NEW: Learn SwiftUI with my free YouTube video series! >>

< How to draw a checkerboard   How to create basic animations >

How to use UIBezierPath and CGPath in SwiftUI

If you have existing paths made using UIBezierPath or CGPath it’s trivial to convert them for use in SwiftUI because the Path struct has an initializer directly from CGPath.

Note: UIBezierPath is not available in macOS, so if you’re trying to keep your SwiftUI code cross platform you should migrate to CGPath instead.

As an example, here’s a UIBezierPath extension I made to store the logo for an app I built, called Unwrap:

extension UIBezierPath {
    /// The Unwrap logo as a Bezier path.
    static var logo: UIBezierPath {
        let path = UIBezierPath()
        path.move(to: CGPoint(x: 0.534, y: 0.5816))
        path.addCurve(to: CGPoint(x: 0.1877, y: 0.088), controlPoint1: CGPoint(x: 0.534, y: 0.5816), controlPoint2: CGPoint(x: 0.2529, y: 0.4205))
        path.addCurve(to: CGPoint(x: 0.9728, y: 0.8259), controlPoint1: CGPoint(x: 0.4922, y: 0.4949), controlPoint2: CGPoint(x: 1.0968, y: 0.4148))
        path.addCurve(to: CGPoint(x: 0.0397, y: 0.5431), controlPoint1: CGPoint(x: 0.7118, y: 0.5248), controlPoint2: CGPoint(x: 0.3329, y: 0.7442))
        path.addCurve(to: CGPoint(x: 0.6211, y: 0.0279), controlPoint1: CGPoint(x: 0.508, y: 1.1956), controlPoint2: CGPoint(x: 1.3042, y: 0.5345))
        path.addCurve(to: CGPoint(x: 0.6904, y: 0.3615), controlPoint1: CGPoint(x: 0.7282, y: 0.2481), controlPoint2: CGPoint(x: 0.6904, y: 0.3615))
        return path

That uses control points that are normalized to the range of 0 through 1, so that I can render it inside any kind of container and just scale it up to fit the available space.

In SwiftUI that would mean creating a transform that scales the Bezier path up by the minimum of either the width or the height, then applying that to a path, like this:

struct ScaledBezier: Shape {
    let bezierPath: UIBezierPath

    func path(in rect: CGRect) -> Path {
        let path = Path(bezierPath.cgPath)

        // Figure out how much bigger we need to make our path in order for it to fill the available space without clipping.
        let multiplier = min(rect.width, rect.height)

        // Create an affine transform that uses the multiplier for both dimensions equally.
        let transform = CGAffineTransform(scaleX: multiplier, y: multiplier)

        // Apply that scale and send back the result.
        return path.applying(transform)

With all that in place, we can now render any kind of Bezier path we want:

struct ContentView: View {
    var body: some View {
        ScaledBezier(bezierPath: .logo)
            .stroke(lineWidth: 2)
            .frame(width: 200, height: 200)

If you’re starting with a CGPath rather than a UIBezierPath, things are even easier. This line:

let path = Path(bezierPath.cgPath)

Becomes this:

let path = Path(yourCGPath)

SPONSOR Meet the new Instabug – more than just bug reporting! We help you build better apps and minimize your debugging time. With each bug report, we automatically capture details like network requests, repro steps, and session details. Get real-time crash reports with stack trace details and session data to help you catch and fix issues easily. And with our customizable in-app surveys, you’ll gather insightful user feedback and much more. Instabug is the fastest and easiest way to release with confidence. Start your free trial now! Start your free trial now!

< How to draw a checkerboard   How to create basic animations >
Buy Testing Swift Buy Practical iOS 12 Buy Pro Swift Buy Swift Design Patterns Buy Swift Coding Challenges Buy Server-Side Swift (Vapor Edition) Buy Server-Side Swift (Kitura Edition) Buy Hacking with macOS Buy Advanced iOS Volume One Buy Advanced iOS Volume Two Buy Hacking with watchOS Buy Hacking with tvOS Buy Hacking with Swift Buy Dive Into SpriteKit Buy Swift in Sixty Seconds Buy Objective-C for Swift Developers Buy Beyond Code

Was this page useful? Let me know!

Click here to visit the Hacking with Swift store >>