Catching base and derived classes exceptions in C++

To catch an exception for both base and derive class then we need to put catch block of derived class before the base class. Otherwise, the catch block of derived class will never be reached.

Algorithm

Begin
   Declare a class B.
   Declare another class D which inherits class B.
   Declare an object of class D.
   Try: throw derived.
   Catch (D derived)
      Print “Caught Derived Exception”.
   Catch (B b)
      Print “Caught Base Exception”.
End.

Here is a simple example where catch of derived class has been placed before the catch of base class, now check the Output

#include<iostream>
using namespace std;
class B {};
class D: public B {}; //class D inherit the class B
int main() {
   D derived;
   try {
      throw derived;
   }
   catch(D derived){
      cout<<"Caught Derived Exception"; //catch block of derived class
   }
   catch(B b) {
      cout<<"Caught Base Exception"; //catch block of base class
   }
   return 0;
}

Output

Caught Derived Exception

Here is a simple example where catch of base class has been placed before the catch of derived class, now check the Output

#include<iostream>
using namespace std;

class B {};
class D: public B {}; //class D inherit the class B
int main() {
   D derived;
   try {
      throw derived;
   }
   catch(B b) {
      cout<<"Caught Base Exception"; //catch block of base class
   }
   catch(D derived){
      cout<<"Caught Derived Exception"; //catch block of derived class
   }
   return 0;
}

Output

Caught Base Exception
Thus it is proved that we need to put catch block of derived class before the base class. Otherwise, the catch block of derived class will never be reached.

karthikeya Boyini

Updated on: 30-Jul-2019

1K+ Views

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