I have implemented the following NSOperation, to draw N custom views
- (void)main {
for (int i=0; i<N; i++) {
<< Alloc and configure customView #i >>
//(customView is a UIView with some drawing code in drawrect)
[delegate.view addSubview:customView];
}
NSLog(@"Operation completed");
}
in the drawRect method of the customView I have
- (void)drawRect {
<<Drawing code>>
NSLog(@"Drawed");
delegate.drawedViews++;
if (delegate.drawedViews==VIEWS_NUMBER) {
[delegate allViewsDrawn];
}
}
So the delegate get the notification when all the views are drawn.
The problem is that after the "Operation completed" log it takes about 5 seconds before I can see the first "Drawed" log.
Why is this happening? And generally speaking, how should I behave in order to find out which line of code is taking so much time being executed?
------ EDIT ------
Sometimes (like 1 out of 10 times) I was getting crashes doing this because I shouldn't call addsubview from the NSOperation since it is not thread-safe. So I changed it to:
[delegate.view performSelectorOnMainThread:@selector(addSubview:) withObject:customView waitUntilDone:NO];
Now I don't have crashes anymore, but the process takes a very long time to be executed! Like 5 times more than before.
Why is it so slow?
To make things work properly we need to forget about NSOperation and use this "trick"
dispatch_queue_t main_queue = dispatch_get_main_queue();
dispatch_async(main_queue, ^{
[self createCustomViews];
dispatch_async(main_queue, ^{
[self addAnotherCustomViewToView];
});
});