Example showing how to use DELEGATECALL

using-delegatecall-safely.sol

// Author: Nick Mudge (https://twitter.com/mudgen)
// This is part of my tweet thread, "Six things you need to know to use DELEGATECALL safely": https://twitter.com/mudgen

// Shows how to use DELEGATECALL

// Using OpenZeppelin's Address library check to see if 
// myContract has code.
require(Address.isContract(myContractAddress), "Address has no code");
// Set function argument we are going to use.
uint myArg = 10;
// Create the function call with argument.
bytes memory functionCall = abi.encodeWithSignature("myFunction(uint256)", myArg);
// Execute delegatecall
(
    bool success, 
    bytes memory result
) = myContractAddress.delegatecall(functionCall);

// If the function call succeeded
if(success) {
    // We know that "myFunction" returns an
    // uint256 so we decode it and return it.
    return abi.decode(result, (uint256));
}
else {
    // If function did not succeed then revert with
    // error message if there is one.
    if (result.length > 0) {
        // bubble up the error
        revert(string(result));
    } else {
        revert("myFunction had an error");
    }
}