Permissions: Add Allowances for External Roles

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In this step we are adding a mapping so we can store address => uint amounts. This will be like an array that stores [0x123546…] an address, to a specific number. So, we always know how much someone can withdraw. We also add a new modifier that checks: Is it the owner itself or just someone with allowance?


//SPDX-License-Identifier: MIT
 
pragma solidity 0.8.1;
 
import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/access/Ownable.sol";
 
contract SharedWallet is Ownable {
    function isOwner() internal view returns(bool) {
        return owner() == msg.sender;
    }
 
    mapping(address => uint) public allowance;
    
    function addAllowance(address _who, uint _amount) public onlyOwner {
        allowance[_who] = _amount;
    }
    
    modifier ownerOrAllowed(uint _amount) {
        require(isOwner() || allowance[msg.sender] >= _amount, "You are not allowed!");
        _;
    }
    
    function withdrawMoney(address payable _to, uint _amount) public ownerOrAllowed(_amount) {
        require(_amount <= address(this).balance, "Contract doesn't own enough money");
        _to.transfer(_amount);
    }
    
    receive() external payable {
        
    }
}

Did you catch the bug?

Have a look at the withdrawMoney functionality and think it through!

In the next lecture we’re going to improve our smart contract a little bit and avoid double spending.