Basic Wallet Smart Contract in Solidity

This is a simple example of how to implement the basic functionality of a wallet on the Ethereum blockchain using Solidity.

This contract allows users to deposit ether into the wallet and restricts access to withdrawals to the contract owner.

pragma solidity ^0.8.0;

contract Wallet {
    address public owner;

    event Deposit(address indexed sender, uint256 amount);
    event Withdrawal(address indexed recipient, uint256 amount);

    constructor() {
        owner = msg.sender;
    }

    modifier onlyOwner() {
        require(msg.sender == owner, "Only the owner can call this function");
        _;
    }

    function deposit() payable public {
        emit Deposit(msg.sender, msg.value);
    }

    function withdraw(address payable _recipient, uint256 _amount) public onlyOwner {
        require(address(this).balance >= _amount, "Not enough balance in the wallet");
        _recipient.transfer(_amount);
        emit Withdrawal(_recipient, _amount);
    }

    function getBalance() public view returns (uint256) {
        return address(this).balance;
    }
}

Let's break down the code into smaller parts.

pragma solidity ^0.8.0;

This line specifies the version of Solidity programming language used in the contract. The ^ symbol means that the contract is compatible with any version of Solidity greater than or equal to 0.8.0 and less than 0.9.0 (if it is released).

contract Wallet {
    address public owner;

    event Deposit(address indexed sender, uint256 amount);
    event Withdrawal(address indexed recipient, uint256 amount);

    constructor() {
        owner = msg.sender;
    }

This section defines the wallet contract.

The owner variable, which is a public address variable that stores the address of the contract owner.

The Deposit and Withdrawal events, which are triggered whenever ether is deposited or withdrawn from the wallet.

The constructor function, which is called when the contract is created and sets the owner variable to the address of the contract creator (i.e., the person who implemented the contract).

modifier onlyOwner() {
    require(msg.sender == owner, "Only the owner can call this function");
    _;
}

In this section, a modifier named onlyOwner is defined. A modifier is a special type of function that can be used to modify the behavior of other functions.

In this case, the onlyOwner modifier is used to restrict access to some functions (in this case, the withdraw function) to only the owner of the contract.

The modifier uses the require statement to check if msg.sender (i.e., the person calling the function) is equal to the owner variable, and sends an error message if the condition is not met.

function deposit() payable public {
    emit Deposit(msg.sender, msg.value);
}

This section defines the deposit function. This is a public function that anyone can call and allows Ether to be deposited into the wallet. This function is defined as payable, meaning it can receive Ether. The function sends a deposit event with the sender's address (i.e., the person depositing Ether) and the amount of Ether deposited.

function withdraw(address payable _recipient, uint256 _amount) public onlyOwner {
    require(address(this).balance >= _amount, "Not enough balance in the wallet");
    _recipient.transfer(_amount);
    emit Withdrawal(_recipient, _amount);
}

This section defines the withdraw function. This function is public and can be called by the contract owner (using the onlyOwner modifier). The function accepts two arguments as inputs: _recipient, which is the address of the account that the Ether will be transferred to, and _amount, which is the amount of Ether that should be transferred.

The function first checks if the contract balance is greater than or equal to the requested Ether amount for withdrawal. If the balance is not sufficient, an error message is displayed.

If the balance is sufficient, the function transfers the requested amount of Ether to the specified recipient address using the transfer function. Then, the function sends a withdrawal event with the recipient's address and the amount of Ether that was withdrawn.

function getBalance() public view returns (uint256) {
    return address(this).balance;
}

In this section, the getBalance function is defined. This is a public function that anyone can call and it will return the current balance of the contract (i.e., the amount of ether held in the wallet).

Overall, this contract allows anyone to deposit ether into the wallet, but only the contract owner can withdraw ether from the wallet. The contract also provides a function to check the current balance of the wallet. This basic functionality can be expanded upon in the future for more complex and customized use cases.