How can I get the input argument type of a selector?

Question

I'm trying to write a generic XML to Core Data parser using libxml2. Since I have control over both, the XML elements correspond exactly to the objects and the attributes to the properties of the objects. This is all fine and everything works well, except when the attributes are of a type other than NSString. I realize that selectors know nothing of their input types, but is there some other way to determine them? That is, can I generically convert the string to the type needed by the selector, or do I need to write an if-then-else switch somewhere?

Here's my in-progress code:

static void startElementSAX(void *ctx, const xmlChar *localname, const xmlChar *prefix, const xmlChar *URI, 
                            int nb_namespaces, const xmlChar **namespaces, int nb_attributes, int nb_defaulted, const xmlChar **attributes) {
    //set up a local pool so we can release these objects
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

    FormParser *parser = (FormParser *)ctx;
    NSString *elementName = [[NSString alloc] initWithUTF8String:(const char *)localname];

    NSManagedObject *localObject = [parser.managedObjectContext insertNewObjectForEntityForName:elementName];

    // according to http://www.xmlsoft.org/html/libxml-SAX2.html#xmlSAX2StartElementNs,
    // there are 5 parts to the attribute array: localname/prefix/URI/value/end
    int attribCounter;
    for (attribCounter = 0; attribCounter < (nb_attributes * 5); attribCounter++)
    {
        NSString *attributeValue = nil;
        NSString *attributeName = [[NSString alloc] initWithUTF8String:(const char *)attributes[attribCounter]];

       //let's skip over the prefix
        attribCounter++;
        //and the URI
        attribCounter++;
        //and get to the value
        attribCounter++;
        //increment after using counter so we can get the end value
        const char *valueStart = (const char *)attributes[attribCounter++];
        const char *valueEnd = (const char *)attributes[attribCounter];

        //if we have good values, init a value with 
        if (valueStart && valueEnd) {
            attributeValue = [[NSString alloc] initWithBytes:attributes[attribCounter-1] length:(strlen(valueStart) - strlen(valueEnd)) encoding:NSUTF8StringEncoding];
        }

        SEL setAttribute = NSSelectorFromString([NSString stringWithFormat:@"set%@:", [attributeName capitalizedString]]);
        if (attributeValue && [localObject respondsToSelector:setAttribute])
        {
            //HERE'S WHERE I NEED TO CHECK TYPE AND CAST IF NEEDED
            [localObject setValue:attributeValue forKey:attributeName];
        }

    }

    //set parser's current object
    SEL setCurrent = NSSelectorFromString([NSString stringWithFormat:@"setCurrent%@:", [elementName capitalizedString]]);
    if ([parser respondsToSelector:setCurrent])
    {
        [parser performSelector:setCurrent withObject:localObject];
    }

    //set parent
    SEL setParent = NSSelectorFromString(@"setParent");
    if ([localObject respondsToSelector:setParent])
    {
        SEL getParent = NSSelectorFromString([NSString stringWithFormat:@"getCurrent%@", [[parser getElementParent:elementName] capitalizedString]]);
        if ([parser respondsToSelector:getParent])
        {
            [localObject performSelector:setParent withObject:[parser performSelector:getParent]];
        }
    }

    NSError *error = nil;
    if (![parser.managedObjectContext save:&error])
    {
        if (parser.delegate != nil && [parser.delegate respondsToSelector:@selector(parser:didFailWithError:)]) {
            [parser.delegate parser:parser didFailWithError:error];
    }
    }
    [pool release];
}

Answer 1

Kept Googling and found that I can use NSMethodSignature:

- (const char *)getArgumentTypeAtIndex:(NSUInteger)index

Here's the relevant documentation.

Though it does say

This encoding is implementation-specific, so applications should use it with caution.

ETA: Aaand, I'm back to dead end. All I can find out is that it is a Class. I will ask a more specific question.