Xcode and tag searching - ios

Question

A simple inquiry.
When using Objective-C / Swift and one decides to implement tags for objects within the storyboard, how does the system search for the tags?
Does it approach this as a linear search? Therefore, implying that tags with a lower number value will be faster to search for? Or does it approach this entirely differently?
For example:
UIImageView *imageView = (UIImageView *)[self viewWithTag:1];
imageView.image = [UIImage imageNamed: #"Elderberries"];
vs
UIImageView *imageView = (UIImageView *)[self viewWithTag:100000000];
imageView.image = [UIImage imageNamed: #"Motherless_Goat"];
Thanks

Answer 1

I did some experiment, below is the code
//adding 30000 tag at first position
UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 20, 20)];
label.text = [NSString stringWithFormat:#"%d", 30000];
label.tag = 30000;
[self.view addSubview:label];
for (int i = 0; i < 30000; i++) {
UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 20, 20)];
label.text = [NSString stringWithFormat:#"%d", i];
label.tag = i;
[self.view addSubview:label];
}
NSTimeInterval currentTime, fetchTime;
currentTime = CFAbsoluteTimeGetCurrent();
UILabel *label1 = (UILabel *)[self.view viewWithTag:5];
fetchTime = CFAbsoluteTimeGetCurrent();
NSLog(#"Label:%# = %f",label1.text, fetchTime - currentTime);
currentTime = CFAbsoluteTimeGetCurrent();
UILabel *label2 = (UILabel *)[self.view viewWithTag:100];
fetchTime = CFAbsoluteTimeGetCurrent();
NSLog(#"Label:%# = %f",label2.text, fetchTime - currentTime);
currentTime = CFAbsoluteTimeGetCurrent();
UILabel *label3 = (UILabel *)[self.view viewWithTag:1000];
fetchTime = CFAbsoluteTimeGetCurrent();
NSLog(#"Label:%# = %f",label3.text, fetchTime - currentTime);
currentTime = CFAbsoluteTimeGetCurrent();
UILabel *label4 = (UILabel *)[self.view viewWithTag:5000];
fetchTime = CFAbsoluteTimeGetCurrent();
NSLog(#"Label:%# = %f",label4.text, fetchTime - currentTime);
currentTime = CFAbsoluteTimeGetCurrent();
UILabel *label5 = (UILabel *)[self.view viewWithTag:10000];
fetchTime = CFAbsoluteTimeGetCurrent();
NSLog(#"Label:%# = %f",label5.text, fetchTime - currentTime);
currentTime = CFAbsoluteTimeGetCurrent();
UILabel *label6 = (UILabel *)[self.view viewWithTag:30000];
fetchTime = CFAbsoluteTimeGetCurrent();
NSLog(#"Label:%# = %f",label6.text, fetchTime - currentTime);
And below were the logs (reformatted so that comparison is easy)
Label:5 = 0.000011
Label:100 = 0.000043
Label:1000 = 0.000346
Label:5000 = 0.001169
Label:10000 = 0.002115
Label:30000 = 0.000009
Conclusion:
The viewWithTag: will take more time for higher tags (only if there are large number of objects), it might be possible that search is linear which I think is the case because view.subViews gives you the array in the order they are added not by the tag. Yes it takes more time and it almost work as linear search.
The time depends upon the index at which subview was added, in the above case time for 30000 tag is minimum than all other tags because it was added at first index.
The posible implementation of viewWithTag: could be like this
- (UIView *)viewWithTag:(NSInteger)tag {
for (UIView *view in self.subviews) {
if (view.tag == tag) {
return view;
}
}
return nil;
}