Grid lines

February 4, 2023

---

A GeometryReader can be used to equally space lines in a view even when that view changes size. This is accomplished by using the width and height of the container view to determine the spacing of the lines.

import SwiftUI

struct ContentView: View {

    let xSteps = 5  // purple lines for x-axis grid
    let ySteps = 4  // black lines for y-axis grid

    var body: some View {
        ZStack(alignment: .top) {
            GeometryReader { geometry in
                Rectangle()
                    .fill(Color.gray)

                // x-axis grid shown as purple lines
                ForEach(0..<self.xSteps+1) {
                    Rectangle()
                        .fill(Color.purple)
                        .frame(width: 3)
                        .offset(x: geometry.size.width / CGFloat(self.xSteps) * CGFloat($0), y: 0.0)
                }

                // y-axis grid shown as black lines
                ForEach(0..<self.ySteps+1) {
                    Rectangle()
                        .fill(Color.black)
                        .frame(height: 3)
                        .offset(x: 0.0, y: geometry.size.height / CGFloat(self.ySteps) * CGFloat($0))
                }
            }
        }
        .frame(minWidth: 400, minHeight: 300)
        .padding()
        .background(Color.secondary)
    }
}