dynamic swift talk notes.md

Swift Evolution proposals for the three features I covered:

• Dynamic Member Lookup
• Dynamic Callable
• Key Path Member Lookup

Here's a good (and mildly critical) overview of dynamic member lookup.

Python interop:

• Library to use Python with normal Swift
• Plotting library I used in tonight’s demo
• Using Python with Swift for TensorFlow
• Rationale for not using static type wrappers for Python libs

Here's the excellent WWDC talk that talks about keypath member lookup, mingled in among many other things. Well worth watching the whole thing!

Python Interop Example

Setup

pip3 install plotly

mkdir python-interop
cd python-interop

swift package init --type executable

Package.swift

import PackageDescription

let package = Package(
    name: "python-interop",
    dependencies: [
        .package(url: "https://github.com/pvieito/PythonKit.git", .branch("master")),
    ],
    targets: [
        .target(
            name: "python-interop",
            dependencies: ["PythonKit"])
    ]
)

main.swift

import PythonKit
import Foundation

func swirlData(size: Int) -> [[Double]] {
  return (0..<size).map { x in
    (0..<size).map { y in
      let x = Double(x) / Double(size) * 2 - 1
      let y = Double(y) / Double(size) * 2 - 1
      let r = hypot(y, x) * 2
      let Θ = atan2(y, x)
      return cos(r * 5 + Θ * 3) * cos(x) * cos(y)
    }
  }
}

let data = swirlData(size: 120)

let plotly = Python.import("plotly.graph_objects")

let countour = plotly.Contour(z: data, line_smoothing: 1)
let fig = plotly.Figure(data: countour)
fig.shoow()

let surface = plotly.Surface(z: data)
let fig2 = plotly.Figure(data: [surface])
fig2.show()

Key Path Member Lookup Example

import Foundation

struct Name {
  var first, last: String
}

@dynamicMemberLookup
struct WriteLogger<T> {
  var value: T

  subscript<U>(dynamicMember keyPath: WritableKeyPath<T, U>) -> U {
    get {
      self.value[keyPath: keyPath]
    }
    set {
      print("New value: \(newValue)")
      self.value[keyPath: keyPath] = newValue
    }
  }

  subscript<U>(dynamicMember member: String) -> String {
    return "Woooot \(member)"
  }
}

var name = WriteLogger(value: Name(first: "Sally", last: "Jones"))
print(name.frist)
name.first = "Ultrasally"
name.last = "the Ultimate"