Error when trying to dynamic_cast<> a reference of a variable

[johnnyICON]

Hi, I am trying to create a function that compare's two objects.

Here, take a look:

int Integer::compareTo(const NodeItem &anotherNodeItem)
{
    int returnCode = 0;
    
    Integer *otherInteger = dynamic_cast<Integer&>(anotherNodeItem);

    if (otherInteger == NULL)
        returnCode = ERROR_INCOMPATIBLE_TYPES;
    else
        returnCode = compareTo(*otherInteger);

    delete otherInteger;

    return returnCode;
}

The error I get when I try to compile is at this statement:

Integer *otherInteger = dynamic_cast<Integer&>(anotherNodeItem);

The error is this:
Integer.cpp(54): error C2682: cannot use dynamic_cast to convert from 'const NodeItem' to 'Integer &'

I'm not too sure of another way of doing this, but basically I want the function to be able to take a NodeItem pointer, and check whether the NodeItem is an Integer by using dynamic_cast and testing for a NULL result.

Thanks for the help in advance.

[Ajay Vijay]

First

Integer *otherInteger = dynamic_cast<Integer&>(anotherNodeItem);

'&' should be '*'
Second, please tell what's the relation between NodeItem and Integer types?

[johnnyICON]

An Integer is a NodeItem.

A NodeItem is an abstract class for any piece of data that is in a node.

[johnnyICON]

Integer *otherInteger = dynamic_cast<Integer*>(anotherNodeItem);

error C2682: cannot use dynamic_cast to convert from 'const NodeItem' to 'Integer *'

[Graham]

Point 1: you can't remove constness with dynamic_cast: you will need to cast to const Integer&

Point 2: you're trying to assign it to a pointer to integer. Either change the variable declaration to const Integer& or change the cast to dynamic_cast<const Integer *>(&anotherNodeItem) (and make the variable const).

[johnnyICON]

Thanks, it worked.

const Integer *otherInteger = dynamic_cast<const Integer*>(&anotherNodeItem);

[johnnyICON]

Something I didn't notice, but there is a warning message with that comes with that statment:

warning C4541: 'dynamic_cast' used on polymorphic type 'NodeItem' with /GR-; unpredictable behavior may result

I'm just wondering if it means anything other than what I can understand as unpredictable behaviour.

[Kheun]

See MSDN. You have to turn on RTTI in order to use dynamic_cast<>.