Author: William Gerbert

Testing if two objects are "related" or "identical" (RTTI)

Answer:

Do you need to know whether object a is of a derived class from the class that 
another object b is of? Or if they may even be of the same class?

The following little code snippet tells it..


1   program dummy;
2   
3   var
4     a, b: TObject;
5   
6   begin
7     // some code to assign the pointers
8     // ...
9   
10    // now evaluate the RTTI of two instantiated objects
11    if a is b then
12      ShowMessage('a is derived from b or same class');
13  
14    if a.classtype = b.classtype then
15      ShowMessage('a and b are of the same class');
16  
17    // alternative to ClassType comparison (slower!)
18    if a.ClassName = b.ClassName then
19      ShowMessage('a and b are of the same class')
20  end.