. Also, how might things change during the next 5 years, specifically when it comes to machine learning, AR, and the openness of Apple’s platforms?
194: “Definitely not called a puppy”
How game controllers communicate with a Mac, handling asynchronous data and actions in SwiftUI, and various ways to use view models within a code base.
193: “Build your own Mac”
Thoughts on the most recent Mac Pro rumors, building custom layouts for SwiftUI views in a backward-compatible manner, and the mechanics of making a UI interaction feel responsive and fluid.
192: “Sundell Silicon”
Building computers, running A/B tests as an indie developer, using UIKit as a layout tool for SwiftUI views, and deciding whether to use Core Data or a more simple on-disk data storage solution.
191: “Back to the future”
Building custom collection view layouts, introducing new features into a legacy code base, and managing patch releases while also working on a major new version of an app at the same time.
190: “Actual trips to the Dynamic Island“
John’s got the new AirPods Pro, Rambo’s got the iPhone 14 Pro, so the two share their initial impressions of using these new devices and how features like Dynamic Island and Adaptive Transparency work in day-to-day use.
189: “The UI equivalent of a singleton”
John and Rambo discuss three of the key announcements that Apple made during their “Far Out” event — the Apple Watch Ultra, the new AirPods Pro, and the iPhone 14 Pro.
188: “The least risky of the risky ones”
With Apple’s upcoming “Far Out” event just around the corner, John and Rambo share their predictions as to what new devices, services and features that might be announced. It’s Apple Keynote Poker time!
187: “An endless supply of SwiftUI thoughts”
John gains a new “job title”, Rambo starts working on an iOS version of AirBuddy, and the two discuss how come the Apple developer community tends to be so focused on UI frameworks.
186: “A relational database using Markdown”
John and Rambo share their initial impressions of some of the new APIs that were announced at WWDC22, and talk about managing releases, learning when and how to apply generics, and the launch of the Gigahertz podcast network.
185: “A big ‘finally’ moment”, the WWDC22 keynote review
John and Rambo discuss Apple’s WWDC22 keynote, and share their first impressions of the new features and APIs that were announced.
184: “State of anticipation”
It’s time for John and Rambo to play another round of Apple Keynote Poker! This time the two place their bets as to what Apple might introduce during the WWDC22 keynote and State of the Union session.
183: “Let’s just call it MVC”
Organizing workspaces and hobby projects, the pros and cons of view models and controllers, and rendering Core Animation layers within SwiftUI view hierarchies.
182: “Are you ready to enter a rabbit hole?”
A deep dive into how WidgetKit and SwiftUI’s serialization mechanism works under the hood, why John removed the ads from the Swift by Sundell website, and the discontinuation of the last iPod model.
181: “The banner effect”
Balancing refactoring with feature development, abstracting system services, and building delightful UIs.
180: “Production software is a lot of work”
Custom macOS virtualization on Apple Silicon, the pros and cons of SwiftUI’s List view, initial thoughts on WWDC 2022, and why Italy is such an amazing place.
179: “An iMac without the Mac”
New website, new logo, same show! Rambo shares his initial impressions of using Apple’s new Studio Display, along with some interesting spelunking results. Also, behind the scenes of the show’s new website, and a few web development tips.
178: “Let’s try something new”
John and Rambo celebrate the show’s 4th birthday with a big announcement, and then talk about security research, project priorities, and how to combine SwiftUI views with protocol-based observable objects.
177: “The stand is included!”
John and Rambo share their first impressions of the products announced at Apple’s “Peek Performance” event — including the new iPhone SE and iPad Air, M1 Ultra, Mac Studio and the Studio Display.
176: “Extra Keynote Poker”
On this extra episode of the show, John and Rambo share their bets, hopes and predictions for Apple’s upcoming “Peek Performance” event.
175: “A Bluetooth fanboy”
Unit testing SwiftUI-based views, view and data architecture, as well as a behind the scenes look at Rambo’s home automation setup.
174: “An operating system toolkit”
John and Rambo speculate what the SDK for Apple’s rumored AR/VR devices might look like, and what sort of user experiences that we might be able to build using it.
173: “The fabric of space-time”
SwiftUI for animations, prototyping, and game development. Plus, a second review of the M1 Max-based MacBook Pro, and an update on how well it performs for gaming.
172: “The ‘weak self’ dance”
How memory management works when using Swift’s new concurrency features, getting out of productivity traps, remote pair programming, and the process of installing Mac apps.
171: “Three levels of happiness”
Continued discussions around using SwiftUI for custom animations and layouts, more on phased rollouts and prioritizing bug fixes, content exclusivity and acquisitions, and various ways of sharing code across Apple’s platforms.
170: “Welcome to programming”
John and Rambo revisit the topic of SwiftUI and UIKit interoperability, and discuss which of the two UI frameworks that’s recommend for beginners to start with. Also, the launch of AirBuddy 2.5, and using phased rollouts when releasing new app versions.
