[Ethereum] Solidity Help – Undeclared Identifier – onlyOwner WithdrawEther


I'm new to Solidity and attempting to add a withdraw ether function for my contract which enables me to release funds the parent contract account, but the compiler (remix) keeps on giving me an undeclared identifier error: onlyOwner is an undeclared identifier.

Any help? Do I have to define, and if so, how?

Please and thanks for the help!

Here's my code: (Concensys Template)

pragma solidity ^0.4.18;import "./EIP20Interface.sol";               
contract BLUBLOXX is EIP20Interface {

uint256 constant private MAX_UINT256 = 2**256 - 1;
mapping (address => uint256) public balances;
mapping (address => mapping (address => uint256)) public allowed;
The following variables are OPTIONAL vanities. One does not have to include them.
They allow one to customise the token contract & in no way influences the core functionality.
Some wallets/interfaces might not even bother to look at this information.
string public name;                   //fancy name: eg Simon Bucks
uint8 public decimals;                //How many decimals to show.
string public symbol;                 //An identifier: eg SBX

uint price = 0.001 ether;

function BLUBLOXX(
    uint256 _initialAmount,
    string _tokenName,
    uint8 _decimalUnits,
    string _tokenSymbol
) public {
    balances[msg.sender] = _initialAmount;               // Give the creator all initial tokens
    totalSupply = _initialAmount;                        // Update total supply
    name = _tokenName;                                   // Set the name for display purposes
    decimals = _decimalUnits;                            // Amount of decimals for display purposes
    symbol = _tokenSymbol;                               // Set the symbol for display purposes

function transfer(address _to, uint256 _value) public returns (bool success) {
    require(balances[msg.sender] >= _value);
    balances[msg.sender] -= _value;
    balances[_to] += _value;
    Transfer(msg.sender, _to, _value);
    return true;

function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
    uint256 allowance = allowed[_from][msg.sender];
    require(balances[_from] >= _value && allowance >= _value);
    balances[_to] += _value;
    balances[_from] -= _value;
    if (allowance < MAX_UINT256) {
        allowed[_from][msg.sender] -= _value;
    Transfer(_from, _to, _value);
    return true;

function balanceOf(address _owner) public view returns (uint256 balance) {
    return balances[_owner];

function approve(address _spender, uint256 _value) public returns (bool success) {
    allowed[msg.sender][_spender] = _value;
    Approval(msg.sender, _spender, _value);
    return true;

function allowance(address _owner, address _spender) public view returns (uint256 remaining) {
    return allowed[_owner][_spender];

function() public payable{

    uint toMint = msg.value/price;
    totalSupply += toMint;

    Transfer(0, msg.sender, toMint);


function withdrawEther() external onlyOwner {

Best Answer

Yes, you must define the modifier within your contract. Assuming by owner you mean the contract creator, you must define a variable in your contract.

address private owner;

and in the constructor make sure you set it to the contract creator

owner = msg.sender;

then to create the modifier, this would probably do the trick.

modifier onlyOwner(){
    require(msg.sender == owner);
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