Printing Log in iOS

Question

I need to show log outputs in a textview then and there in my app. I tried using performSelector inside my sequence but it did not work as I thought it would. Can someone show me how to do it?

For example, when I click a button, I do lot of operations underneath, and I want to display the logs in the textview then and there, not after the entire operation is done.

Plus can't I call performSelector more than once inside the same sequence?

Below is the sequence inside the button click:

- (IBAction)Write:(id)sender {

 //do some action here
 DisplayString = @"Seq1 pass"
 [self performSelector:@selector(updateviewText) withObject:nil afterDelay:0];
 //do some more action
 DisplayString = @"Seq2 pass"
 [self performSelector:@selector(updateviewText) withObject:nil afterDelay:0];
 ....
}

This the updateviewText part:

-(void)updateviewText {
        dispatch_queue_t queueNew = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0);
        dispatch_async(queueNew,^ {

        dispatch_async(dispatch_get_main_queue(),^{
            [self.txtViewUseCaseLOG setText:[NSString stringWithFormat:@"%@\n%@", 
                                       self.txtViewUseCaseLOG.text,DisplayString ]];             
        });           
    });
}

The DisplayString is a global variable here.

This code doesn't setText to the textview then and there... But as I asked earlier I need those messages then and there...

Answer 1

You can't update the UI asynchronously. If you're doing task asynchronously and want to update the UI you have to use dispatch_sync.

And why would you when you're doing something asynchronously open another asynchronous task?

Next thing is that if you're only using DisplayString in these two methods you might better add a NSString parameter to updateViewText so you don't need the global variable.