NSNumberFormatter to stop shortening numbers - objective-c

Question

EDIT: Fixed, here is how i did it for furture reference:
NSNumber *inputNumber = [[NSNumber alloc ]initWithDouble:convertValue];
NSNumber *resultNumber = [[NSNumber alloc]initWithDouble:result];
NSNumberFormatter *formatterResult = [[NSNumberFormatter alloc] init];
formatterResult.numberStyle = NSNumberFormatterDecimalStyle;
NSNumberFormatter *formatterInput = [[NSNumberFormatter alloc] init];
formatterInput.numberStyle = NSNumberFormatterDecimalStyle;
[formatterResult setNumberStyle:NSNumberFormatterDecimalStyle];
[formatterResult setMaximumFractionDigits:6];
[formatterInput setNumberStyle:NSNumberFormatterDecimalStyle];
[formatterInput setMaximumFractionDigits:6];
//These four lines are the one fixing the issue.
NSString *formattedResultString = [formatterResult stringFromNumber:(NSNumber*)resultNumber];
NSString *formattedInputString = [formatterInput stringFromNumber:(NSNumber*)inputNumber];
NSString *formelString = [[NSString alloc]initWithFormat:
#" %# %# =", formattedInputString, convertFromName];
formelLabel.text = formelString;
NSString *resultString = [[NSString alloc]initWithFormat:
#" %# %#",formattedResultString, convertToName];
resultLabel.text = resultString;
----------ORIGINAL QUESTION------------
So I have a problem with NSNumberFormatter shortening numbers too much, and also not displaying decimals when the main number is over 8 digits.
Problem described in following picture:
<- Working, but shortening to three decimals. (And rounding up, which is done mathematically correct)
And then the problems: (Right-most picture is correct)
As you can see, the bottom image just ignores the decimals completely. What code do I need to add/change for this to work properly?
Here is the relevant code:
[super viewDidLoad];
_convertFrom = #[#"MTPA", #"MMcf/day",
#"Mill.Sm3/day", #"MMBTU/day", #"Boe/day",#"ton LNG/day", #"GJ/day"];
_convertTo = #[#"MTPA", #"MMcf/day",
#"Mill.Sm3/day", #"MMBTU/day", #"Boe/day", #"ton LNG/day", #"GJ/day"];
_convertRates = #[ #1.0f, #133.3333333f, #3.775579545f,
#137333.3333f, #23747.68013, #1716.17252, #147247.6022];
//some place down in the code:
-(void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component
{
[self updateConversionLabel];
}
- (void)updateConversionLabel
{
float convertFrom = [[_convertRates objectAtIndex:[picker selectedRowInComponent:0]] floatValue];
float convertTo = [[_convertRates objectAtIndex:[picker selectedRowInComponent:1]] floatValue];
NSNumberFormatter *fmt = [NSNumberFormatter new];
float input = [fmt numberFromString:inputText.text].floatValue;
float to = convertTo;
float from = convertFrom;
float convertValue = input;
float relative = to / from;
float result = relative * convertValue;
NSString *convertFromName = [_convertFrom objectAtIndex:[picker selectedRowInComponent:0]];
NSString *convertToName = [_convertFrom objectAtIndex:[picker selectedRowInComponent:1]];
NSNumber *inputNumber = [[NSNumber alloc ]initWithFloat:convertValue];
NSNumber *resultNumber = [[NSNumber alloc]initWithFloat:result];
NSNumberFormatter *formatterResult = [[NSNumberFormatter alloc] init];
formatterResult.numberStyle = NSNumberFormatterDecimalStyle;
NSNumberFormatter *formatterInput = [[NSNumberFormatter alloc] init];
formatterInput.numberStyle = NSNumberFormatterDecimalStyle;
NSString *formattedResultString = [formatterResult stringFromNumber:(NSNumber*)resultNumber];
NSString *formattedInputString = [formatterInput stringFromNumber:(NSNumber*)inputNumber];
NSString *formelString = [[NSString alloc]initWithFormat:
#" %# %# =", formattedInputString, convertFromName];
formelLabel.text = formelString;
NSString *resultString = [[NSString alloc]initWithFormat:
#" %# %#",formattedResultString, convertToName];
resultLabel.text = resultString;
}
I'd assume the problem/fix is in this code.

Answer 1

EDIT: Fixed, here is how I did it for future reference:
NSNumber *inputNumber = [[NSNumber alloc ]initWithDouble:convertValue];
NSNumber *resultNumber = [[NSNumber alloc]initWithDouble:result];
NSNumberFormatter *formatterResult = [[NSNumberFormatter alloc] init];
formatterResult.numberStyle = NSNumberFormatterDecimalStyle;
NSNumberFormatter *formatterInput = [[NSNumberFormatter alloc] init];
formatterInput.numberStyle = NSNumberFormatterDecimalStyle;
[formatterResult setNumberStyle:NSNumberFormatterDecimalStyle];
[formatterResult setMaximumFractionDigits:6];
[formatterInput setNumberStyle:NSNumberFormatterDecimalStyle];
[formatterInput setMaximumFractionDigits:6];
//These four lines are the one fixing the issue.
NSString *formattedResultString = [formatterResult stringFromNumber: (NSNumber*)resultNumber];
NSString *formattedInputString = [formatterInput stringFromNumber:(NSNumber*)inputNumber];
NSString *formelString = [[NSString alloc]initWithFormat:
#" %# %# =", formattedInputString, convertFromName];
formelLabel.text = formelString;
NSString *resultString = [[NSString alloc]initWithFormat:
#" %# %#",formattedResultString, convertToName];
resultLabel.text = resultString;

Answer 2

Real arithmetic is precise. Any computer arithmetic has limited range - how many digits can be represented; and in the case of fractions inaccuracies due to the use of decimal factions by us humans and binary fractions by computers.
In your code you are using float which is a 32-bit binary floating point number with an precision of around 6 decimal digits and a range roughly from 10^-38 to 10^38. Your numbers are up to 9 digits.
Try using double thoughtout (and doubleValue etc.) which is a 64-bit binary floating point with a precision of around 15 decimal digits. You may still find the numbers don't come out as you wish, and for that you will need to look more into how to format numbers, but you should get the precision you are after.
If you need more precision, and decimal floating point as well, look at NSDecimalNumber.
See 32-bit floating point and 64-bit floating point for more details.