I’m attempting to learn Swift. I’m writing and testing a Class to encapsulate variables and methods to process a binary file of UInt16 values to produce and display a GCImage in an app for testing the Class which displays the grayscale image as the ultimate test.

At this point most everything worked and I was tidying up the code. Suddenly importing the file using Data produced a runtime error. The file could not be read.

Consulting Dr. Google was a waste of time. In the meantime I compared the file path input as a String vs the generated URL. The only difference was that spaces had been replaced by ‘%20’. I finally created some debug code to test that the data file actually existed (it’s in my file tree) and was readable – it is. I have inspected the entitlements file and the app is not Sandboxed and read permission is ‘Yes’. (In the process I somehow damaged the entitlements file, couldn’t recreate it so had to create a new app and copy all the code.) The error persists.

XCode and Swift are up-to-date, the app is only for macOS which is up-to-date.

The paths below are copied from debug data

    imagePath = (String)    "/Users/nate/2023 02 22 1330 SwiftDecomTestData/rawPlus/DN/IR3_2017-12-08_018_029_dn.raw"   
    fileURL Foundation.URL? "/Users/nate/2023%2002%2022%201330%20SwiftDecomTestData/rawPlus/DN/IR3_2017-12-08_018_029_dn.raw"

The code snippet where the error occurs.

    private func importAndScaleImageData() {
        // Start DEBUG verification
        let filePath = self.imagePath  // data file
        if checkIfFileExists(atPath: filePath) {
            print("file exists!")
            if !checkFileReadability(filePath: filePath) {
                print("Unable to read the file.")
                print("imagePath (filePath)")
                fatalError()
            }
        } else {
            print("file does not exist!")
            fatalError()
        }
        // No runtime errors above #########
        // END DEBUG verification

        do { // NOTE input file path as String was cast as URL
            let data8 = try Data(contentsOf: self.fileURL!) // ERROR
            self.backingImage = data8.uint16Array() // not reached
        } catch { // error caught here #######
            print("importAndScaleImageData: URL (self.fileURL!)  (error)")
            fatalError("Error found importing (self.fileURL!.absoluteString)")
        }

           // remainder of the method skipped 

        }