Check if NSDecimalNumber is whole number

问题

What's the easiest way to check if an instance of NSDecimalNumber is a whole number?

Thanks!

回答1:

@interface NSDecimalNumber (IsIntegerNumber)
@property (readonly) BOOL isIntegerNumber;
@end

@implementation NSDecimalNumber (IsIntegerNumber)
-(BOOL)isIntegerNumber {
    NSDecimalValue value = [self decimalValue];
    if (NSDecimalIsNotANumber(&value)) return NO;
    NSDecimal rounded;
    NSDecimalRound(&rounded, &value, 0, NSRoundPlain);
    return NSDecimalCompare(&rounded, &value) == NSOrderedSame;
}
@end

回答2:

Subtract the whole number from the decimal number. If the difference is zero then the decimal number is a whole number.

// testVal is NSDecimalNumber
NSString *test = [testVal stringValue];
int intVal = [test intValue];
double doubleVal = [test doubleValue];
if(doubleVal-intVal == 0){
    NSLog(@"Whole number!");
}

Or, get the whole number and compare to the original value:

if(intVal == doubleVal){
    NSLog(@"Whole number!");
}

回答3:

This should work.

Beware of using methods that convert NSDecimalNumber into double.

NSDecimalNumber* input = [...];

NSDecimal roundedDecimal;
NSDecimalRound(&roundedDecimal, [input decimalValue], 0, NSRoundPlain);

NSDecimalNumber* roundedNumber = [NSDecimalNumber decimalNumberWithDecimal:roundedDecimal];

BOOL inputIsWholeNumber = [input isEqualToNumber:roundedNumber];

You should also check for NaN values.

回答4:

Can you not use if ((number % 1) == 0)

回答5:

@implementation NSDecimalNumber (isWholeNumber)
-(BOOL)isWholeNumber
{
    double x = [self doubleValue]; //The approximate value of the receiver as a double.
    double y = floor (x);
    if(fabs(x - y) < DBL_EPSILON)
      return YES;
    return NO;
}
@end  
// [myDecNumber isWholeNumber];

回答6:

Not sure why, but for some reason I was unable to get Jody Hagins' or Sulthan's solutions to work so I went a slightly different way:

-(BOOL)isWholeNumber:(NSDecimalNumber *)number {
    NSDecimalNumber *input = number;

    NSDecimalNumberHandler *handler = [NSDecimalNumberHandler decimalNumberHandlerWithRoundingMode:NSRoundPlain
                                                                                             scale:0
                                                                                  raiseOnExactness:NO
                                                                                   raiseOnOverflow:NO
                                                                                  raiseOnUnderflow:NO
                                                                               raiseOnDivideByZero:NO];

    NSDecimalNumber *vOne = [NSDecimalNumber decimalNumberWithString:@"1"];

    NSDecimalNumber *result = [number decimalNumberByMultiplyingBy:vOne
                                                      withBehavior:handler];

    BOOL inputIsWholeNumber = [input isEqualToNumber:result];

    return inputIsWholeNumber;
}

回答7:

Try this, you can skip first line, i just used it to create a NSDecimalNumber object

NSDecimalNumber  *decNumb=[NSDecimalNumber decimalNumberWithString:@"20.5"];//try with just 20
NSString* str=[NSString stringWithFormat:@"%@",decNumb];

if ([str rangeOfString:@"."].location==NSNotFound && [str rangeOfString:@"-"].location==NSNotFound) {
    NSLog(@"it is whole number");
} 
else
    NSLog(@"it is not whole number");

来源：https://stackoverflow.com/questions/12298755/check-if-nsdecimalnumber-is-whole-number

标签

iphone

objective-c

ios

nsdecimalnumber