169: “Choosing what bugs to ship”
Stacktrace is back! On this first episode of 2022, John and Rambo talk about their holidays, using Swift Playgrounds to build apps on the iPad, Mac gaming, and project goals.
168: “The 2021/2022 New Year’s Eve Special”
Join John and Rambo on this special New Year’s Eve episode of Stacktrace, on which they celebrate some of their favorite moments, products, media, and learnings from 2021.
167: “iPad is now Turing Complete”
John and Rambo share their first impressions of the newly released Swift Playgrounds 4, which enables developers to build full iOS apps right on the iPad. Also, the value of narrowly scoped open source libraries, and what it’s like using GitHub CoPilot in practice.
166: “A little bit of compiler magic”
The importance of sleep for both humans and async tasks, transferring apps and Apple developer accounts, and what things John and Rambo carry in their bags at all times.
165: “It’s not the technology, it’s the people”
John and Rambo discuss software quality trends, async functions and unit testing, Apple’s approach to private data with CloudKit, and dealing with technical debt.
164: “Your wattage may vary”
It’s time for the first ever Stacktrace Headphone Holiday Guide! Along with discussions about writing technical articles, view models and the MVVM design pattern, and using Swift actors to solve race conditions and data races.
163: “The Rambo Objective-C Manifest”
Rambo shares his set of principles for when and how to rewrite existing Objective-C code in Swift, John talks about his preferred workshop formats, and the two discuss the current state of Apple’s services.
162: “Hanging on the cliff for a whole week”
John and Rambo discuss asynchronous unit testing, using Windows as a development platform, SwiftUI previews on laptops, and conclude their deep dive into Swift’s concurrency system by talking about actors and structured concurrency.
161: “One big data transformation engine”
Rambo longs to get back to UI development, John releases a new open source project, and the two embark on part one of their deep dive into Swift’s new concurrency system. Also, organizing devices, and mechanical keyboards.
160: “M1 Macintoshes”
John shares his first impressions of the new 14-inch MacBook Pro and how he has been utilizing Swift’s new concurrency features to get the most out of the M1 Max. Also, Rambo’s work with Shortcuts, maintaining SwiftUI-based Mac apps, and much more.
159: “A really powerful new toy”
After a discussion about Swift generics and when to use them, Rambo shares his initial impressions of using the new iPad mini, and John explains why he’s going back to the Mac for his portable computing needs.
158: “Double unleashed”
The 14 and 16-inch Apple Silicon-based MacBook Pros have finally been revealed, and John and Rambo share their initial impressions of these new products and everything else that Apple announced during their “Unleashed” event.
157: “Very close to folding”
John and Rambo share their bets, hopes, and predictions for Apple’s upcoming “Unleashed” event. Will we finally see a new, Apple Silicon-powered MacBook Pro, and what other products might make an appearance at the event? Also, SwiftUI backward compatibility, and re-prioritizing projects in preparation for new OS releases.
156: “That time complexity problem”
John gets back into game development, Rambo builds a custom Bluetooth packet parser for AirBuddy, and the two embark on another technical deep dive — this time into the big topic of performance tuning.
155: “Embrace the bump”, the iOS 15 and iPhone 13 Pro review
What it’s been like for John to upgrade from the iPhone X to the iPhone 13 Pro, Rambo’s continued adventures into the depths of Bluetooth LE, and opinions on the final production versions of iOS 15 and iPadOS 15.
154: “The App Store paradise we all want”
After discussing various refactoring strategies and app extensions for iOS apps running on the Mac, John and Rambo dive into the latest App Store news, how Apple TV+ compares to its competitors, and how to switch networking environments within a beta app.
153: “California Streaming”
John and Rambo share their first impressions of the products announced at Apple’s “California Streaming” event — including the iPhone 13 lineup, the new iPad "Classic" and iPad mini, and the Apple Watch Series 7.
152: “Ultra Retina Smoothness”
After a few brief discussions about distributed systems and preparing code bases for Apple’s new operating systems, John and Rambo place their bets as to what Apple might announce during their upcoming “California Streaming” event. Will we see the iPhone 13, an Apple Watch Series 7, or perhaps something brand new?
151: “The iOS 15 season”
John and Rambo discuss the iOS 15 beta process, the latest round of App Store debates, Swift concurrency backward compatibility, and whether Apple should embrace a more continuous delivery process for new APIs and system features.
150: “A secret Catalyst agent”
On this 150th episode of the show, John and Rambo go on a series of accidental deep dives into universal links, how Catalyst and AppKit can be integrated, and more. Also, what does being a technical leader entail, and what’s the current state of Swift Evolution?
149: “Apple Watch development chooses you”
Prompted by recent rumors around a redesigned Apple Watch, John and Rambo discuss the state of the Watch as a platform, both as users, and from a development perspective. Also, managing an app’s colors, getting started with freelancing, and NSOperations.
148: “Do you have a plan for Apple?”
