Sending ether from one contract to another

Question

I have a function makePayment in one Contract:

function payLoan(Loan _loanAddress) payable onlyOwner public {

// Outgoing payment
Loan myLoan = Loan(_loanAddress);
uint256 payment = msg.value;

// Make payment if sufficient funds, otherwise only pay what is available
if (funds >= payment){

    // Make payment
    myLoan.makePayment.value(payment);
    funds -= payment;
}else{

    // Partial payment
    myLoan.makePayment.value(funds);
    funds = 0;
}

and I want to make a payment into another contract with the function makePayment:

    function makePayment() onlyOwner payable public {

        received = msg.value;
        if (received >= balance){
            received    -= balance;
            amtPaid     += balance;
            balance     = 0;
        } else {
            balance     -= received;
            amtPaid     += received;
            received    = 0;
        }

    }

It seems to work and the funds are received by the first contract, but the amount sent is never received. None of the variables are changed as a result of the call. Any idea what is wrong? Thanks.

Here is a further simplification and revised attempt. I still get the error "transact to Borrower.payLoan errored: VM error: revert. revert The transaction has been reverted to the initial state. Note: The constructor should be payable if you send value. Debug the transaction to get more information."

    pragma solidity ^0.4.18;

contract Borrower {
    uint256 public amountReceived;

    function Borrower() payable public {
    }

    function payLoan(Loan _loan) payable public {

        // Outgoing payment
        Loan loan = Loan(_loan);
        amountReceived = msg.value;

        // Make payment
        loan.payLoan.value(amountReceived)();
    }   

    function getThisBalance() public view returns (uint256){

        return this.balance;
    }
} // Borrower

contract Loan {
    address public borrower;
    uint256 public loanBalance;

    function payLoan() payable public {
        uint256 received = msg.value;
        loanBalance -= received;
        }

    function Loan(address _borrower) payable public {
        borrower    = _borrower;
        loanBalance = msg.value;
        }

    function getThisBalance() public view returns (uint256){

        return this.balance;
    }
} // Loan

Answer 1

I think you're missing parentheses to actually call the function:

myLoan.makePayment.value(payment)();

and

myLoan.makePayment.value(funds)();

Answer 2

So I have figured it out. The problem was that when I was running payLoan I entered the borrower address into the box to the left of create circled in red instead of the box circled in yellow to the right of the function payLoan. I did not notice that I could click there and enter the address.

Now that I can get the function to fire properly, I cleaned up the code as well. I also realized that I did not need to fund Borrower as any payments were coming from msg.sender anyway. I also made the loanBalance itself a counter not holding ether but rather tracking the payments actually made. Now when I send ether, loanBalance goes down by the amount of ether received and Loan has a balance corresponding to the amount of ether received. Simple program but very educational! Here is the code:

pragma solidity ^0.4.18;

contract Borrower {
    string  public borrowerName;
    uint256 public amountToPay;

    function payLoan(Loan _loan) payable public {

        // Outgoing payment
        Loan loan   = Loan(_loan);
        amountToPay = msg.value;

        // Make payment
        loan.makePayment.value(amountToPay)();
    }   

    function getThisBalance() public view returns (uint256){

        return this.balance;
    }
} // Borrower

contract Loan {

        address public borrower;
        uint256 public loanBalance;

        uint256 public received;

        function Loan(address _borrower, uint _loanBalance) public {
            borrower    = _borrower;
            loanBalance = _loanBalance;
            }

        function makePayment() payable public {

            received    =  msg.value;
            loanBalance -= received;
        }

    function getThisBalance() public view returns (uint256){

        return this.balance;
    }
} // Loan