Cs193p on blog.iankulin.com

@ScaledMetric

Fri, 29 Jul 2022 00:00:00 +0000

I solved the problem (well, I googled a stackoverflow result to the problem) in the previous post about the different heights of the SF Symbols. The answer was to put them in a frame and lock the height. A problem that then arises from that is that when the user changes the text size, they’ll be out of wack. Apple’s solution to that, introduced in iOS 14 is the @ScaledMetric property wrapper that does some magic I don’t fully understand yet.

Memorise Assignment 1

Thu, 28 Jul 2022 00:00:00 +0000

A small milestone achieved - I’ve completed the first assignment from the CS193p lecture series - some minor changes to the app being built in the lectures. There was a couple of things I was unhappy with:

The text under the SF Symbols you can see in the preview above not being vertically aligned.
Having duplicated code in my emoji arrays:

 let animalEmojis = ["🐠", "🐢", "🦋", "🐥", "🐣", "🐰", "🐝", "🦄", "🐵", "🐛"]
 let weatherEmojis = ["🌪", "🌝", "🌈", "🔥", "🌧", "🌙", "🌬", "☃️", "☔️", "🌫"]
 let transportEmojis = ["🚗", "🚕", "🚲", "🚚", "🛵", "🚜", "🛴", "🛺", "🚃", "🚡"]

 // I'm not happy with this duplication //TODO
 @State var emojis = ["🐠", "🐢", "🦋", "🐥", "🐣", "🐰", "🐝", "🦄", "🐵", "🐛"]

This second problem is because I couldn’t just

@State var emojis = animalEmojis

When I tried it, I encountered the error:

Cannot use instance member 'animalEmojis' within property initializer; property initializers run before 'self' is available

This is vexing - the constants are defined on the lines above, so surely if this property exists, the ones before it do. Apparently that can’t be depended on - probably for some good reason that will be unveiled at some stage. It’s not because emojis is wrapped in the @State which probably does cause the variable to be created off somewhere else - I tried with just an ordinary var and had the same issue.

Then I read further down into the assignment, there’s a “hints section” which I should clearly be reading before I being. C’s get degrees.

Message received. Don’t worry about the doubled up string array, and go back and watch the lecture again. There was something about locking an aspect ratio for an SF Symbol at some stage.

CS193p

Thu, 07 Jul 2022 00:00:00 +0000

I’ve loved the first couple of these “Getting Started with SwiftUI” lectures from Paul Hegarty at Stanford. He’s put a lot of thought into the sequence, and seems to address the questions that float up in my mind (with super clear explanations) just as I’m thinking of them. They also generously make the reading and homework assignments available at cs193p.sites.stanford.edu so it’s possible to treat it as a course which I have made a bit of a start on, before being distracted by building my own simple app.

I’m currently on lecture 3 which was enough to get an MVP (minimum viable product) of EasterDay working in Playgrounds. I had intended it to be a demo of a simple MMVV setup, but by the time I’d refactored my model down to a struct containing a single int and a function it seemed silly.

I want to get back to following these lectures through, so I might combine that with figuring out GitHub.