Notes

• Parent contracts can be called directly, or by using the keyword super.
• By using the keyword super, all of the immediate parent contracts will be called.

Code

solidity
Super.sol
Copy
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

/* Inheritance tree
  A
/  \
B   C
\ /
 D
*/

contract A {
   // This is called an event. You can emit events from your function
   // and they are logged into the transaction log.
   // In our case, this will be useful for tracing function calls.
   event Log(string message);

   function foo() public virtual {
       emit Log("A.foo called");
   }

   function bar() public virtual {
       emit Log("A.bar called");
   }
}

contract B is A {
   function foo() public virtual override {
       emit Log("B.foo called");
       A.foo();
   }

   function bar() public virtual override {
       emit Log("B.bar called");
       super.bar();
   }
}

contract C is A {
   function foo() public virtual override {
       emit Log("C.foo called");
       A.foo();
   }

   function bar() public virtual override {
       emit Log("C.bar called");
       super.bar();
   }
}

contract D is B, C {
   // Try:
   // - Call D.foo and check the transaction logs.
   //   Although D inherits A, B and C, it only called C and then A.
   // - Call D.bar and check the transaction logs
   //   D called C, then B, and finally A.
   //   Although super was called twice (by B and C) it only called A once.

   function foo() public override(B, C) {
       super.foo();
   }

   function bar() public override(B, C) {
       super.bar();
   }
}