themacexpert / dappcon

DappCon 2022 Workshop

Building Cross Chain DApps with Moonbeam @DappCon 2022

This guide contains all the links you'll need for the workshop. We won't assume any pre-existing account setup, so we will start from a blank slate.

Send a message to another chain with Axelar

In this demo, we will use Axelar's General message passing to call a contract on another chain. We will be mostly following the steps of this blog post guide, with the exception of the gas amounts, which have changed since the publish date.

To get started, first copy and paste the contents of SimpleGeneralMessage.sol into Remix.

The required gas amounts in WEI to send along with the message from Moonbase Alpha are the following:

• Polygon Mumbai: 339003286300000000
• Avalanche Fuji: 970363238301000000
• Fantom Testnet: 553898649000000000
• Ethereum Ropst: 16000000000000000000

Initial Setup

1. Install MetaMask
2. Add Moonbase Alpha Network to MetaMask
3. Import ALICE Account into your MetaMask. This is a Shared Public Test Account that's already funded with plenty of testnet funds. Private Key: 0x28194e8ddb4a2f2b110ee69eaba1ee1f35e88da2222b5a7d6e3afa14cf7a3347

Remote Execution with XCM

Initial Setup

1. Install MetaMask
2. Add Moonbase Alpha Network to MetaMask
3. Get funds from the faucet
4. Swap some (not all) DEV tokens for xcUNITS

Calculating a Sovereign Address

• Clone the xcmTools repo
• Shawn Tabrizi's Utilities

Account Setup

• Create a New Account on the Moonbase Relay Chain
• Import the ALICE Account on the Moonbase Alpha Parachain Private Key: 0x28194e8ddb4a2f2b110ee69eaba1ee1f35e88da2222b5a7d6e3afa14cf7a3347
• Also, import the ALICE account to your MetaMask

Calculating the Derivative Account

• Clone the PolkaTools repo
• Check account balance of derivative account

Transfer

• Fill out the transfer information on the relay chain to get the call bytes but don't submit here
• Initiate the remote transfer transaction on the Moonbase Alpha Parachain
• Parameters you'll need include:
• Index: 42
• Foreign Asset ID: 42259045809535163221576417993425387648
• Weight: 1000000000

Using XCMTransactor.sol

• Access the precompile here:
• Copy and paste it into remix
• Calculate the external XC-20 address
• Verify the address on Moonbase Alpha Moonscan