For this assignment, we assume that we have been given the green light from the necessary legal bodies to create a crowdsale open to the public. These are the requirements that must be met:
- Set a
capto limit the maximum amount ofEtherthe company can raise. - Enable refunds
- Stablish a
goalfor the minimum amount ofEtherthe company must raise - Specify a start and end time for the crowdsale
To develop the smart contracts we refer to the OpenZeppelin library.
The PuppyCoin.sol contract inherits standards from ERC20Mintable and ERC20Detailed. Since Ethereum's default for decimals is 18, this parameter is hardcoded.
The PuppyCoinCrowdsale.sol contract inherits from the following standards:
- Crowdsale: sell tokens in exchange for Ether.
- MintedCrowdsale: tokens will be minted as purchases are made.
- CappedCrowdsale: adds a cap to the crowdsale
- TimedCrowdsale: specify start and end time
- RefundablePostDeliveryCrowdsale: tokens can be withdrawn or refunds can be claimed once the crowdsale has ended.
Inside this contract we can set parameters for all of the features of the crowdsale. Notice that only the rate, startTime, and endTime parameters are hardcoded. This contract can be customized further, but security risks should be considered at all times.
One of the most important things to cosider when creating a crowdsale is the rate. Notice that in the code the rate = .25e18. This means that one token will be issued for every 4 wei. It is very important to understand how the conversation rate works in Solidity.
We can test the crowdsale using the local network or one of the testnets. I use Kovan to test and deploy the contracts. In order to use the testnets, however, the first thing we need to do is request some test Ether from the faucets. Then follow these steps to execute the crowdsale:
1. Deploy PuppyCoinSaleDeployer contract. The crowdsale's parameters are stablished here.
2. Select PuppyCoinSale contract. Paste token_sale_address into At Address
3. Switch to PuppyCoin contract. Paste token_address into At Address button
The crowdsale should be live now.
If we are using a local network to test the crowdsale, we can use different wallets to buy tokens as we can get unlimited Ether from Ganache. Since I am limited on test Ether, I use a single account to both sell and buy tokens. The steps to follow are the same for both the local network or testnet.
1. Select the PuppyCoinSale contract and use the buyTokens function. Remember that in Solidity, math is done in the smallest of units, wei. Also, don't forget about the rate before deciding on the amount of Ether to send.
2. Tokens can be widthdrawn only when the crowdsale has been finalized by its owner. Paste the buyer's wallet address into the withdrawTokens button to retrieve tokens.
3. Using Metamask, paste the token_address to add the custom token. Make sure to be in the buyer's wallet. Tokens should be shown now.
4. The recent transactions should also be visible on the Kovan tesnet scanner
5. Custom tokens can also be added to MyCrypto (note: This only worked during local network tests)
