Try to transfer funds if they're available in solidity

Question

I'd like to try to refund a call. However:

1. If my contract doesn't have enough native tokens
2. The sender is not payable, I don't want to fail.

I've tried it in the following way:

function performLoop() nonReentrant external {
    (bool canExecute, ) = requiresExecution(false);
    require(canExecute, "PEL: Nothing to Execute");
    uint gasAtStart = gasleft();


    uint256 gasSpent = gasAtStart - gasleft() + 28925;
    try payable(msg.sender).transfer((gasSpent * tx.gasprice) + (gasSpent * (tx.gasprice/10))) { } catch { }
}

However I cannot use a try catch here since:

Try can only be used with external function calls and contract creation calls.

How can I try to send fund if they're available

Answer 1

You can use call instead of transfer. call doesn't automatically revert on failure, but returns a boolean with the status of the call. So can just you ignore this value.

(bool success, ) = payable(msg.sender).call{value: gasSpent*tx.gasprice + gasSpent*(tx.gasprice/10)}();
// require(success);  // keep this commented to never revert on failure

Answer 2

You can not use try catch to send funds. try catch can only be used for external contract call.

Instead you can use if statement

if(address(this).balance > 0){
   (bool success, ) = msg.sender.call{value: address(this).balance}("");
   require(success, "not able to refund");
}