Custom Searcher Contract

Searchers can use their in-house custom contracts to execute the opportunities Express Relay provides. In this case, they must construct the bids based on the opportunity details.

Refer to the following example of a custom contract that executes liquidation transactions:

...
function callLiquidation(Opportunity memory opp){
    for (uint i=0; i<opp.sell_tokens.length; i++) {
        let token = opp.sell_tokens[i];
        IERC20(token.contract).approve(opp.contract, token.amount);
    }
 
    uint256[] before = new uint256[](opp.buy_tokens.length);
    for (uint j=0; j<opp.buy_tokens.length; j++) {
        let token = opp.buy_tokens[j];
        before = IERC20(token.contract).balanceOf(address(this));
    }
 
    opp.target_contract.call{value: opp.target_call_value}(opp.target_calldata);
 
    uint256[] after = new uint256[](opp.buy_tokens.length);
    for (uint j=0; j<opp.buy_tokens.length; j++) {
        let token = opp.buy_tokens[j];
        after = IERC20(token.target_contract).balanceOf(address(this));
 
        assert(after[j] == before[j] + token.amount);
    }
}
...

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Make sure to allow the Express Relay contract to call the relevant methods in your custom contract.

Last updated on March 4, 2025