Jan Stehlík
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jstehlik.cz
Jan Stehlík
@jstehlik.cz
2025 - the year when all developers the world over, all of them at once, were absolutely right.
October 30, 2025 at 1:42 PM
I still don't get how y'all get LLMs to output useful code.

I find them useful for isolated snippets and documentation, but they completely break down on anything more complex.

There is a threshold at which the output stops being useful and instead becomes a burden.
a dog wearing glasses sits at a computer keyboard
ALT: a dog wearing glasses sits at a computer keyboard
media.tenor.com
October 1, 2025 at 9:18 PM
One under-reported and easily misunderstood concept of @swift.org concurrency is blocking vs suspension. I created a simple gist for experimentation, which helped me solidify these foundational concepts. gist.github.com/blu-Fox/c184...
A simple view to test 3 async-related concepts: 1. blocking a thread 2: suspending a task 3: overwhelming a thread
A simple view to test 3 async-related concepts: 1. blocking a thread 2: suspending a task 3: overwhelming a thread - TaskSuspensionView.swift
gist.github.com
September 21, 2025 at 8:36 PM
#SwiftUI iOS26 crash: if you're getting crashes for missing Environment object, check your result builders! Starting in iOS26, @AxisContentBuilder fails to propagate an Observable object passed through SwiftUI Environment. Feedback submitted at FB20279212. See gist: gist.github.com/blu-Fox/eaa4...
FB20279212: @AxisContentBuilder fails to propagate an Observable object passed through SwiftUI Environment
FB20279212: @AxisContentBuilder fails to propagate an Observable object passed through SwiftUI Environment - TestView.swift
gist.github.com
September 17, 2025 at 12:33 PM
2025 summer vibes be like:
August 25, 2025 at 8:53 AM
#iosdev can we agree to delete all #concurrency blog posts written before #swiftlang 6.2+? This soup of keywords is not getting any easier if we (and our LLMs) swim in a sea of outdated advice.
August 7, 2025 at 6:42 AM
July 31, 2025 at 9:42 AM
@alexozun.com I finally watched your Typestate pattern talk. Really well done!
In the back of my mind I have a question about performance. If the model, e.g. Car, has lots of value type properties. Surely it's not good to copy all of them all of the time?
July 22, 2025 at 9:42 AM
Reposted by Jan Stehlík
June 19, 2025 at 8:29 PM
Word of the day: **monomorphization**.

It jumped at me during my ongoing deep dive into dispatch mechanisms of @swift.org.

So anyway, here is a monomorph, the compiled younger brother of the xenomorph.

Have a fun #WWDC everybody! 🥳
June 9, 2025 at 1:59 PM
@massicotte.org what's your take on Swift 6.2 changes in concurrency? My understanding is that `nonisolated(nonsending)` will break the rule that isolation is controlled by definitions.
June 3, 2025 at 9:55 AM
⚠️ I challenge you to find an easier way to crash #SwiftUI
April 2, 2025 at 8:16 AM
Pure #SwiftUI 🪄
April 1, 2025 at 8:01 AM
@massicotte.org thanks again for a stellar meetup on the topic of #Swift concurrency on Saturday. I took a deep dive into your excellent blog. I’m starting to think the `nonisolated` keyword is misleading.
a black and white photo of a man putting a sign on a wall that says isolation .
ALT: a black and white photo of a man putting a sign on a wall that says isolation .
media.tenor.com
March 5, 2025 at 9:48 AM
Shoutout to @bring-shrubbery.bsky.social, who created the absolutely amazing SVG to #SwiftUI Shape converter. 🔥 Made my day!
February 26, 2025 at 7:18 AM
Reposted by Jan Stehlík
When Russians spread propaganda about Ukrainian elections, realize that tampering with Ukrainian elections is the only realistic way for Russia to achieve their long term ambitions.
He will use propaganda to divide the people of Ukraine against each other. The society will fragment, and he will take advantage of the right wing elements of society to manipulate them into electing a government under Putin's control.
February 15, 2025 at 1:48 PM
We don’t even say we’re sorry, because we’ve been put under a gag order. I can’t even talk to my partners. I can’t even say, “Hey I’m really sorry to have totally fucked you over and your life.” www.politico.com/news/magazin...
‘Americans Can and Will Die from This’: USAID Worker Details Dangers, Chaos
The sudden scapegoating of the once-bipartisan agency has left front-line workers in foreign countries stunned and abandoned, without even a contact in Washington.
www.politico.com
February 11, 2025 at 7:34 AM
Reposted by Jan Stehlík
Heroes
January 30, 2025 at 8:37 PM
Reposted by Jan Stehlík
Work on Monday :(
January 2, 2025 at 10:25 PM
🎄🍪Christmas gingerbread: ✅
December 9, 2024 at 6:38 PM
@asianometry.bsky.social thought you might be interested in this 1973 video about Czechoslovak Tesla, where they showcase lithography and many other processes. www.youtube.com/watch?v=PW0R...
Tesla Rožnov - Od elektronek k integrovaným obvodům (1973)
YouTube video by Odkaznik CZ
www.youtube.com
December 2, 2024 at 7:03 AM
WIDGETS: GAME CHANGER OR GIMMICK? Developers, have you seen an uptick in users as a result of interactive widgets? I like them and my apps have them, but as a user, I almost never actually use them 🧐
November 26, 2024 at 8:17 PM
Reposted by Jan Stehlík
This moment in Bluesky is a great example of how joy itself can be defiance and resistance.

We are just hanging out, shitposting, being silly, happy, and normal. It is being treated as if it is transgressive, opting out of the endless negativity. Because in a way, it is.

Joy is my favorite weapon.
November 24, 2024 at 10:34 PM
Hi everyone, let’s make Bluesky a better place, *our* place 😊
I look forward to learning from and helping other developers for 🍏 platforms! #swiftui
November 23, 2024 at 9:26 AM