Difference of building JSON...

New JSONKit.m

isClass = [object PSYJK_JSONClass];
    
    if(isClass == PSYJKClassUnknown

Old JSONKit.m

if(JK_EXPECT_T(object->isa == encodeState->fastClassLookup.stringClass))     { isClass = JKClassString;     }
  else if(JK_EXPECT_T(object->isa == encodeState->fastClassLookup.numberClass))     { isClass = JKClassNumber;     }
  else if(JK_EXPECT_T(object->isa == encodeState->fastClassLookup.dictionaryClass)) { isClass = JKClassDictionary; }
  else if(JK_EXPECT_T(object->isa == encodeState->fastClassLookup.arrayClass))      { isClass = JKClassArray;      }
  else if(JK_EXPECT_T(object->isa == encodeState->fastClassLookup.nullClass))       { isClass = JKClassNull;       }
  else {
         if(JK_EXPECT_T([object isKindOfClass:[NSString     class]])) { encodeState->fastClassLookup.stringClass     = object->isa; isClass = JKClassString;     }
    else if(JK_EXPECT_T([object isKindOfClass:[NSNumber     class]])) { encodeState->fastClassLookup.numberClass     = object->isa; isClass = JKClassNumber;     }
    else if(JK_EXPECT_T([object isKindOfClass:[NSDictionary class]])) { encodeState->fastClassLookup.dictionaryClass = object->isa; isClass = JKClassDictionary; }
    else if(JK_EXPECT_T([object isKindOfClass:[NSArray      class]])) { encodeState->fastClassLookup.arrayClass      = object->isa; isClass = JKClassArray;      }
    else if(JK_EXPECT_T([object isKindOfClass:[NSNull       class]])) { encodeState->fastClassLookup.nullClass       = object->isa; isClass = JKClassNull;       }
    else {

This is the additional magic methods.m

@interface NSObject (PSYJKClassAdditions)
- (PSYJKClass)PSYJK_JSONClass;
@end

@implementation NSObject (PSYJKClassAdditions)
- (PSYJKClass)PSYJK_JSONClass; { return PSYJKClassUnknown; }
@end

@implementation NSString (PSYJKClassAdditions)
- (PSYJKClass)PSYJK_JSONClass; { return PSYJKClassString; }
@end

@implementation NSDictionary (PSYJKClassAdditions)
- (PSYJKClass)PSYJK_JSONClass; { return PSYJKClassDictionary; }
@end

@implementation NSNull (PSYJKClassAdditions)
- (PSYJKClass)PSYJK_JSONClass; { return PSYJKClassNull; }
@end

@implementation NSArray (PSYJKClassAdditions)
- (PSYJKClass)PSYJK_JSONClass; { return PSYJKClassArray; }
@end

@implementation NSNumber (PSYJKClassAdditions)
- (PSYJKClass)PSYJK_JSONClass; { return PSYJKClassNumber; }
@end