5. Deploy Contract

1) Get some testnet KLAY to deploy contract 2) Truffle configuration 3) Deploy setup (select contract which you want to deploy) 4) Deploy

1) Get some KLAY

To deploy contract, we need some KLAY in your account to pay for gas price. You can get 5 KLAY via Klaytn Wallet in the testnet. 1. Create your Klaytn account at Baobab Klaytn Wallet -> PRIVATE KEY will be used in truffle configuration. So copy it down somewhere 2. After creating your Klaytn account, run faucet to receive 5 Baobab testnet KLAY in Baobab Klaytn Faucet

2) truffle configuration

truffle-config.js is a configuration file including deployment configuration. We are going to deploy our contract using Private key we've just created in the previous step. Paste your Private key that has enough KLAY to truffle-config.js

WARNING: You shouldn't expose your private key. Otherwise, your account would be hacked.

// truffle-config.js

const HDWalletProvider = require("truffle-hdwallet-provider-klaytn");

/**
 * truffle network variables
 * for deploying contract to klaytn network.
 */
const NETWORK_ID = '1001'

/**
 * URL: URL for the remote node you will be using
 * PRIVATE_KEY: Private key of the account that pays for the transaction (Change it to your own private key)
 */
const URL = 'http://localhost:8551'

// Paste your `Private key` that has enough KLAY to truffle.js
const PRIVATE_KEY = '0x3de0c90ce7e440f19eff6439390c29389f611725422b79c95f9f48c856b58277'

module.exports = {
  networks: {
    klaytn: {
      provider: () => new HDWalletProvider(PRIVATE_KEY, URL),
      network_id: NETWORK_ID,
      gas: '8500000',
      gasPrice: null,
    },
  },

  // Specify the version of compiler, we use 0.5.6
  compilers: {
    solc: {
      version: '0.5.6',
    },
  },
}

networks property

See networks property above. klaytn network has 4 properties, provider, network_id, gas, gasPrice.

• provider: () => new HDWalletProvider(PRIVATE_KEY, URL) Just as the name indicates, it injects private key and url defined above.

• network_id: NETWORK_ID Specify network id in Klaytn, you should set it to 1001 to use Klaytn Baobab network (testnet).

• gas: GASLIMIT Maximum gas you are willing to spend.

• gasPrice: null This is price per every gas unit. Currently in Klaytn, the gas price is fixed to '25000000000'. By setting it to null, truffle will automatically set the gas price.

compiler property

Remember that for Solidity contract we used version 0.5.6, thus specify compiler version here.

3) Deployment setup

migrations/2_deploy_contracts.js:

const Klaystagram = artifacts.require('./Klaystagram.sol')
const fs = require('fs')

module.exports = function (deployer) {
  deployer.deploy(Klaystagram)
    .then(() => {
    if (Klaystagram._json) {
      // 1. Record recently deployed contract's abi file to 'deployedABI'
      fs.writeFile(
        'deployedABI',
        JSON.stringify(Klaystagram._json.abi, 2),
        (err) => {
          if (err) throw err
          console.log(`The abi of ${Klaystagram._json.contractName} is recorded on deployedABI file`)
        })
    }

    // 2. Record recently deployed contract's address to 'deployedAddress'
    fs.writeFile(
      'deployedAddress',
      Klaystagram.address,
      (err) => {
        if (err) throw err
        console.log(`The deployed contract address * ${Klaystagram.address} * is recorded on deployedAddress file`)
    })
  })
}

You can specify which contract code will you deploy in your contracts/ directory.

1. Import your contract file (Klaystagram.sol) via

   const Klaystagram = artifacts.require('./Klaystagram.sol')

2. Use deployer to deploy your contract, deployer.deploy(Klaystagram).

3. If you want to add more logic after deploying your contract, use .then() (optional)

4. To save contracts' deployedABI and deployedAddress, use fs node.js module

   fs.writeFile(filename, content, callback) (optional)

cf. For further information about artifacts.require(), refer to truffle official documentation at truffle docs

4) Deploy

In your terminal type $ truffle deploy --network klaytn. It will deploy your contract according to truffle-config.js and migrations/2_deploy_contracts.js configuration.

Terminal will display deployed contract address if deployment was successful.

cf) --reset option If you provide this option, truffle will recompile and redeploy your contract even if contracts haven't changed. ex) $ truffle deploy --reset --network klaytn