These are chat archives for ethereum/tutorials

25th
Jul 2018
Michael Rice
@mrice
Jul 25 2018 02:34
@cryptoempire - are you looking for both the front end and back end? If you just want to help out with some solidity code I’ve got a repo I could use some eyes on
cryptoempire
@cryptoempire
Jul 25 2018 03:44
@mrice both, I just want to further work on and improve my dapp skills
Michael Rice
@mrice
Jul 25 2018 05:17
@cryptoempire - cool - just hit you up on private channel
daraohara
@daraohara
Jul 25 2018 14:40
Is the 'full coin code' on /token still acceptable? are there any security issues? i'm using a chunk in a charity project.
Michael Rice
@mrice
Jul 25 2018 15:09
@daraohara - that’s an interesting question. are you talking about https://www.ethereum.org/token?
carlosrobles89
@carlosrobles89
Jul 25 2018 19:59
Hello, I have two very basic questions:
1) What code language is shown in the Ethereum examples?
2) Does one need to be fully proficient at coding to use the blockchain or just enough to be dangerous?
oglebd
@oglebd
Jul 25 2018 23:40
is there a token and crowdsale code available?
TarrahArshad
@TarrahArshad
Jul 25 2018 23:40
@oglebd what u like ?
@carlosrobles89 code is on javascript solidity
oglebd
@oglebd
Jul 25 2018 23:41
i copied and pasted the code on eth website and i get error messages
just for the token creation
TarrahArshad
@TarrahArshad
Jul 25 2018 23:41
@oglebd what is ur error ?
oglebd
@oglebd
Jul 25 2018 23:41

Could not compile source code.

Expected pragma, import directive or contract/interface/library definition.
event Transfer(address indexed from, address indexed to, uint256 value);
^---^

is the eth website not up to date?
TarrahArshad
@TarrahArshad
Jul 25 2018 23:42
@oglebd share u code
oglebd
@oglebd
Jul 25 2018 23:42
// This generates a public event on the blockchain that will notify clients
event Transfer(address indexed from, address indexed to, uint256 value);

// This generates a public event on the blockchain that will notify clients
event Approval(address indexed _owner, address indexed _spender, uint256 _value);

// This notifies clients about the amount burnt
event Burn(address indexed from, uint256 value);

/**
 * Constructor function
 *
 * Initializes contract with initial supply tokens to the creator of the contract
 */
function TokenERC20(
    uint256 initialSupply,
    string tokenName,
    string tokenSymbol
) public {
    totalSupply = initialSupply * 10 ** uint256(decimals);  // Update total supply with the decimal amount
    balanceOf[msg.sender] = totalSupply;                // Give the creator all initial tokens
    name = tokenName;                                   // Set the name for display purposes
    symbol = tokenSymbol;                               // Set the symbol for display purposes
}

/**
 * Internal transfer, only can be called by this contract
 */
function _transfer(address _from, address _to, uint _value) internal {
    // Prevent transfer to 0x0 address. Use burn() instead
    require(_to != 0x0);
    // Check if the sender has enough
    require(balanceOf[_from] >= _value);
    // Check for overflows
    require(balanceOf[_to] + _value >= balanceOf[_to]);
    // Save this for an assertion in the future
    uint previousBalances = balanceOf[_from] + balanceOf[_to];
    // Subtract from the sender
    balanceOf[_from] -= _value;
    // Add the same to the recipient
    balanceOf[_to] += _value;
    emit Transfer(_from, _to, _value);
    // Asserts are used to use static analysis to find bugs in your code. They should never fail
    assert(balanceOf[_from] + balanceOf[_to] == previousBalances);
}

/**
 * Transfer tokens
 *
 * 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) public returns (bool success) {
    _transfer(msg.sender, _to, _value);
    return true;
}

/**
 * Transfer tokens from other address
 *
 * Send `_value` tokens to `_to` on 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) public returns (bool success) {
    require(_value <= allowance[_from][msg.sender]);     // Check allowance
    allowance[_from][msg.sender] -= _value;
    _transfer(_from, _to, _value);
    return true;
}

/**
 * Set allowance for other address
 *
 * Allows `_spender` to spend no more than `_value` tokens on your behalf
 *
 * @param _spender The address authorized to spend
 * @param _value the max amount they can spend
 */
function approve(address _spender, uint256 _value) public
    returns (bool success) {
    allowance[msg.sender][_spender] = _value;
    emit Approval(msg.sender, _spender, _value);
    return true;
}

