Swift : telling callback to run on global queue - swift

Question

I'm running a background upload task but I found it's blocking the main thread. After looking I suspect this happens because 3rd party library (Firebase in this case) must be scheduling its async callback on the main thread.
Is there a way to explicitly make the callback run on the global thread?
Here's how I start the task from the main thread:
DispatchQueue.global(qos: .background).async {
PhotoUploadOperation().start()
}
Here's an oversimplified version of the upload task:
class PhotoUploadOperation {
func uploadCameraRoll() {
for element in photos {
self.uploadPhoto(element.image, uid) { url in
// Some work
if let url = url {
let photo = Photo(uid: uid, url: url, creationDate: element.date)
self.sendPhoto(photo: photo) { success in
// Some work
}
}
}
}
}
}

Answer 1

Could you try this solution?
Firebase or other 3party framework use "method swizling" to accomplish some network log or other things. But your scenario is a little bit different.
extension DispatchQueue {
static func background(delay: Double = 0.0, background: (()->Void)? = nil, completion: (() -> Void)? = nil) {
DispatchQueue.global(qos: .background).async {
background?()
if let completion = completion {
DispatchQueue.main.asyncAfter(deadline: .now() + delay, execute: {
completion()
})
}
}
}
}
Usage:
DispatchQueue.background(delay: 3.0, background: {
// do something in background
}, completion: {
// when background job finishes, wait 3 seconds and do something in main thread
})
DispatchQueue.background(background: {
// do something in background
}, completion:{
// when background job finished, do something in main thread
})
DispatchQueue.background(delay: 3.0, completion:{
// do something in main thread after 3 seconds
})
And you dont forget allow background processing from Signing and Capabilities