How to check an object's type in C++/CLI?

Question

Is there a simple way to check the type of an object? I need something along the following lines:

MyObject^ mo = gcnew MyObject();
Object^ o = mo;

if( o->GetType() == MyObject )
{
    // Do somethine with the object
}
else
{
    // Try something else
}

At the moment I'm using nested try-catch blocks looking for System::InvalidCastExceptions which feels ugly but works. I was going to try and profile something like the code above to see if it's any faster/slower/readable but can't work out the syntax to even try.

In case anyone's wondering, this comes from having a single queue entering a thread which supplied data to work on. Occasionally I want to change settings and passing them in via the data queue is a simple way of doing so.

score 28 · Accepted Answer · answered Mar 11 '10 at 09:51

28

You can use MyObject::typeid in C++/CLI the same way as typeof(MyObject) is used in C#. Code below shamelessly copied from your question and modified ...

MyObject^ mo = gcnew MyObject();
Object^ o = mo;

if( o->GetType() == MyObject::typeid )
{
    // Do somethine with the object
}
else
{
    // Try something else
}

answered Mar 11 '10 at 09:51

mcdave

2,450
15
21

1

It still works in VS2010. I don't have VS2012 so can't comment on the latest VS version. It may be you are not "seeing that typeid member" because autocomplete for C++/CLI was not included in VS2010. – mcdave Sep 12 '12 at 15:00
I could even use it in VS2013. – Ozair Kafray Apr 20 '18 at 07:37

score 9 · Answer 2 · answered Mar 09 '10 at 16:43

9

You should check out How to: Implement is and as C# Keywords in C++:

This topic shows how to implement the functionality of the is and as C# keywords in Visual C++.

answered Mar 09 '10 at 16:43

Andrew Hare

320,708
66
621
623

Is there a way to do that with generics rather than templates so that the method can be used in external assemblies? – Jon Cage Mar 10 '10 at 11:14

mfperzel · Answer 3 · 2010-03-09T18:15:08.800

edit: I will leave this here. But this answer is for C++. Probably not even slightly related to doing this for the CLI.

You need to compile with RTTI(Run Time Type Information) on. Then look at the wikipedia article http://en.wikipedia.org/wiki/Run-time_type_information and search google for RTTI. Should work for you.

On the other hand you might want to have a virtual base class for all your data classes with a member variable that describes what type it is.

How to check an object's type in C++/CLI?

3 Answers3

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