/**
 * Set allowance for other address and notify
 *
 * Allows `_spender` to spend no more than `_value` tokens on 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)
    public
    returns (bool success) {
    tokenRecipient spender = tokenRecipient(_spender);
    if (approve(_spender, _value)) {
        spender.receiveApproval(msg.sender, _value, this, _extraData);
wait one sec
not all there

pragma solidity ^0.4.16;

interface tokenRecipient { function receiveApproval(address _from, uint256 _value, address _token, bytes _extraData) external; }

contract TokenERC20 {
// Public variables of the token
string public name;
string public symbol;
uint8 public decimals = 18;
// 18 decimals is the strongly suggested default, avoid changing it
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 generates a public event on the blockchain that will notify clients
event Approval(address indexed _owner, address indexed _spender, uint256 _value);

// This notifies clients about the amount burnt
event Burn(address indexed from, uint256 value);

/**
 * Constructor function
 *
 * Initializes contract with initial supply tokens to the creator of the contract
 */
function TokenERC20(
    uint256 initialSupply,
    string tokenName,
    string tokenSymbol
) public {
    totalSupply = initialSupply * 10 ** uint256(decimals);  // Update total supply with the decimal amount
    balanceOf[msg.sender] = totalSupply;                // Give the creator all initial tokens
    name = tokenName;                                   // Set the name for display purposes
    symbol = tokenSymbol;                               // Set the symbol for display purposes
}

/**
 * Internal transfer, only can be called by this contract
 */
function _transfer(address _from, address _to, uint _value) internal {
    // Prevent transfer to 0x0 address. Use burn() instead
    require(_to != 0x0);
    // Check if the sender has enough
    require(balanceOf[_from] >= _value);
    // Check for overflows
    require(balanceOf[_to] + _value >= balanceOf[_to]);
    // Save this for an assertion in the future
    uint previousBalances = balanceOf[_from] + balanceOf[_to];
    // Subtract from the sender
    balanceOf[_from] -= _value;
    // Add the same to the recipient
    balanceOf[_to] += _value;
    emit Transfer(_from, _to, _value);
    // Asserts are used to use static analysis to find bugs in your code. They should never fail
    assert(balanceOf[_from] + balanceOf[_to] == previousBalances);
}

/**
 * Transfer tokens
 *
 * 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) public returns (bool success) {
    _transfer(msg.sender, _to, _value);
    return true;
}

/**
 * Transfer tokens from other address
 *
 * Send `_value` tokens to `_to` on 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) public returns (bool success) {
    require(_value <= allowance[_from][msg.sender]);     // Check allowance
    allowance[_from][msg.sender] -= _value;
    _transfer(_from, _to, _value);
    return true;
}

/**
 * Set allowance for other address
 *
 * Allows `_spender` to spend no more than `_value` tokens on your behalf
 *
 * @param _spender The address authorized to spend
 * @param _value the max amount they can spend
 */
function approve(address _spender, uint256 _value) public
    returns (bool success) {
    allowance[msg.sender][_spender] = _value;
    emit Approval(msg.sender, _spender, _value);
    return true;
}

/**
 * Set allowance for other address and notify
 *
 * Allows `_spender` to spend no more than `_
TarrahArshad
@TarrahArshad
Jul 25 2018 23:43
@oglebd give me access anydesk or tv I solve ur problem
oglebd
@oglebd
Jul 25 2018 23:45
not sure what you mean
TarrahArshad
@TarrahArshad
Jul 25 2018 23:47
@oglebd ur code is not complete
oglebd
@oglebd
Jul 25 2018 23:47
ah ok
i just copied it from the ethereum website
TarrahArshad
@TarrahArshad
Jul 25 2018 23:47
whick link ?
using it in ethererum wallet
TarrahArshad
@TarrahArshad
Jul 25 2018 23:48
where u compile ?
oglebd
@oglebd
Jul 25 2018 23:48
ethererum wallet, solidarity contract source code
TarrahArshad
@TarrahArshad
Jul 25 2018 23:49
@oglebd add my skype id = tarraharshad
show ur desktop
I teach u solve it
oglebd
@oglebd
Jul 25 2018 23:58
ah shoot my skype aint working
anyways, stuck on
function TokenERC20(
it's waiting for something
am i supposed to put like an emit there in the code?