Equal widths of subviews with SwiftUI

I'm still confused about when and how relativeWidth is supposed to be used, but I was able to achieve want I wanted without using it. (EDIT 18 July 2019: According to the iOS 13 Beta 4 release notes, relativeWidth is now deprecated)

In the last update to my question I had some extra spacing between the two sides, and realized that was the default spacing coming in on the HStack and I was able to remove that by setting its spacing to 0. Here's the final code and result:

var body: some View {
    VStack {
        HStack(spacing: 0) {

            VStack {
                Text("Short").font(.body)
            }
                .frame(minWidth: 0, maxWidth: .infinity)
                .background(Color.green)

            VStack {
                Text("Longer!!!").font(.body)
            }
                .frame(minWidth: 0, maxWidth: .infinity)
                .background(Color.blue)

        }
            .frame(minWidth: 0, maxWidth: .infinity)
            .background(Color.yellow)
        Button (action: doSomething) {
            Text("|")
        }
    }
}

And here is the result:

You have set background of HStack to yellow color and HStack has some default inter child views spacing. By adding spacing: 0 in HStack will solve the problem see the updated code below.

var body: some View {
    VStack {
        HStack(spacing: 0) { // Set spacing here
            VStack {
                Text("Short").font(.body)
            }
                .frame(minWidth: 0, maxWidth: .infinity)
                .background(Color.green)

            VStack {
                Text("Longer!!!").font(.body)
            }
                .frame(minWidth: 0, maxWidth: .infinity)
                .background(Color.blue)

        }
            .frame(minWidth: 0, maxWidth: .infinity)
            .background(Color.yellow)
        Button (action: doSomething) {
            Text("|")
        }
    }
}