Your First Coin

This tutorial introduces how you can compile, deploy, and mint your own coin (as defined here), named MoonCoin.

Step 1: Pick an SDK

Install your preferred SDK from the below list:

Step 2: Install the CLI

Install the precompiled binary for the Aptos CLI.

Step 3: Run the example

TypeScript
Python

Clone the aptos-ts-sdk repo and build it:

git clone https://github.com/aptos-labs/aptos-ts-sdk.git
cd aptos-ts-sdk
pnpm install
pnpm build

Navigate to the TypeScript examples directory:

cd examples/typescript/

Install the necessary dependencies:

pnpm install

Run the TypeScript your_coin example:

pnpm run your_coin

The application will complete, printing:

Bob's initial MoonCoin balance: 0.
Alice mints herself 100 MoonCoin.
Alice transfers 100 MoonCoin to Bob.
Bob's updated MoonCoin balance: 100.

Clone the aptos-core repo:

git clone https://github.com/aptos-labs/aptos-core

Navigate to the Python SDK directory:

cd aptos-core/ecosystem/python/sdk

Install the necessary dependencies:

curl -sSL https://install.python-poetry.org | python3
poetry install

Run the Python your_coin example:

poetry run python -m examples.your_coin ~/aptos-core/aptos-move/move-examples/moon_coin

Step 3.1: Build the package

The example run will pause with the following output:

=== Addresses ===
Alice: 0x5e603a89cf690d7134cf2f24fdb16ba90c4f5686333721c12e835fb6c76bc7ba
Bob: 0xc8421fa4a99153f955e50f1de2a6acff2f3fd0bb33aa17ba1f5b32b699f6c825

Update the package with Alice's address, compile, and press enter.

At this point, open another terminal and change directories to the MoonCoin package’s directory:

cd ~/aptos-core/aptos-move/move-examples/moon_coin

Next, build the package using the CLI:

aptos move compile --named-addresses MoonCoin=0x5e603a89cf690d7134cf2f24fdb16ba90c4f5686333721c12e835fb6c76bc7ba --save-metadata

The --named-addresses is a list of address mappings that must be translated in order for the package to be compiled to be stored in Alice’s account. Notice how MoonCoin is set to Alice’s address printed above. Also --save-metadata is required to publish the package.

Step 3.2: Completing the example

Returning to the previous prompt, press ENTER as the package is now ready to be published.

The application will complete, printing:

Publishing MoonCoin package.

Bob registers the newly created coin so he can receive it from Alice.
Bob's initial MoonCoin balance: 0.
Alice mints Bob some of the new coin.
Bob's updated MoonCoin balance: 100.

Step 4: MoonCoin in depth

Step 4.1: Building and publishing the MoonCoin package

Move contracts are effectively a set of Move modules known as a package. When deploying or upgrading a new package, the compiler must be invoked with --save-metadata to publish the package. In the case of MoonCoin, the following output files are critical:

build/Examples/package-metadata.bcs: Contains the metadata associated with the package.
build/Examples/bytecode_modules/moon_coin.mv: Contains the bytecode for the moon_coin.move module.

These are read by the example and published to the Aptos blockchain:

TypeScript
Python

In the TypeScript example, we use aptos move build-publish-payload command to compile and build the module. That command builds the build folder that contains the package-metadata.bcs and the bytecode for the moon_coin.mv module. The command also builds a publication transaction payload and stores it in a JSON output file that we can later read from to get the metadataBytes and byteCode to publish the contract to chain with.

Compile the package:

export function compilePackage(
  packageDir: string,
  outputFile: string,
  namedAddresses: Array<{ name: string; address: AccountAddress }>,
) {
  const addressArg = namedAddresses
    .map(({ name, address }) => `${name}=${address}`)
    .join(" ");
  // Assume-yes automatically overwrites the previous compiled version, only do this if you are sure you want to overwrite the previous version.
  const compileCommand = `aptos move build-publish-payload --json-output-file ${outputFile} --package-dir ${packageDir} --named-addresses ${addressArg} --assume-yes`;
  execSync(compileCommand);
}

compilePackage("move/moonCoin", "move/moonCoin/moonCoin.json", [
  { name: "MoonCoin", address: alice.accountAddress },
]);

Publish the package to chain:

export function getPackageBytesToPublish(filePath: string) {
  // current working directory - the root folder of this repo
  const cwd = process.cwd();
  // target directory - current working directory + filePath (filePath JSON file is generated with the previous, compilePackage, CLI command)
  const modulePath = path.join(cwd, filePath);

  const jsonData = JSON.parse(fs.readFileSync(modulePath, "utf8"));

  const metadataBytes = jsonData.args[0].value;
  const byteCode = jsonData.args[1].value;

  return { metadataBytes, byteCode };
}

const { metadataBytes, byteCode } = getPackageBytesToPublish(
  "move/moonCoin/moonCoin.json",
);

