Limiting both the fractional and total number of digits when formatting a float for display

Question

I need to print a float value in area of limited width most efficiently. I\'m using an NSNumberFormatter, and I set two numbers after the decimal point as the d

Answer 1

Here is how I implemented this in my code. I don't know how efficient it is, I hope not bad.

So I create a global NSNumberFormatter

NSNumberFormatter* numFormatter; 

and initialize it somewhere:

numFormatter=[[NSNumberFormatter alloc]init];

Then I format number with the following function:

- (NSString*)formatFloat:(Float32)number withOptimalDigits:(UInt8)optimalDigits maxDecimals:(UInt8)maxDecimals
{
    NSString* result;
    UInt8 intDigits=(int)log10f(number)+1;
    NSLog(@"Formatting %.5f with maxDig: %d maxDec: %d intLength: %d",number,optimalDigits,maxDecimals,intDigits);  

    numFormatter.maximumFractionDigits=maxDecimals;
    if(intDigits>=optimalDigitis-maxDecimals) {
        numFormatter.usesSignificantDigits=YES;
        numFormatter.maximumSignificantDigits=(intDigits>optimalDigits)?intDigits:optimalDigits;
    } else {
        numFormatter.usesSignificantDigits=NO;
    }
    result = [numFormatter stringFromNumber:[NSNumber numberWithFloat:number]];

    return result;
}