.Net developer new to Objective-C. Need some critique and suggestions - objective-c

Question

I've created one of my first apps using Objective-C. Being a noob, there's a lot of stuff I want to do, but don't know how to apply it in Objective-C. Please take a look at the method below (which I created from scratch) and tell me what you would do to make it better. Obviously I've duplicated code across 2 UILabels, but I'd like to simplify that (I hate duplicating code) but I'm unaware what the best way to do it is. I just need suggestions which will help me better understand the right way to do stuff in Objective-C
timeText and dateText are of type UILabel
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
if (isRearranging)
{
NSLog(#"touchesMoved");
NSLog(#"touches=%#,event=%#",touches,event);
//TOUCH INFO
UITouch *touch = [[touches allObjects] objectAtIndex:0];
CGPoint currentLocation = [touch locationInView:touch.view];
CGPoint previousLocation = [touch previousLocationInView:touch.view];
//FRAME INFO
float timeHalfWidth = timeText.frame.size.width / 2;
float timeHalfHeight = timeText.frame.size.height / 2;
CGRect timeTextRect = CGRectMake(timeText.center.x - (timeHalfWidth), timeText.cener.y - (timeHalfHeight), timeText.frame.size.width, timeText.frame.size.height);
float dateHalfWidth = dateText.frame.size.width / 2;
float dateHalfHeight = dateText.frame.size.height / 2;
CGRect dateTextRect = CGRectMake(dateText.center.x - (dateHalfWidth), dateText.center.y - (dateHalfHeight), dateText.frame.size.width, dateText.frame.size.height);
//IF TIME TEXT
if(CGRectContainsPoint(timeTextRect,previousLocation))
{
CGPoint item = timeText.center;
CGPoint diff;
diff.x = previousLocation.x - item.x;
diff.y = previousLocation.y - item.y;
CGPoint newLoc;
newLoc.x = currentLocation.x - diff.x;
newLoc.y = currentLocation.y - diff.y;
if (newLoc.x<timeHalfWidth)
newLoc.x = timeHalfWidth;
if (newLoc.y<timeHalfHeight)
newLoc.y = timeHalfHeight;
[timeText setCenter:(newLoc)];
}
//IF DATE TEXT
if(CGRectContainsPoint(dateTextRect,previousLocation))
{
CGPoint item = dateText.center;
CGPoint diff;
diff.x = previousLocation.x - item.x;
diff.y = previousLocation.y - item.y;
CGPoint newLoc;
newLoc.x = currentLocation.x - diff.x;
newLoc.y = currentLocation.y - diff.y;
if (newLoc.x<dateHalfWidth)
newLoc.x = dateHalfWidth;
if (newLoc.y<dateHalfHeight)
newLoc.y = dateHalfHeight;
[dateText setCenter:(newLoc)];
}
}
touchMoved = YES;
}
Thanks so much for your help!

Answer 1

A first step, independent from the language you are working in, would be to follow DRY - most of your code is the same for both labels.
Then there is already functionality for hit-testing in the SDK, e.g. -hitTest:withEvent: or -pointInside:withEvent::
NSArray *labels = [NSArray arrayWithObjects:timeText, dateText, nil];
for (UILabel *label in labels) {
if ([label pointInside:previousLocation withEvent:nil]) {
[self relocateLabel:label];
break;
}
}

Answer 2

I will answer an additional question posed by asker in a comment. Quote:
What if I wanted to use mixed types in that array? i.e. a couple UILabel and a couple UIImageView. Is there a way to compare types or use generics? This is a poor guess/example for (NSObject *obj in objects) { if (label.type==UILabel) [self relocateLabel:obj]; else if (label.type==UIImageView) [self relocateImage:obj]; }
As Georg Fritzsche answered there, Objective-C messaging is dynamic. Object will be "queried" if it supports that message at runtime, and if so, it will execute the method associated with the message. Method/message name is called a "selector".
If you explicitly want to figure out object's class, you can do that as well.
if([view isKindOfClass:[UILabel class]])
{
// your code here
}
If you just want to figure out if the target object responds to a selector (that is, implements a method):
if([view respondsToSelector:#selector(relocateView:)])
{
// your code here
}
Selectors are derived from method names by omitting arguments themselves, leaving colons intact and appending everything closely. For example, if you had a message send (that is, method call): [thing moveTowardsObject:door movementType:XYZ_CRAWL], its selector would be: moveTowardsObject:movementType: and you'd get it using #selector(moveTowardsObject:movementType:).
In a loop such as what Georg posted, you typically want to just check if the target object responds to a selector, since otherwise an exception would be thrown, and Objective-C code rarely catches exceptions as part of a normal code flow (as opposed to what Python developers do).