iOS: Progress bar in a different view controller

Question

I have 2 view controllers. In the parent view, i have a progress view. In the child VC, I am uploading an image with parameters using POST request to the server and then dismissing that VC and hence on returning to parent VC, I want progress View to update as the upload is happening. I tried protocol-delegate method, but looks like it only works once and can't return values dynamically. I tried implementing the following method in both view controllers but no success.

    func URLSession(session: NSURLSession, task: NSURLSessionTask, didSendBodyData bytesSent: Int64, totalBytesSent: Int64, totalBytesExpectedToSend: Int64) {

    self.progressView.hidden = false
    self.uploadProgress = Float(totalBytesSent) / Float(totalBytesExpectedToSend)
    print(self.uploadProgress)
    self.progressView.setProgress(self.uploadProgress, animated: true)

    if (uploadProgress == 1.0) {
        self.progressView.hidden = true
//            uploadProgress = 0.0
    }
}

@Shubhank maybe i am implementing that wrong, but shouldn't delegate method work once when we will dismiss VC. I tried calling it in above URLSession method too, but it is not working. — Karanveer Singh, Aug 31 '16 at 06:37

score 0 · Answer 1 · answered Aug 31 '16 at 07:39

0

Have a look on KVO (Key-Value observing) and observe your self.uploadProgress. Each time the self.uploadProgress is change a function will be called and then you can do whatever you want. Make sure to add the observer (function) on the VC you want to show the progress bar.

For example in ParentVC:

[childVC addObserver:self forKeyPath:@"uploadProgress" options: NSKeyValueObservingOptionNew context:NULL];

and then:

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {

    if ([keyPath isEqualToString:@"uploadProgress"]) {
        NSLog(@"Updated Value:%@",[change objectForKey:NSKeyValueChangeNewKey]);
        //Do something
    }
}

observeForValue will be called each time uploadProgress property change.

Don't forget to remove observer when you don't need it or when ChildVC will be destroyed.

-(void)dealloc {

    [self removeObserver:parentVC forKeyPath:@"uploadProgress"];
}

answered Aug 31 '16 at 07:39

BlackM

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I will try this in a while. Thanks, will let you know if this worked. – Karanveer Singh Aug 31 '16 at 09:53
Make sure that the reference from childVC to parentVC is weak in order to avoid retain cycle – BlackM Aug 31 '16 at 09:55
Thanks for the answer, but my own code worked. All I had to do was put the progress code inside dispatch_async. – Karanveer Singh Aug 31 '16 at 10:31
in main queue or background queue? If it's not in the main queue then probably your app will crash in the future since updating the UI from a background thread will cause a lot of issues. Anw take a look on KVO approach. It's ideal for that kind of issues – BlackM Aug 31 '16 at 11:10
It's in the main queue. – Karanveer Singh Aug 31 '16 at 11:16

iOS: Progress bar in a different view controller

1 Answers1