Slightly Advanced Core Data

Posted on Sat 31 July 2021 in swift

I got some work done on 100 Days of SwiftUI yesterday (the 30th) but I didn't do a generative art sketch or write this blog post until today (the 31st). Continued stomach issues, combined with visiting family, managed to derail me.

Lots of new stuff in Core Data & SwiftUI for me yesterday, including a nice pattern for dynamically filtering a @FetchRequest with a custom SwiftUI view.

I tried doing today's Generative Art sketch in a slightly different way. I've been frustrated that I haven't figured out good ways to abstract the drawing commands I want to execute inside the Canvas object. In particular, I haven't figured out how to just pass it a Shape file and say "stroke this Shape in this CGRect using these line characteristics." It seems possible with context.resolveSymbol() but I haven't gotten that to work. So today I tried making an extension on Path to create a custom initializer, a la Path(ellipseIn:) that would just draw my custom Path inside any rect I wanted. It mostly worked, but abstracting the Path away like that also makes it harder to change lineweight or stroke color on just a part of that Path, since that's done further out in the Canvas context. So I guess tradeoffs.

extension Path {
    init(radiatingLinesIn rect: CGRect, lineCountPerSide: Int = 10) {
        assert(lineCountPerSide >= 1, "line count per side must be at least 1")

        let origin = CGPoint(x: rect.midX, y: rect.midY)

        for side in 0..<4 {
            var x2: CGFloat = .zero
            var y2: CGFloat = .zero

            for i in 0..<lineCountPerSide {
                if side == 0 {
                    // top side - left to right
                    x2 = rect.minX + (rect.size.width / CGFloat(lineCountPerSide)) * CGFloat(i)
                    y2 = rect.minY
                } else if side == 1 {
                    // left side, bottom to top
                    x2 = rect.minX
                    y2 = rect.maxY - (rect.size.height / CGFloat(lineCountPerSide)) * CGFloat(i)
                } else if side == 2 {
                    // right side, top to bottom
                    x2 = rect.maxX
                    y2 = rect.minY + (rect.size.height / CGFloat(lineCountPerSide)) * CGFloat(i)
                } else if side == 3 {
                    // bottom side, right to left
                    x2 = rect.maxX - (rect.size.width / CGFloat(lineCountPerSide)) * CGFloat(i)
                    y2 = rect.maxY
                let end = CGPoint(x: x2, y: y2)
                move(to: origin)
                addLine(to: end)

Line modules