Smart Contract Development with Truffle

Setup Truffle project

Create a project directory and initialise the NPM project and install Truffle:

npm init

and fill in properties for you project

Now install Truffle:

npm install -g --save-dev truffle

You can also install truffle locally (without -g), but then you have to use something like (for Linux):
alias truffle=./node_modules/.bin/truffle

Now you can setup Truffle project:

truffle init

You can start your development by unboxing some of the examples e.g.:

truffle unbox tutorialtoken

or

truffle create contract YourContractName
truffle create test YourTestName

Configure Truffle for Testnet

To connect to the public RPC node we need 2 modules:

npm install --save-dev dotenv @truffle/hdwallet-provider

Now edit truffle-config.js to include:

  • the following 2 lines at the global scope:
    require('dotenv').config(); // read .env file and update process.env if present
    const HDWalletProvider = require('@truffle/hdwallet-provider');
    
  • and add the following key under the network: { key :
      testnet: {
        provider: () =>
          new HDWalletProvider(
            (process.env.PKEYS || "").split(","), // Array of account private keys
            "https://rpc.v2b.testnet.pulsechain.com"
          ),
        gas: 5000000,
        gasPrice: 50000000000,
        network_id: 941, // PulseChain Testnet network id
      },
    

    This defines a new network testnet which can be used by passed as --network testnet arguments to tuffle. Note: Check (main page)[index#Testnets] for current URL to the public PulseChain RPC.

Now create or edit .env file in your project directory to have the following content:

PKEYS="1234...98,ABCD...EF"

This file will define private keys into environment variable PKEYS passed to the HDWalletProvider instance.

Never commit or share the .env file! Although you can alternatively set PKEYS environment variable in your shell, keep in mind it may be saved with shell’s history.

Compiler version

You need to use Solidity compiler version at least 0.8.7+. You can install specific solc package like this:

npm install npm install --save-dev [email protected]

Then you need to adjust compiler version to be used in truffle-config.js under the module.exportscompilerssolcversion key.

Deploy to PulseChain

Before your start make sure you have tPLS or PLS for gas available on your account specified by the PKEYS (see above).

truffle migrate --network testnet

If you intend to verify your contract on PulseScan you have to use Windows line endings in you .sol files.

Contract verification

You can use truffle-plugin-verify to verify smart contract with PulseScan. Start by installing the plugin:

npm install --save-dev truffle-plugin-verify

Then edit your truffle-config.js and add the following under module.exports:

  plugins: ['truffle-plugin-verify'],
  api_keys: {
    etherscan: '0' // this is dummy API key, PulseScan doesn't need any, but it's required by truffle-plugin-verify.
  },

Truffle verification plugin does not support PulseChain, therefore it needs to be patched

Edit ./node_modules/truffle-plugin-verify/constants.js and:

  • add to API_URLS a new line:
    941: 'https://scan.v2b.testnet.pulsechain.com/api',
    
  • add to EXPLORER_URLS a new line:
    941: 'https://scan.v2b.testnet.pulsechain.com',
    

Finally edit ./node_modules/truffle-plugin-verify/verify.js and comment out line offset: 1 (used in function fetchConstructorValues()). PulseScan does support this argument and txlist requests would otherwise get stuck and time out.

Now you should be able to verify your contract:

truffle run verify YourContract --network testnet --debug

This command can take a while. While waiting for verification you can also check manually the Code tab on PulseScan, if the contract is shown as verified there, you can stop the command.