SwiftUI Challenge #2 - https://twitter.com/objcio/status/1227608799478829058?s=20

SignalStrengthIndicator.swift

import SwiftUI

struct SignalStrengthIndicator: View {
    /// Spacing between individual bars.
    @State var barSpacing: CGFloat = 2
    /// Minimal height of a bar (`0.1` means 10% of the actual height).
    @State var minBarHeight: CGFloat = 0.1
    /// Individual bar corner radius.
    @State var barCornerRadius: CGFloat = 8.0

    /// Number of highlighted bars.
    @State var bars: Int = 2

    /// Total number of bars.
    @State var totalBars: Int = 5

    var body: some View {
        HStack(spacing: barSpacing) {
            ForEach(0 ..< totalBars) { idx in
                RoundedRectangle(cornerRadius: self.barCornerRadius, style: .continuous)
                    .scale(x: 1.0, y: self.scaleY(for: idx), anchor: .bottom)
                    .fill(idx < self.bars ? Color.primary : Color.secondary)
            }
        }
    }

    private func scaleY(for index: Int) -> CGFloat {
        guard totalBars > 1 else { return 1.0 }
        return self.minBarHeight + (1.0 - minBarHeight) / .init(totalBars - 1) * .init(index)
    }
}

struct SignalStrengthView: View {
    var body: some View {
        HStack(alignment: .center) {
            SignalStrengthIndicator(bars: 2, totalBars: 5)
                .aspectRatio(2.3, contentMode: .fit)

            Text("-75 db")
                // TODO: Would be nicer to have a dynamic padding based on the font size
                .padding([.bottom, .top], 6.0)
                .layoutPriority(1)
        }
    }
}

#if DEBUG

struct SignalStrengthIndicator_Previews: PreviewProvider {
    static var previews: some View {
        VStack(spacing: 30) {
            HStack(spacing: 10) {
                SignalStrengthIndicator(bars: 0, totalBars: 5)
                    .frame(width: 70, height: 30)

                SignalStrengthIndicator(bars: 2, totalBars: 5)
                    .frame(width: 70, height: 30)

                SignalStrengthIndicator(bars: 5, totalBars: 5)
                    .frame(width: 70, height: 30)
            }

            HStack(spacing: 10) {
                SignalStrengthIndicator(bars: 0, totalBars: 5)
                    .frame(width: 70, height: 60)

                SignalStrengthIndicator(bars: 2, totalBars: 5)
                    .frame(width: 70, height: 60)

                SignalStrengthIndicator(bars: 5, totalBars: 5)
                    .frame(width: 70, height: 60)
            }

            HStack(spacing: 10) {
                SignalStrengthIndicator(bars: 0, totalBars: 5)
                    .frame(width: 100, height: 30)

                SignalStrengthIndicator(bars: 2, totalBars: 5)
                    .frame(width: 100, height: 30)

                SignalStrengthIndicator(bars: 5, totalBars: 5)
                    .frame(width: 100, height: 30)
            }

            SignalStrengthView()
                .font(.caption)

            SignalStrengthView()

            SignalStrengthView()
                .font(.largeTitle)

            Spacer()
                .layoutPriority(1)
        }
        .padding()
    }
}

#endif