Enums

In Solidity, an enum is a user-defined data type that consists of a set of named values. Enums are a way to create a custom type with a finite set of possible values, which can make your code more readable and less error-prone.

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract EnumExample {
    // Define an enum with possible states
    enum State { Waiting, Active, Completed }

    // State variable to store the current state
    State public state;

    // Set the initial state to 'Waiting'
    constructor() {
        state = State.Waiting;
    }

    // Function to set the state to 'Active'
    function activate() public {
        state = State.Active;
    }

    // Function to set the state to 'Completed'
    function complete() public {
        state = State.Completed;
    }

    // Function to check if the state is 'Completed'
    function isCompleted() public view returns (bool) {
        return state == State.Completed;
    }
}

The enum named State is declared with three possible values: Waiting, Active, and Completed.
Enum values are zero-indexed, meaning State.Waiting is 0, State.Active is 1, and State.Completed is 2. You can directly use these values in comparisons and assignments.