[Ethereum] how to send back token after received some eth

contract-deploymentcontract-designcontract-invocation

how to add this functionality into a token contract?
Function : whenever anyone sends any Ethereum to my contract address, any number more than 0 (even an amount like 0.000000001), I would like to send them back 1000 of my tokens, and send eth that can be contracted to a certain address?

Example contract like this : https://etherscan.io/address/0x55732acec59699e28bad93522684e0d241a64a35

thanks

Best Answer

One of the best prototypes of ERC20 token implementation is the OpenZeppelin's ERC20 implementation.

Follow it's guidelines and you'll archive to do it.

Related with your problem, the error that gives the other answer comes from the ERC20 implementation , if You've overridden the transfer() method and set only one parameter, you won't be able to do it.

Another problem is that msg.value is in wei, so as fas as a wei is indivisible, that may be causing errors too.

So doing it fast it'll be something like that:

contract MyToken {
    // ERC20 token implementation
}

contract SomeContract {
    address tokenAddress;
    MyToken token;
    token.approve(this( which is adress of SomeContract), X amount of tokens is able to donate has to be more than 1000 that is what you send)

    // Run this first, to tell the contract the address 
    // of your token smart contract
    function setTokenAddress(address _tokenAddress) public {
        tokenAddress = _tokenAddress;
        token = MyToken(_tokenAddress);
    }

    function GiveMeTokens() public payable {
        if (msg.value > 1) {
            token.transfer(msg.sender, 1000);
        }
    }
}

Use a standard ERC20 implementation and try again your method.

Related Solutions

ERC-20 – How to Exchange Between ERC20 Token and ETH Automatically

You could add a function similar to this, either in a new contract, or by extending the token contract you are using.

A contract implementing this might be:

import "token/BasicToken.sol";
import "ownership/Ownable.sol";  // link to these contracts below

contract ZonoToken is BasicToken { 

    function deposit() payable
    {
        owner.transfer(msg.value); // see Note 2
        uint newTokens = (msg.value * 10) / 1 ether;
        balances[msg.sender] = balances[msg.sender] + newTokens;
    }

    // fallback function
    function() payable { deposit(); }
}

Notes:

The math of "1 ETH for 10 Tokens" depends on how many decimal places your token has. Above, I assumed that the tokens are indivisible (0 decimals), but with decimals places you would need to adjust the math on the line setting newTokens.
Security consideration: we are assuming that owner is not a contract here. This link explains why we may want to use another pattern for sending ether around (e.g. the withdrawal pattern)

Links:

[Ethereum] Loading smart contract x with tokens; sending eth to smart contract x; receiving tokens for that eth

If you try to run the smart contract on this website Crowdsale In this process you have to build the erc20 token in 1st step and then 2nd step crowdsale , transafer some coins to this crowdsale contract.Anyone send the eth to this crowdsale contract will get the tokens.