How can I architecture following in the most optimal way;
I'm trying to have a flow between contract A, B, and C.
Contract C should be sending ERC20 to contract B.
Contract A should be sending Ether to contract B.
Contract B should accept the two values from contract C & A, and perform a swap between the two only if both contract C & A gives their consent to contract B to execute the swap of their sent values to contract B.
So in this specific scenario, we are dealing with a two-phase process.
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1 Answer
Contract B should accept the two values from contract C & B, and perform a swap between the two only if both contract C & B gives their consent to contract B
Do you mean two values from C & A and only if C & A give their consent, not C & B?
Assuming that's what you meant, I'd do something like this.
contract B {
// this mapping will store if address A has given permission for the
// contract to swap with address C.
mapping (address => (address => bool)) permissionGiven;
mapping (address => uint) ethBalance; //ether balance
mapping (address => uint) balances; //ERC20 token balance
function () payable {
ethBalance[msg.sender] = ethBalance[msg.sender].add(msg.value);
}
function givePermission (address _a) public {
permissionGiven[msg.sender][a] = true;
}
function swap(address _a, address _c) public {
if (permissionGiven[_c][_a] && permissionGiven[_a][_c]) {
_c.transfer(ethBalance[_a]);
transfer(_a, balances[_c]);
}
}
function transfer (address _to, uint _tokens) {
// usual ERC20 transfer function
}
}
In this implementation, contracts C and A can call givePermission, passing in the addresses of A and C respectively. Then, after depositing ether/ tokens and calling swap, the ether will be transferred to C and the tokens to A.
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Yes, you're right Elizabeth, I'll correct the description, that's what I meant. However, both contract A & C should give permission before a swap is initiated.– NowsyMeCommented May 5, 2018 at 1:15
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I changed the swap function if statement to reflect that. The way I had it before was assuming A had already given permission, and C had to call swap to check if A has given permission; if A had, then it would commence with the swap.– nootCommented May 5, 2018 at 1:22
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I see. they should, however, give permission to contract B and not each other.– NowsyMeCommented May 5, 2018 at 11:07