Dynamic Type Information

This snippet will show you how to get type information of an instance in your code at runtime. You will be able to know the name of the type of a variable.

The operator you need is typeid(expression). expression is a variable you want to get information about. typeid will return a constant reference to a type_info object that holds info about the given instance. Here's the definition:

class type_info {
public:
  virtual ~type_info();
  int operator==(const type_info& rhs) const;
  int operator!=(const type_info& rhs) const;
  int before(const type_info& rhs) const;
  const char* name() const;
  const char* raw_name() const;
private:
  ...
};

Remember that you have to include typeinfo.h before using typeid/type_info. Using this operator is very easy. The class type_info also supports comparison so you can compare two variables dynamically. You could check whether they have the same type or not.

Here is a little example how to use it:

#include &lt;iostream.h&gt;
#include &lt;typeinfo.h&gt;
//any user class
#include "MyClass.h" 
 
int main()
{
   char test;
   char test2;
   MyClass myClass;
 
   cout &lt;&lt; "Type of test: " &lt;&lt; typeid(test).name() &lt;&lt; endl;
   cout &lt;&lt; "Type of test and test2 are the same: " &lt;&lt;
                              (typeid(test) == typeid(test2))
        &lt;&lt; endl;
   cout &lt;&lt; "Dynamic type name of myClass: " &lt;&lt; typeid(myClass).name()
        &lt;&lt; endl;
 
   return 0;
}

Output of this application:

Type of test: char
Type of test and test2 are the same: 1
Dynamic type name of myClass: class MyClass

Not very difficult, isn't? This operator works for everything, for pointers, references.. If you have problems, m@il me. Happy Coding!

[ Dynamic Type Information ]