Cocoa how to display float value with one decimal values without round off

Question

I have a floating point value, but when i need to represent to the user I need it to show to one decimal place, without rounding off. so basically i need to truncate to up to one decimal place. for example 95.56 -> 95.5

[find answer here][1] [1]: http://stackoverflow.com/questions/560517/how-to-set-the-float-value-to-two-decimal-number-in-objective-c — Saqib Saud, Feb 16 '12 at 07:03
@SaqibSaud, all these answer in that page will round off the value, but i dont want to round off — cocoaNoob, Feb 16 '12 at 07:29

justin · Answer 1 · 2012-02-16T07:41:58.120

6

NSNumberFormatter will do this for you.

-setMaximumFractionDigits: -setRoundingMode:

Update

#import <Foundation/Foundation.h>

int main(int argc, const char * argv[]) {
  @autoreleasepool {
    NSNumberFormatter * nf = [[NSNumberFormatter new] autorelease];
    [nf setMaximumFractionDigits:1];
    [nf setRoundingMode:NSNumberFormatterRoundFloor];
    NSLog(@"The number is '%@'", [nf stringFromNumber:[NSNumber numberWithDouble:95.56]]);
  }
  return 0;
}

Yields:

2012-02-16 02:39:49.799 NumberFormatter[14592:903] The number is '95.5'

edited Feb 16 '12 at 07:41

answered Feb 16 '12 at 07:05

justin

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wat should is set in rounding mode – cocoaNoob Feb 16 '12 at 07:26
95.56 to 95.5 would use `NSNumberFormatterRoundFloor` – justin Feb 16 '12 at 07:30
but with this I am getting 95.6 – cocoaNoob Feb 16 '12 at 07:31
are you sure? that would be a bug (unless another trait is interfering) – justin Feb 16 '12 at 07:31
(In response to deleted response) At your suggestion, I did try it myself. It worked as I expected. See the update. – justin Feb 16 '12 at 07:42
sorry my mistake, it works like a charm, thank you, can u care to explain me the explaination, what is going on in behind – cocoaNoob Feb 16 '12 at 07:44
you're welcome. There are a few rounding modes -- `NSNumberFormatterRoundFloor ` rounds similar to the C math function `floor(double)` *however* the formatter will scale the argument for the fraction digits. – justin Feb 16 '12 at 07:46
but this approach has one problem if value is 16.8, then it will give result 16.7 – cocoaNoob Feb 17 '12 at 07:25
that's floating point behavior in C languages! - a floating point number is not a string, and it's not exact. if you `printf` a `float` representing `16.8`, you may see `16.799999`. `floor` that memory representation, and you have `16.7`. – justin Feb 17 '12 at 08:35
ok, so finally i have to use string conversion logic only then – cocoaNoob Feb 17 '12 at 08:50

score 5 · Answer 2 · answered Feb 16 '12 at 07:15

5

try out with this example

float t = 25.55;
NSLog(@"%.1f", t);

it shows 25.5 if you set %.2f you get 25.55

answered Feb 16 '12 at 07:15

Hiren

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if here t =25.56, then it shows 25.6, rather i want to show 25.5 only – cocoaNoob Feb 16 '12 at 07:27

score 1 · Accepted Answer · answered Feb 16 '12 at 12:49

1

It should be like this

sudo code

convert number to string.

find "." in string.

make a substring from start to "." position +1

answered Feb 16 '12 at 12:49

Saqib Saud

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Even I was thinking that way, but number formatter is better solution, and performance wise is better compare to string manipulation – cocoaNoob Feb 17 '12 at 05:38

Cocoa how to display float value with one decimal values without round off

3 Answers3