ios class

//You will get a Class by sending class method class to a class
if [obj isKindOfClass:[NSString class]]{  
    [obj ...];
}else if([obj respondsToSelect:@selector(shoot:)]){ //no matter what obj is
    [obj shoot];                                    // if obj has shoot method ,it can be excuted  
}

//SEL is a type
SEl shootSelecor = @selector(shoot:);