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The Function of 'super' in Solidity

In Solidity, the 'super' keyword is used to call functions or access state variables of parent contracts. It was introduced in Solidity version 0.6.0 as a replacement for the 'this' keyword when calling parent contract functions.

What is 'super' used for?

The 'super' keyword is used in the following scenarios:

  • Calling functions of parent contracts: When a contract inherits from another contract, it can use the 'super' keyword to call functions of the parent contract.
  • Accessing state variables of parent contracts: 'super' can also be used to access state variables of parent contracts.

Example of using 'super' to call a parent contract function


pragma solidity ^0.8.0;

contract ParentContract {
    function parentFunction() public pure returns (string memory) {
        return "This is the parent function";
    }
}

contract ChildContract is ParentContract {
    function childFunction() public pure returns (string memory) {
        return super.parentFunction();
    }
}

In the above example, the 'ChildContract' contract inherits from the 'ParentContract' contract and uses the 'super' keyword to call the 'parentFunction' of the 'ParentContract' contract.

Example of using 'super' to access a parent contract state variable


pragma solidity ^0.8.0;

contract ParentContract {
    uint public parentVariable;

    constructor() public {
        parentVariable = 10;
    }
}

contract ChildContract is ParentContract {
    function childFunction() public view returns (uint) {
        return super.parentVariable;
    }
}

In the above example, the 'ChildContract' contract inherits from the 'ParentContract' contract and uses the 'super' keyword to access the 'parentVariable' state variable of the 'ParentContract' contract.

Best practices for using 'super'

Here are some best practices to keep in mind when using the 'super' keyword:

  • Use 'super' only when necessary: 'super' should be used only when you need to call a function or access a state variable of a parent contract.
  • Avoid using 'super' in constructors: 'super' should not be used in constructors, as it can lead to unexpected behavior.

Conclusion

In conclusion, the 'super' keyword in Solidity is used to call functions or access state variables of parent contracts. It is a powerful tool that allows for more flexibility and modularity in contract design. However, it should be used judiciously and only when necessary.

Frequently Asked Questions

Q: What is the purpose of the 'super' keyword in Solidity?

A: The 'super' keyword is used to call functions or access state variables of parent contracts.

Q: Can 'super' be used in constructors?

A: No, 'super' should not be used in constructors, as it can lead to unexpected behavior.

Q: Can 'super' be used to call functions of sibling contracts?

A: No, 'super' can only be used to call functions of parent contracts, not sibling contracts.

Q: Is 'super' a replacement for the 'this' keyword?

A: Yes, 'super' is a replacement for the 'this' keyword when calling parent contract functions.

Q: Can 'super' be used to access state variables of sibling contracts?

A: No, 'super' can only be used to access state variables of parent contracts, not sibling contracts.

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