Inheritance in Solidity

virtual invites an override; super reaches the parent.

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.24;

// virtual invites an override; super reaches the parent's code.
contract Gate {
    event Opened(address by);

    function open() public virtual {
        emit Opened(msg.sender);
    }
}

contract LockedGate is Gate {
    bool public unlocked;

    function unlock() external {
        unlocked = true;
    }

    function open() public override {
        require(unlocked, "locked");
        super.open();
    }
}

How it works

1. function open() public virtual may be replaced.
2. override is mandatory spelling on the replacement.
3. super.open() still runs the parent's logging.

Keywords and builtins used here

• address
• bool
• contract
• emit
• event
• external
• function
• is
• public
• require
• true

The run, in numbers

Lines

24

Characters to type

411

Tokens

73

Three-star pace

60 tpm

At the three-star pace of 60 tokens a minute, this run takes about 73 seconds.

Type this snippet

Step 1 of 4 in Composition, step 17 of 28 in Language basics.

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Inheritance in other languages

• C#
• Java
• Visual Basic