Cannot create Data for Multi Part Form request - swift

Question

I am trying to send a multipart/form-data request via URLSession I have written a helper function to create the form body as Data for me, however my request keeps failing with a 500 response code.
I was trying to print out the string representation of my request to ensure the body is correct, however simply trying to decode it now is throwing an error as The data couldn’t be read because it isn’t in the correct format.
This leads me to believe something is wrong with how my request is being encoded.
This is essentially my setup -
struct Media {
let key: String
let filename: String
let data: Data
let mimeType: String
init?(withImage image: UIImage, forKey key: String) {
self.key = key
self.mimeType = "image/jpeg"
self.filename = "avatar.jpg"
guard let data = image.jpegData(compressionQuality: 0.7) else { return nil }
self.data = data
}
}
typealias Parameters = [String: String]
func createFormData(usingParams params: Parameters?, media: [Media]?, boundary: String) -> Data {
let lineBreak = "\r\n"
var body = Data()
if let parameters = params {
for (key, value) in parameters {
body.append(string:"--\(boundary + lineBreak)")
body.append(string:"Content-Disposition: form-data; name=\"\(key)\"\(lineBreak + lineBreak)")
body.append(string:"\(value + lineBreak)")
}
}
if let media = media {
for photo in media {
body.append(string:"--\(boundary + lineBreak)")
body.append(string:"Content-Disposition: form-data; name=\"\(photo.key)\"; filename=\"\(photo.filename)\"\(lineBreak)")
body.append(string:"Content-Type: \(photo.mimeType + lineBreak + lineBreak)")
body.append(photo.data)
body.append(string: lineBreak)
}
}
body.append(string: "--\(boundary)--\(lineBreak)")
return body
}
extension Data {
mutating func append(string: String) {
if let data = string.data(using: .utf8) {
append(data)
}
}
}
Which I invoke something like this -
let boundary = UUID().uuidString
guard let profilePic = Media(withImage:image, forKey: "file") else { return }
let data = createFormData(usingParams: nil, media: [profilePic], boundary: boundary)
I have tried to print my data using the following -
do {
print(data)
let json = try JSONSerialization.jsonObject(with: data, options: []) as? [String : Any]
print(json)
} catch let error {
print(error.localizedDescription)
}
This throws the error mentioned earlier.
I have also tried
let string = String(data: data, encoding: .utf8)
print(string)
This however just returns nil.
I noticed if I remove body.append(photo.data) the data can print out now as JSON, however I am not sure why this matters