// Publish MoonCoin package to chain
const transaction = await aptos.publishPackageTransaction({
  account: alice.accountAddress,
  metadataBytes,
  moduleBytecode: byteCode,
});

const pendingTransaction = await aptos.signAndSubmitTransaction({
  signer: alice,
  transaction,
});

await aptos.waitForTransaction({ transactionHash: pendingTransaction.hash });

module_path = os.path.join(
    moon_coin_path, "build", "Examples", "bytecode_modules", "moon_coin.mv"
)
with open(module_path, "rb") as f:
    module = f.read()

metadata_path = os.path.join(
    moon_coin_path, "build", "Examples", "package-metadata.bcs"
)
with open(metadata_path, "rb") as f:
    metadata = f.read()

print("\nPublishing MoonCoin package.")
package_publisher = PackagePublisher(rest_client)
txn_hash = await package_publisher.publish_package(alice, metadata, [module])
await rest_client.wait_for_transaction(txn_hash)

Step 4.2: Understanding the MoonCoin module

The MoonCoin module defines the MoonCoin struct, or the distinct type of coin type. In addition, it contains a function called init_module. The init_module function is called when the module is published. In this case, MoonCoin initializes the MoonCoin coin type as a ManagedCoin, which is maintained by the owner of the account.

module MoonCoin::moon_coin {
    struct MoonCoin {}

    fun init_module(sender: &signer) {
        aptos_framework::managed_coin::initialize<MoonCoin>(
            sender,
            b"Moon Coin",
            b"MOON",
            6,
            false,
        );
    }
}

Step 4.3: Understanding coins

Coins have several primitives:

Minting: Creating new coins.
Burning: Deleting coins.
Freezing: Preventing an account from storing coins in CoinStore.
Registering: Creating a CoinStore resource on an account for storing coins.
Transferring: Withdrawing and depositing coins into CoinStore.

Step 4.3.1: Initializing a coin

Once a coin type has been published to the Aptos blockchain, the entity that published that coin type can initialize it:

module 0x1::coin {
    public fun initialize<CoinType>(
        account: &signer,
        name: string::String,
        symbol: string::String,
        decimals: u8,
        monitor_supply: bool,
    ): (BurnCapability<CoinType>, FreezeCapability<CoinType>, MintCapability<CoinType>) {
        let account_addr = signer::address_of(account);

        assert!(
            coin_address<CoinType>() == account_addr,
            error::invalid_argument(ECOIN_INFO_ADDRESS_MISMATCH),
        );

        assert!(
            !exists<CoinInfo<CoinType>>(account_addr),
            error::already_exists(ECOIN_INFO_ALREADY_PUBLISHED),
        );

        let coin_info = CoinInfo<CoinType> {
            name,
            symbol,
            decimals,
            supply: if (monitor_supply) { option::some(optional_aggregator::new(MAX_U128, false)) } else { option::none() },
        };
        move_to(account, coin_info);

        (BurnCapability<CoinType>{ }, FreezeCapability<CoinType>{ }, MintCapability<CoinType>{ })
  }
}

This ensures that this coin type has never been initialized before. Notice the check on lines 10 and 15 to ensure that the caller to initialize is the same one that actually published this module, and that there is no CoinInfo stored on their account. If both those conditions check, then a CoinInfo is stored and the caller obtains capabilities for burning, freezing, and minting.

Step 4.3.2: Registering a coin

To use a coin, an entity must register a CoinStore for it on their account:

public entry fun registerCoinType(account: &signer) {

MoonCoin uses ManagedCoin that provides an entry function wrapper: managed_coin::register. Here is an example script for registration:

script {
    fun register(account: &signer) {
        aptos_framework::managed_coin::register<MoonCoin::moon_coin::MoonCoin>(account)
    }
}

Step 4.3.3: Minting a coin

Minting coins requires the mint capability that was produced during initialization. the function mint (see below) takes in that capability and an amount, and returns back a Coin<T> struct containing that amount of coins. If the coin tracks supply, it will be updated.

module 0x1::coin {
    public fun mint<CoinType>(
        amount: u64,
        _cap: &MintCapability<CoinType>,
    ): Coin<CoinType> acquires CoinInfo {
        if (amount == 0) {
            return zero<CoinType>()
        };

        let maybe_supply = &mut borrow_global_mut<CoinInfo<CoinType>>(coin_address<CoinType>()).supply;
        if (option::is_some(maybe_supply)) {
            let supply = option::borrow_mut(maybe_supply);
            optional_aggregator::add(supply, (amount as u128));
        };

        Coin<CoinType> { value: amount }
    }
}

ManagedCoin makes this easier by providing an entry function managed_coin::mint.

Step 4.3.4: Transferring a coin

Aptos provides several building blocks to support coin transfers:

coin::deposit<CoinType>: Allows any entity to deposit a coin into an account that has already called coin::register<CoinType>.
coin::withdraw<CoinType>: Allows any entity to extract a coin amount from their account.
aptos_account::transfer_coins<CoinType>: Transfer coins of specific CoinType to a receiver.