[Ethereum] Data location must be “calldata” for parameter in external function, but none was given

remixsolidity

I'm trying to compile my code in Remix and I try to fix it but I keep getting the same error:

Data location must be “calldata” for parameter in external function, but none was given".

The problem is in the function createNewUser() external

event startMessage(string message);

function createNewUser (string _name, string _email, uint _aadhaar, string _sign) external {
  if((checkUser[msg.sender] == true)||(checkAadhaar[_aadhaar] == true))
  {
    startMessage('Failed !! User already Registered..');
  }
  else if((checkUser[msg.sender] != true)&&(checkAadhaar[_aadhaar] != true))
  {
    var newUser = Person(msg.sender, _name, _email, _aadhaar, _sign, new uint[](0), new uint[](0));
    addressToPerson[msg.sender] = newUser;

    checkUser[msg.sender] = true;
    checkAadhaar[_aadhaar] = true;

    startMessage('Welcome !! Successful Registration on Charter');
  }
}

Best Answer

Either

function createNewUser (string memory _name, string memory _email, uint _aadhaar, string memory _sign) public

function createNewUser (string calldata _name, string calldata _email, uint _aadhaar, string calldata _sign) external

Explanation:

Unlike tradition computers, EVM has many different “memories”, each accessed with its own set of instructions. Thus one cannot have “universal” memory pointer, but has to use different pointer types for different “memories”.

In Solidity, all reference types, such as string, bytes, or struct, should always be accompanied with explicit specifier telling the compiler what “memory” the reference actually refers to. See Reference Types section in documentation for details.

While, basically, “external” is just syntactic sugar for “public“, for some reason Solidity compiler disallows “memory” references in “external“ function parameters. The documentation just says:

Note that external functions require parameters with a data location of calldata.

without any further explanation. The compiler also disallows “calldata” references in parameters of non-“external” functions, and there is good reason for this, because non-“external” functions may be called internally, thus there could be no call data at all.

Related Solutions

[Ethereum] TypeError: Data location must be “memory” for parameter in function, but none was given

From this:

pragma solidity^0.5.0;

contract Contract {
    string public name;

    function Contracts(string passedName) public {
        name = passedName;
    }

    function setName(string newName) public {
        name = newName;

    }

}

To This:

pragma solidity^0.5.0;

contract Contract {
    string public name;

    function Contracts(string memory passedName) public {
        name = passedName;
    }

    function setName(string memory newName) public {
        name = newName;

    }

}

Make sure to use "" to wrap text. Using '' will give you:

transact to Contract.Contracts errored: Error encoding arguments: SyntaxError: JSON.parse: unexpected character at line 1 column 2 of the JSON data

[Ethereum] TypeError: Data location must be “storage” or “memory” for parameter in function, but none was given

As of Solidity 0.5.0. https://solidity.readthedocs.io/en/v0.5.0/050-breaking-changes.html

Explicit data location for all variables of struct, array or mapping types is now mandatory. This is also applied to function parameters and return variables. For example, change uint[] x = m_x to uint[] storage x = m_x, and function f(uint[][] x) to function f(uint[][] memory x) where memory is the data location and might be replaced by storage or calldata accordingly. Note that external functions require parameters with a data location of calldata.

You can fix it by saying memory for the bytes argument which is an array of byte.

pragma solidity 0.5.0;

contract Memory {
    function addTransaction(address destination, uint value, bytes memory data)
        internal
        returns (uint transactionId)
    {
        return 0;
    }
}

Warnings are safe to ignore. I wanted to keep this example as close as possible to the original and confirm it compiles.

Best Answer

Related Solutions

[Ethereum] TypeError: Data location must be “memory” for parameter in function, but none was given

[Ethereum] TypeError: Data location must be “storage” or “memory” for parameter in function, but none was given

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