Weird error when trying to make a http multipart-form data request in swiftui

Question

Here is the code for uploading a file using a POST request and form-data body type.

let contentType = "multipart/form-data; boundary=\(boundary)"
urlRequest.setValue(contentType, forHTTPHeaderField: "Content-Type")

let fileName:String = String(request.fileURLForFormData!.path().split(separator: "/").last ?? "")
let fileData = try Data(contentsOf: request.fileURLForFormData!)
var uploadData = Data()

// Append file data
uploadData.append("--\(boundary)\r\n".data(using: .utf8)!)
uploadData.append("Content-Disposition: form-data; name=\"image\"; filename=\"\(fileName)\"\r\n".data(using: .utf8)!)
uploadData.append("Content-Type: \(fileName.mimeType())\r\n\r\n".data(using: .utf8)!)
uploadData.append(fileData)
uploadData.append("\r\n".data(using: .utf8)!)

// Close the form data
uploadData.append("--\(boundary)--\r\n".data(using: .utf8)!)

// Set the request body
urlRequest.httpBody = uploadData
let (data, response) = try await URLSession.shared.upload(for: urlRequest, from: Data(contentsOf: request.fileURLForFormData!))

return .success((data, response))

Here is the error i am getting using data, dataTask, upload and uploadTask.

The request of a upload task should not contain a body or a body stream, use upload(for:fromFile:), upload(for:from:), or supply the body stream through the urlSession(_:needNewBodyStreamForTask:) delegate method.

Answer 1

When you create an upload request, the parameter you pass as data: gets sent as the request body. To the body data you'd actually be sending right now is the raw file data, not the form-encoded data.

And the API also complains because you shouldn't be setting the body on the request at all.

To fix this:

• Pass the uploadData object as the from: parameter when creating the request instead of passing the contents of the file on disk.
• Delete the line that sets urlRequest.httpBody.