solidity – Crowdsale with Existing Token

contract-designcontract-developmentsolidity

This might be a very general question, though I'd like if someone could clarify on how to within a crowdsale contract use an already deployed token contract with a fixed supply. I know how to create a mintable token internally from the crowdsale contract but I've never played around with an existing token though. Thank you

Best Answer

On your crowd sale contract, import the ERC20 interface and then code your smart contract to allow an ERC20 token to be set.

function setToken(address tokenAddress) {
        require(msg.sender == _ownerAddress);        
        _myToken = ERC20(tokenAddress);
    }

Now your crowd sale contract can call _myToken.balanceOf(this); to get the number of tokens it owns, and _mytoken.transfer(address, count); to distribute tokens according to whatever your desired crowdsale logic is.

So now all you need to do is transfer some or all of your minted tokens to the crowdsale contract address and you're ready to go.

Related Solutions

Solidity – Boolean Returning Method: Validate Input with “if” or require()

I'd like to introduce a supply limit and am unsure how to validate the input correctly. Should I use require(), throw, or is it preferred to return a boolean as the caller might expect

Its pretty straight forward that the method returns bool and I would suggest to use if and return bool(state is defined either true or false)

with respect to require/ throw it would return "Invalid Opcode" and also it utilizes equal gas as above and would return undefined sate (Invalid Opcode/ not much user friendly) which is not preferred. Moreoften require is used when you change state of variable which is not the case here.

Contract Development – How to Automatically Transfer Ether in Token Contract

mintableToken already has a buy function that probably does what you want. If you want people to be able to transfer ether directly (without calling buy), you could just rename that. Change this:

function buy() payable public {

to this:

function() payable public {

That said, I generally recommend using the fallback function when you can use a more explicit function instead, so I would recommend sticking with buy. See https://programtheblockchain.com/posts/2017/12/16/why-we-recommend-against-using-the-solidity-fallback-function/ for why I don't like the fallback function.

UPDATE

Based on the comment thread below, I'm guessing that the remaining issue is that you haven't minted any tokens. The below code (using web3.py) worked for me after deploying your contract. Note the mintToken transaction:

assert web3.eth.getBalance(contract.address) == 0

contract.transact().setPrices(700000000000000, 600000000000000)
contract.transact().mintToken(contract.address, 1)

web3.eth.sendTransaction({
    'to': contract.address,
    'value': web3.toWei(0.0006, 'ether'),
})

assert web3.eth.getBalance(contract.address) == web3.toWei(0.0006, 'ether')
assert contract.call().balanceOf(web3.eth.defaultAccount) == 1

Best Answer

Related Solutions

Solidity – Boolean Returning Method: Validate Input with “if” or require()

Contract Development – How to Automatically Transfer Ether in Token Contract

Related Topic