John’s new iPad development setup, Rambo’s widget layout challenges, and Apple’s (lack of a strong) home device strategy. Also, managing deadlines, maintaining SwiftUI views across multiple system versions, and continuous integration.
147: “The logic behind the pixels”
Rambo’s initial impressions of the Playdate developer tools, John’s process for keeping articles and sample code up to date, Google’s new Tensor chip, and designer/developer collaboration.
146: “Another straw on the back of the antitrust camel”
After an accidental deep dive into Git branching strategies and a discussion about app-wide data models, John and Rambo talk about the recent news that Netflix is getting into gaming, and what that could mean both content-wise and technically.
145: “Working code is better than good-looking code”
John and Rambo discuss some of the most recent Apple hardware rumors, how they’ve been John and Rambo discuss how they use unit testing to verify their code, and how automatic testing fits into their overall workflows. Also, more details about Rambo’s new app, and strategies for adding new features to existing code bases.
144: “An M1 with some sugar on top”
John and Rambo discuss some of the most recent Apple hardware rumors, how they’ve been changing their style of programming since the introduction of SwiftUI and Combine, and whether Swift package manifests could one day replace Xcode project files. Also, why does John always call Rambo by his last name?
143: “The biggest ‘it depends’ ever”
John and Rambo discuss the recent announcement of GitHub Copilot and the implications that such a tool could have on the world of software development. Also, deciding between SwiftUI and UIKit on a component level, and the power of relaxation.
142: “The Sideloading Cartel”
It’s the Stacktrace App Store special! What could happen if Apple were to enable sideloading on iOS, and what other changes could Apple make to improve the App Store and its relationship to third-party developers? Also, connecting Combine with async/await, using design tools, alternatives to using analytics SDKs, and much more.
141: “Going to space is more reliable than Bluetooth”
John’s new daily writing challenge, Rambo’s continued deep dives into Bluetooth and local networking, and initial impressions of Apple Music Spatial Audio. Also, what might the future of technologies like Objective-C and Combine look like, given this year’s WWDC announcements?
140: “I was applauding from my couch”
John and Rambo dive much deeper into some of the key new APIs and system features that were announced at WWDC21, including SharePlay, ShazamKit, Swift’s new concurrency system, and what’s new in Xcode 13. Also, debugging low-level crashes, and tips for getting started with app development.
139: “macOS Monorail”, the WWDC21 keynote review
John and Rambo discuss some of the major new announcements from Apple’s WWDC21 keynote, and how they might impact developers building apps for Apple’s platforms.
138: “WWDC21 Keynote Poker”
It’s time for another game of Stacktrace Keynote Poker! This time, John and Rambo place their bets on what Apple might announce at WWDC21, either during the main keynote, or as part of the more developer-focused State of the Union.
137: “State of the Union nap”
WWDC preparations, the challenge of building features that rely on wireless communication between devices, Apple’s latest accessibility announcements, and another semi-deep dive into Swift’s Result Builders feature.
136: “Cascading Device Sheets”
After narrowly avoiding an accidental web development deep dive, John and Rambo discuss the challenges of open source maintenance, AirBuddy’s upcoming battery notifications feature, the latest Mac-related rumors, and the new Apple Music hi-fi update.
135: “No overview available”
John and Rambo go on a deep dive into Plot’s new SwiftUI-like API for building HTML pages, and discuss 3D printing, API evolution and documentation, whether Apple ever considered letting third party developers ship apps outside of the iOS App Store, and how to pick what projects to pursue.
134: “Overthinking is the enemy of shipping”
After checking in on the progress of Rambo HQ 2.0 and a visit to John’s Static Site Generation Corner, John and Rambo briefly discuss the ongoing trial between Apple and Epic Games, and then dive into topics like project planning and how to pick what server-side framework to use for a new project.
133: “A flowchart in your head”
Organizing Combine-based code, the security of smart home devices, whether the Apple TV is gaining eARC support, and how to use compiler directives and launch arguments to customize an app at both compile time and runtime.
132: “The 'M' stands for 'Marketing'”
John and Rambo discuss all of the major announcements from Apple’s “Spring Loaded” event, including the new iMac, AirTags, the M1-powered iPad Pro, and the updated Apple TV. Also, the key factors that can help make a code base easier to navigate, and the benefits of going all-in on HomeKit.
131: “Apple product therapy”
It’s finally time for another round of Apple Event Keynote Poker, with John and Rambo placing their bets as to what Apple might announce during their “Spring Loaded” event on April 20th. Also, the power of HTTP, SwiftUI for AR, Swift’s Result Builders feature, and more.
130: “A comedian with code”
John and Rambo talk about Kara Swisher’s recent interview with Tim Cook, Apple’s upcoming App Tracking Transparency initiative and the new additions to Apple Arcade, and classic vs modern UIKit. Also, behind the scenes of this year’s April Fools’ jokes, and a somewhat unique #askStacktrace segment.
