Smartcontract for Bico token sales
Go to https://www.ethereum.org/ and download the Ethereum Wallet for your OS. When it starts switch to the Test Network if you want to play around with contract creation
Go to Contracts -> Deploy New Contract and add the following source code:
/* Smart contract for your ico */ pragma solidity ^0.4.13;
contract tokenRecipient { function receiveApproval(address _from, uint256 _value, address _token, bytes _extraData); }
contract MyToken { /* Public variables of the token */ string public name; string public symbol; uint8 public decimals; uint256 public totalSupply;
/* This creates an array with all balances */
mapping (address => uint256) public balanceOf;
mapping (address => mapping (address => uint256)) public allowance;
/* This generates a public event on the blockchain that will notify clients */
event Transfer(address indexed from, address indexed to, uint256 value);
/* This notifies clients about the amount burnt */
event Burn(address indexed from, uint256 value);
/* Initializes contract with initial supply tokens to the creator of the contract */
function MyToken(
uint256 initialSupply,
string tokenName,
uint8 decimalUnits,
string tokenSymbol
) {
balanceOf[msg.sender] = initialSupply; // Give the creator all initial tokens
totalSupply = initialSupply; // Update total supply
name = tokenName; // Set the name for display purposes
symbol = tokenSymbol; // Set the symbol for display purposes
decimals = decimalUnits; // Amount of decimals for display purposes
}
/* Internal transfer, only can be called by this contract */
function _transfer(address _from, address _to, uint _value) internal {
require (_to != 0x0); // Prevent transfer to 0x0 address. Use burn() instead
require (balanceOf[_from] > _value); // Check if the sender has enough
require (balanceOf[_to] + _value > balanceOf[_to]); // Check for overflows
balanceOf[_from] -= _value; // Subtract from the sender
balanceOf[_to] += _value; // Add the same to the recipient
Transfer(_from, _to, _value);
}
/// @notice Send `_value` tokens to `_to` from your account
/// @param _to The address of the recipient
/// @param _value the amount to send
function transfer(address _to, uint256 _value) {
_transfer(msg.sender, _to, _value);
}
/// @notice Send `_value` tokens to `_to` in behalf of `_from`
/// @param _from The address of the sender
/// @param _to The address of the recipient
/// @param _value the amount to send
function transferFrom(address _from, address _to, uint256 _value) returns (bool success) {
require (_value < allowance[_from][msg.sender]); // Check allowance
allowance[_from][msg.sender] -= _value;
_transfer(_from, _to, _value);
return true;
}
/// @notice Allows `_spender` to spend no more than `_value` tokens in your behalf
/// @param _spender The address authorized to spend
/// @param _value the max amount they can spend
function approve(address _spender, uint256 _value)
returns (bool success) {
allowance[msg.sender][_spender] = _value;
return true;
}
/// @notice Allows `_spender` to spend no more than `_value` tokens in your behalf, and then ping the contract about it
/// @param _spender The address authorized to spend
/// @param _value the max amount they can spend
/// @param _extraData some extra information to send to the approved contract
function approveAndCall(address _spender, uint256 _value, bytes _extraData)
returns (bool success) {
tokenRecipient spender = tokenRecipient(_spender);
if (approve(_spender, _value)) {
spender.receiveApproval(msg.sender, _value, this, _extraData);
return true;
}
}
/// @notice Remove `_value` tokens from the system irreversibly
/// @param _value the amount of money to burn
function burn(uint256 _value) returns (bool success) {
require (balanceOf[msg.sender] > _value); // Check if the sender has enough
balanceOf[msg.sender] -= _value; // Subtract from the sender
totalSupply -= _value; // Updates totalSupply
Burn(msg.sender, _value);
return true;
}
function burnFrom(address _from, uint256 _value) returns (bool success) {
require(balanceOf[_from] >= _value); // Check if the targeted balance is enough
require(_value <= allowance[_from][msg.sender]); // Check allowance
balanceOf[_from] -= _value; // Subtract from the targeted balance
allowance[_from][msg.sender] -= _value; // Subtract from the sender's allowance
totalSupply -= _value; // Update totalSupply
Burn(_from, _value);
return true;
}
}
After it compiles you can add your desired parameters:
- In pick contract select "My Token"
- Initially supply put the total number of tokens that will exist (e.x. 100)
- Choose the name of your token (e.x. BICO)
- Select a decimal value for your token, if you want it to be exchanged in 0.5 parts etc.
