link

Link is a scala.js example that demonstrate how to interact with an ethereum blockchain from scala code compiled to JS code and running within a browser. Starting from there you can develop you ethereum application in pure scala. Nice isn't it?

This application takes the web3 object either from a web3 capable browser (MIST, MetaMask, Parity...) if not it falls back using uport-connect. It lets the user query and transact with a contract deployed on the rinkeby ethereum test network. To get some test net ethers, go to the rinkeby faucet.

It is still a very early stage :). To test it:

sbt assemble # whenever you update the scala code
cd truffle
npm install # only the first time
npm run dev

Now you can browse http://localhost:3000. You need a web3 enabled browser or metamask.

Deploy the smart contract on a local node:

npm install -g ethereumjs-testrpc
testrpc
cd truffle
truffle migrate --reset --network development

Deploy the smart contract on Rinkeby test net:

Start a geth node on Rinkeby

cd docker
docker-compose up --build
docker exec -it docker_geth_1 geth attach ipc://root/.ethereum/rinkeby/geth.ipc

You're now in a JavaScript console, you need to:

• retrieve your (newly created) account address
• get toy Ether from the Rinkeby faucet
• unlock your account to enable truffle to use it to deploy the smart contract

var address = personal.listAccounts[0]
address // copy paste this for rinkeby faucet

Visit Rinkeby faucet and follow their instructions to make your address (previously copied) known to their service. Go back to your geth JavaScript console when done.

eth.getBalance(address) // check you received the funds
personal.unlockAccount(address)

Finally deploy the contract from a regular shell console:

cd ../truffle
truffle migrate --reset --network rinkeby

Troubleshooting

• Cannot deploy smart contract: rm -rf truffle/build

Enjoy !

The mid term plan is to fully map the web3.js API.