objective-c – 非字母数字字符可以用作选择器吗？

#import <Foundation/Foundation.h>
#import <objc/runtime.h>
#import <objc/message.h>

@interface Integer : NSObject
{
    NSInteger   intValue;
}

@property (assign) NSInteger intValue;

@end

@implementation Integer

@synthesize intValue;

- (id) plus:(Integer*)anInteger
{
    Integer* outInt = [Integer new];
    [outInt setIntValue: intValue + [anInteger intValue]];
    return outInt;
}

@end


int main (int argc,char const *argv[])
{
    id pool = [[NSAutoreleasePool alloc] init];

    SEL plusSel = sel_registerName("+");
    Method m = class_getInstanceMethod([Integer class],@selector(plus:));
    class_addMethod([Integer class],plusSel,method_getImplementation(m),method_getTypeEncoding(m));

    Integer* i4 = [Integer new];
    Integer* i20 = [Integer new];
    [i4 setIntValue: 4];
    [i20 setIntValue: 20];

    Integer* res = objc_msgSend(i4,i20);

    NSLog(@"%d + %d = %d",[i4 intValue],[i20 intValue],[res intValue]);
    //  >> 4 + 20 = 24

    [pool drain];
    return 0;
}

除了“哎呀”之外,还有理由对这样做持谨慎态度吗？