Why not make a new memory variable to save the storage variable and compare the two memory variable?

[flyq]

https://forum.ethereum.org/discussion/3238/string-compare-in-solidity

[flyq]

AjoyBhatia's post

[flyq]

    function registerByAdmin(address _user, string _ipfsAddr)
        public
        onlyAdmins
        whenNotPaused
    {
        require(isOnAdmin == true);
        require(indexOfIpfs[_ipfsAddr] == 0 && keccak256(abi.encodePacked(ipfsAddrOf[0])) != keccak256(abi.encodePacked(_ipfsAddr)));
        uint256 _tokenId = allTokens.length;
        require(!exists(_tokenId));

        _mint(_user, _tokenId);
        ipfsAddrOf[_tokenId] = _ipfsAddr;
        indexOfIpfs[_ipfsAddr] = _tokenId;
    }

ipfsAddrOf[0] is a storage, ipfsAddr is memory. and code above is ok