- Put the Token symbol you want for your token
Deploy your contract by putting your password (Remember to have enough ether for the gas fees) Save the address of the token as you will use it in the next step
For the croudsale we will use similar steps. Go to Contracts - > Deploy contract and paste the following code.
/* Smart contract for your croudsale */ pragma solidity ^0.4.2; contract token { function transfer(address receiver, uint amount); }
contract Crowdsale { address public beneficiary; uint public fundingGoal; uint public amountRaised; uint public deadline; uint public price; token public tokenReward; mapping(address => uint256) public balanceOf; bool fundingGoalReached = false; event GoalReached(address beneficiary, uint amountRaised); event FundTransfer(address backer, uint amount, bool isContribution); bool crowdsaleClosed = false;
/* data structure to hold information about campaign contributors */
/* at initialization, setup the owner */
function Crowdsale(
address ifSuccessfulSendTo,
uint fundingGoalInEthers,
uint durationInMinutes,
uint etherCostOfEachToken,
token addressOfTokenUsedAsReward
) {
beneficiary = ifSuccessfulSendTo;
fundingGoal = fundingGoalInEthers * 1 ether;
deadline = now + durationInMinutes * 1 minutes;
price = etherCostOfEachToken * 1 ether;
tokenReward = token(addressOfTokenUsedAsReward);
}
/* The function without name is the default function that is called whenever anyone sends funds to a contract */
function () payable {
require (!crowdsaleClosed);
uint amount = msg.value;
balanceOf[msg.sender] += amount;
amountRaised += amount;
tokenReward.transfer(msg.sender, amount / price);
FundTransfer(msg.sender, amount, true);
}
modifier afterDeadline() { if (now >= deadline) _; }
/* checks if the goal or time limit has been reached and ends the campaign */
function checkGoalReached() afterDeadline {
if (amountRaised >= fundingGoal){
fundingGoalReached = true;
GoalReached(beneficiary, amountRaised);
}
crowdsaleClosed = true;
}
function safeWithdrawal() afterDeadline {
if (!fundingGoalReached) {
uint amount = balanceOf[msg.sender];
balanceOf[msg.sender] = 0;
if (amount > 0) {
if (msg.sender.send(amount)) {
FundTransfer(msg.sender, amount, false);
} else {
balanceOf[msg.sender] = amount;
}
}
}
if (fundingGoalReached && beneficiary == msg.sender) {
if (beneficiary.send(amountRaised)) {
FundTransfer(beneficiary, amountRaised, false);
} else {
//If we fail to send the funds to beneficiary, unlock funders balance
fundingGoalReached = false;
}
}
}
}
After it compiles you can add your desired parameters:
- Select CroudSale for the contract type
- In "If successful send to address" put your main account address
- Put the funding goal which is the maximum ethereum your tokens will add up to (Keep in mind to only distribute half the token amount so no single entity controlls more than 51%) (e.x 250)
- Duration in minutes is the total duration of the crowdsale phase - 45,000 (31 days)
- Then put the ether cost of each token (e.x. 5)
- Finally put the address of the token as the reward (created in the previous step)
- Deploy the contract like you did in the previous step.
Important!!!! With 100 tokens in the previous step we want to sell only 50% so 50 tokens. Since we put 5 ether per token our goal is to reach 250 ether.
- Click the address of the crowdsale, then deposit and send 50 tokens to the crowdsale.