Hotel and vending Solidity smart contract

The sample hotel and vending Solidity smart contract below allows one to rent a hotel room. It allows someone to make a payment for a room if the room is vacant. After payment is made to the contract the funds are sent to the owner. This smart contract can be expanded to unlock the door or dispense a key code after payment is made.

Think of this contract like a vending machine. You input funds, validations pass, and you get something in return. It is the same concept as a gumball machine.

Experiment with the contract below and learn the basics of a simple contract. Deploy it to the test network using Remix. Enhance the code and add another function. 

Try it in Remix

pragma solidity ^0.7.6;

//example hotel smart contract

contract HotelRoom {
    //you will learn
    //how to pay smart contracts
    //modifiers
    //events

    //create an emun with 2 status so we can keep track of our hotel room
    enum Statuses { Vacant, Occupied }
    Statuses currentStatus;

    //create an event for others that want to subscribe to events like a smart lock to unlock the door
    event Occupy(address _occupant, uint _value);


    //state variable is written to the block chain.  Address to pay owner is the creator of the contract
    address payable public owner;

    // constructor is called once when the contract is created.  person who deployed this contract to the block chain is the owner
    constructor() public {
        owner = msg.sender;
        currentStatus = Statuses.Vacant;
    }

    //solidity has a concept of requirements that you can set.  example don't allow someone to book the hotel room if it not vacant or prevent them from paying twice
    modifier onlyWhileVacant{
         //check status.  Require checks to see if it is true then continue if not it is false it will halt and displays error message
        require(currentStatus == Statuses.Vacant, "Currently Occupied");
        _;
    }
    // this modifier allows you to pass in an amount
    modifier costs (uint _amount) {
        //check price.  If the message value is >= to 2 ether then true and continue
        require(msg.value >= _amount, "Not enought Ether provided");
        _;
    }
    //when the room is booked and the payment is sent to the contract the payment is sent to the owner of the contract
    //emit sends an event to the owner that the room is Occupied
    //using the receive feature makes the below items to occur
    receive() external payable onlyWhileVacant costs(2 ether) {
        currentStatus = Statuses.Occupied;
        owner.transfer(msg.value);
        emit Occupy(msg.sender, msg.value);
    }
}

Try it in Remix

This code is for learning and entertainment purposes only. The hotel and vending Solidity smart contract code above has not been audited. Use at your own risk. Remember smart contracts are experimental and could contain bugs.

Click here for more information about how to use the Ethereum test network and how to obtain test ETH.

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