This class is used to customize the behavior of NSDecimalNumber-based arithmetic without having to subclass. In particular, NSDecimalNumberHandler allows clients to specify how NSDecimalNumber objects should handle rounding and errors.

@interface NSDecimalNumberHandler : NSObject <NSCoding, NSDecimalNumberBehaviors>
// Initializers
- (id)initWithRoundingMode:(NSRoundingMode)roundingMode scale:(short)scale raiseOnExactness:(BOOL)exact raiseOnOverflow:(BOOL)overflow raiseOnUnderflow:(BOOL)underflow raiseOnDivideByZero:(BOOL)divideByZero;
// Class Methods
+ (id)decimalNumberHandlerWithRoundingMode:(NSRoundingMode)roundingMode scale:(short)scale raiseOnExactness:(BOOL)exact raiseOnOverflow:(BOOL)overflow raiseOnUnderflow:(BOOL)underflow raiseOnDivideByZero:(BOOL)divideByZero;
+ (id)defaultDecimalNumberHandler;
// Methods Implementing NSCoding
- (void)encodeWithCoder:(NSCoder *)aCoder;
- (id)initWithCoder:(NSCoder *)aDecoder;
// Methods Implementing NSDecimalNumberBehaviors
- (NSRoundingMode)roundingMode;
- (short)scale;
- (NSDecimalNumber *)exceptionDuringOperation:(SEL)operation error:(NSCalculationError)error leftOperand:(NSDecimalNumber *)leftOperand rightOperand:(NSDecimalNumber *)rightOperand;