How append an object to a bytes array?

Question

I have a function which staticcalls a function which returns 3 different variables (uint112 reserve0, uint112 reserve1, uint32 blockTimestampLast).

(bool success, bytes memory result) = contractAddr.staticcall(signatureID);

After the call, I would like to add the contractAddr variable (which has an address type) to the result byte array.

Based on the questions I found, I tried to use the following lines to add the address:

result[3] = abi.encodePacked(contractAddr);

And then got this error:

TypeError: Type bytes memory is not implicitly convertible to expected type bytes1.

I know this is because result is memory and it can't be altered. To fix this I tried to create a new bytes[] but got the TypeError: Type bytes1 is not implicitly convertible to expected type bytes memory. error when I tried the following:

  (bool success, bytes memory result) = contractAddr.staticcall(signatureID);
  bytes[] memory resultsCurrent = new bytes[](4);
  resultsCurrent[0] = result[0];
  resultsCurrent[1] = result[1];
  resultsCurrent[2] = result[2];
  resultsCurrent[3] = abi.encodePacked(contractAddr);

My question is, how could I create a bytes type variable which holds the three object of result at the index of 0,1,2 and abi.encodePacked(contractAddr) at the index of 3? My goal is to compose a view function from it to avoid paying gas fee for the calls.

Answer 1

The problem here is, the returned result from staticcall is not of a type bytes array, but bytes. So your function will not work as intended anyhow. Depending on what you want to achieve you have a few options.

1. Encode address with result, where rez is of type bytes: rez = abi.encodePacked(result, contractAddr);

2. Create bytes array and pass result as first element and address as second

bytes[] memory resultsCurrent= new bytes[](2); 
resultsCurrent[0] = result; 
resultsCurrent[1] = abi.encodePacked(contractAddr);