Check if a Solidity contract function is running as part of a constuctor

contracthelper.sol

/*
 * This is a helper to check if a Solidity contract function is running as part of a constructor.
 */
library ContractHelper {
    function runningInConstructor() internal view returns (bool ret) {
        assembly {
            ret := iszero(iszero(extcodesize(address)))
        }
    }
}