Basic Mapping Question

Question

Very basic question but would appreciate any help understanding this. I don't quite understand the logic behind the += operator within the below mapping. Please see below code

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

    function sendMoney() public payable {
        balanceReceived[msg.sender] += msg.value;
    }

How can you logically add and assign and have - balanceReceived [msg.sender] = balanceReceived [msg.sender] + msg.value?

I am sure I am looking at this the wrong way but the balanceRecieved [msg.sender] is a address so how can you add that to a uint value of msg.value?

Answer 1

without seeing the mapping definition I'd guess it's something like

mapping(address => uint) balanceReceived;

that means balanceReceived[msg.sender] is not an address, it's what an address is mapped to, which is a uint

Answer 2

balanceReceived should be of type mapping(address => uint), and msg.sender is of type address, msg.value is of type uint.

So balanceReceived[msg.sender] is a uint value but not an address.

Does that make sense?