Question

Is there a way to pass a variable for the floating point precision parameter in printf-style string formatting functions in Objective-C (or even C)? For example, in TCL and other scripting languages, I can do something like this:

set precision 2
puts [format "%${precision}f" 3.14159]

and the output will be, of course, 3.14. I would like to do something similar in Objective-C:

float precision = 2
NSString *myString = [NSString stringWithFormat:@".2f", 3.14159]

except that I would like to include precision as a variable. How can this be done?

Answer 1

Yes, the string format specifiers for printf, which are used by Cocoa for formatting, include a variable-precision specifier, * placed after the decimal point:

int precision = 3;
NSLog(@"%.*f", precision, 3.14159);
NSString *myString = [NSString stringWithFormat:@".*f", precision, 3.14159];