Part 1/4 in a series on collateralizing ERC721s for loans on Dharma Protocol

mintERC721.js

/********************
 *  Setup Dharma.js *
 *******************/

// Instantiate Dharma
const dharma = new Dharma();

/********************
 *  Mint an ERC721  *
 *******************/

/**
 * Define an address for a debtor who will own the collateral on the blockchain.
 * Replace this with an address that you own, such as your MetaMask account address.
 */
const DEBTOR_ADDRESS = "0x601e6e7711b9e3b1b20e1e8016038a32dfc86ddd";
// Define some amount of max gas to use in the transactions.
const MAX_GAS = 4712388;
// We use the two above variables to define default transaction arguments.
const TX_DEFAULTS = {
    from: DEBTOR_ADDRESS,
    gas: MAX_GAS,
};

// Load a deployed ERC721 contract that has the ability to mint tokens.
console.log("Loading the ERC721 contract...");
dharma.contracts.loadMintableERC721ContractAsync(TX_DEFAULTS).then(async (erc721) => {
    // Find out the number of tokens that have been minted thus far.
    const numTokens = await erc721.totalSupply.callAsync();
    console.log(
        `The ERC721 contract has loaded. There have been ${numTokens} tokens minted so far.`
    );
    // We can use the number of tokens as the token's ID, which will be unique as
    // long as we increment it by one each time we mint a token. It's also okay to use
    // a randomly generated token ID.
    const tokenId = numTokens;
    console.log(
        `Attempting to create token with ID: ${tokenId}. Please approve the transaction.`
    );
    // Mint a new token and transfer it to the debtor's address defined above.
    let txHash = await erc721.mint.sendTransactionAsync(DEBTOR_ADDRESS, tokenId);

    console.log("Waiting for the transaction to be mined (may take a while)e...");
    // Wait for this transaction to be mined before proceeding to the next step.
    await dharma.blockchain.awaitTransactionMinedAsync(txHash);

    // Let's confirm that it was created.
    const tokenExists = await erc721.exists.callAsync(tokenId);
    if (!tokenExists) {
        throw new Error("Something went wrong and the token doesn't exist!");
    }

    /*
     * Once this has completed, the debtor will have an ERC721 token that they can use
     * for collateral for a loan on Dharma Protocol.
     *
     * Log the ID of the token, and save it so we can use it when creating the debt order.
     */
    console.log(`New token minted with ID: ${tokenId.toString()}`);

    /********************************
     *  Collateralization Approval  *
     ********************************/

    // Load the contract that will hold this ERC721 token as collateral when order is filled.
    console.log("Loading collateralizer contract...");
    const collateralizerContract = await dharma.contracts.loadERC721CollateralizerAsync();
    const collateralizerAddress = collateralizerContract.address;

    // We need to grant the collateralizer contract the ability to lock our ERC721
    // as collateral when the debt order is eventually filled.
    console.log(
        "Please approve the transaction to give the " +
        "collateralizer contract access to the collateral."
    );
    txHash = await erc721.approve.sendTransactionAsync(
        collateralizerAddress,
        tokenId,
    );

    // Wait for this transaction to be mined before checking the approvals are correct.
    console.log("Waiting for the transaction to be mined (may take a while)...");
    await dharma.blockchain.awaitTransactionMinedAsync(txHash);

    // Let's confirm that we have the correct approval.
    const approvedAddress = await erc721.getApproved.callAsync(tokenId);
    const collateralizerApproved = (approvedAddress === collateralizerAddress);
    if (!collateralizerApproved) {
        throw new Error(
            "Something went wrong and the collateralizer doesn't have approval yet!"
        );
    }
    console.log("The collateralizer has approval for collateralization!");
});