I’m trying to use the Vision framework in a Swift Playground to perform face detection on an image. The following code works perfectly when I run it in a regular Xcode project, but in an App Playground, I get the error:
Thread 12: EXC_BREAKPOINT (code=1, subcode=0x10321c2a8)
Here’s the code:
import SwiftUI
import Vision
struct ContentView: View {
var body: some View {
VStack {
Text("Face Detection")
.font(.largeTitle)
.padding()
Image("me")
.resizable()
.aspectRatio(contentMode: .fit)
.onAppear {
detectFace()
}
}
}
func detectFace() {
guard let cgImage = UIImage(named: "me")?.cgImage else { return }
let request = VNDetectFaceRectanglesRequest { request, error in
if let results = request.results as? [VNFaceObservation] {
print("Detected (results.count) face(s).")
for face in results {
print("Bounding Box: (face.boundingBox)")
}
} else {
print("No faces detected.")
}
}
let handler = VNImageRequestHandler(cgImage: cgImage, options: [:])
do {
try handler.perform([request]) // This line causes the error.
} catch {
print("Failed to perform Vision request: (error)")
}
}
}
The error occurs on this line:
try handler.perform([request])
Details:
- This code runs fine in a normal Xcode project (
.xcodeproj). - I’m using an App Playground instead (
.swiftpm). - The image is being included in the
.xcassetsfolder.
Is there any way I can mitigate this issue? Please do not recommend switching to .xcodeproj, as I am making a submission for Apple’s Swift Student Challenge, and they require that I use .swiftpm.
2
Using the methodology behind this solution, I was able to fix the issue.
I have now incorporated modern Swift concurrency utilizing async/await and withCheckedThrowingContinuation.
import SwiftUI
@preconcurrency import Vision
struct ContentView: View {
var body: some View {
VStack {
Text("Face Detection")
.font(.largeTitle)
.padding()
Image("me")
.resizable()
.aspectRatio(contentMode: .fit)
.task {
await detectFace()
}
}
}
func detectFace() async {
guard let cgImage = UIImage(named: "me")?.cgImage else { return }
let request = VNDetectFaceRectanglesRequest()
let handler = VNImageRequestHandler(cgImage: cgImage, options: [:])
do {
try await performVisionRequest(request: request, handler: handler)
if let results = request.results {
print("Detected (results.count) face(s).")
for face in results {
print("Bounding Box: (face.boundingBox)")
}
} else {
print("No faces detected.")
}
} catch {
print("Failed to perform Vision request: (error)")
}
}
private func performVisionRequest(request: VNRequest, handler: VNImageRequestHandler) async throws {
try await withCheckedThrowingContinuation { continuation in
do {
try handler.perform([request])
continuation.resume()
} catch {
continuation.resume(throwing: error)
}
}
}
}
3