Most efficient way to manage formatted strings for constantly updated UIlabels in Xcode

Question

I have a UILabel in an interactive calculator application that is continually being refreshed with a newly formatted message as the user changes a UISlider value. My question is what is the most efficient way to manage the strings:

NSString *data = [[NSString *alloc] initWithFormat:@"Value A: %0.1f, Value B: %0.1f, valueA,valueB];
myUILabel.text = data;
[data release];

or

[myMutableString setString:@""];
[myMutableString appendFormat:@"Value A: %0.1f, Value B: %0.1f, valueA,valueB];
myUILabel.text = myMutableString;

Any advice would be appreciated

Answer 1

As the string is there to be read by the user and so has to remain visible for a time I doubt that the speed of the format matters as it will take much less time than it takes for a user to read the value.

Answer 2

Creating a single, non-mutable string (your first example) is going to be more efficient than creating and then modifying a mutable string.

However the real answer is that it doesn't matter. The amount of time is negligible in user interaction terms, and any temporary objects created as a side effect will be freed on every pass through the event loop anyway, so worrying about this at all is premature optimization.