How to deploy a smart contract on Klaytn

The purpose of this tutorial is to set up Klaytn development environment and play around. It demonstrates one of the easiest ways to deploy a smart contract on the Klaytn network. 

First, we deploy the smart contract on the local network. 

Next, we deploy the smart contract on the Klaytn test network – Baobab. 

1. Preparation: Install the necessary tools 

We need some basic tools to get started. Lets download from the below links: 

Install git and check the version using get --version

Install docker and make sure the docker is running 

Install Node v10.21.0 or higher and check the version using node --version 

Install Jq and check the version using jq --version 

 

Now our laptop is ready for development. 

2. Download Klaytn sandbox 

Klaytn sandbox is a boilerplate code that helps developers to get started with building Dapps on Klaytn. Sandbox uses Truffle framework to compile, deploy and test smart contracts. 

Lets clone the sandbox repository, and install the necessary libraries.

git clone https://github.com/Krustuniverse-Klaytn-Group/klaytn-dev-sandbox.git 
cd klaytn-dev-sandbox 
npm install 
npm install -g truffle@v5.1.61 

Open the klaytn-dev-sandbox folder in any editor. We used VsCode in this example. You should see the below folder structure in your editor:

>contracts folder has few example smart contracts 

>migrations folder has the deployment scripts to deploy any smart contract 

>network folder has the scripts to start a local Klaytn network 

>src folder has the code to develop a UI for the Dapp 

3. Booting up a local Klaytn network 

We first need an environment where we can deploy our contracts. During development it’s a better idea to use a local blockchain which is similar to Ganache. It runs on your machine, requires no Internet and provides you with 10 test accounts to execute our transaction. 

You can easily deploy a local Klaytn network using the below command. It deploys one Klaytn consensus node by default. For more information on running a local network refer to this article

npm run run:klaytn

To see the execution logs, run npm run run:klaytn:log 

To stop the network, run npm run run:klaytn:stop 

To resume the network, run npm run run:klaytn:resume 

To completely terminate the network, run npm run run:klaytn:terminate 

To remove log files, run npm run run:klaytn:cleanlog 

4. Writing the contract

In the contracts directory of our project we can see a few example contracts to start with. Below are the standard contracts to create fungible and non-fungible tokens. We can use this example contracts to deploy in our network and transfer tokens. 

1. KIP7 similar to ERC-20 token contract 

2. KIP17 similar to ERC-721 token contract 

3. KIP37 similar to ERC-1155 contract 

In addition to the existing smart contracts we can also write our own smart contracts under the contracts folder. Here is a very simple greeter contract: 

KlaytnGreeter is a simple contract that returns a greeting message. Greeting message is set when the contract is deployed. 

pragma solidity ^0.8.0; 
contract KlaytnGreeter { 
/* Define variable greeting of the type string */ 
string greeting; 
/* This runs once when the contract is created */ 
constructor (string memory _greeting) public { 
greeting = _greeting; 
} 
/* Main function */ 
function greet() public view returns (string memory) { 
return greeting; 
} 
} 

Save the above code in a KlaytnGreeter.sol file under contracts folder. Next step is to compile and deploy the smart contract in the local network. 

5. Deploying the contract on your local network 

The Migrations directory has all the deployment scripts. By default there are deployment scripts for the token contracts. 

1. First lets try adding a deployment script for the newly created smart contract. The below code will compile and deploy the KlaytnGreeter contract in the local network and also saves the abi and deployed address in the src folder for future reference. 

const fs = require('fs') 
var greeter = artifacts.require('KlaytnGreeter') 
module.exports = function (deployer) { 
deployer.deploy(greeter, 'Welcome to Klaytn!').then(() => { 
if (greeter._json) { 
fs.mkdir('./src/deployed', { recursive: true }, (err) => { 
if (err) throw err 
}) 
// Save the deployed abi to greeterABI file in the src folder. 
fs.writeFile('./src/deployed/greeterABI', JSON.stringify(greeter._json.abi, 2), (err) => { 
if (err) throw err 
}) 
} 
// Save the deployed address to greeterAddress file in the src folder. 
fs.writeFile('./src/deployed/greeterAddress', greeter.address, (err) => { 
if (err) throw err 
console.log( 
`The deployed contract address * ${greeter.address} * is recorded on deployedAddress file` 
) 
}) 
}) 
}

We can copy the above code and save it as 5_greeter_migration.js. Now run the below command to deploy the contract.

truffle migrate --f 5 --network klaytn

You will see the below logs once it’s deployed successfully.  

2. Now lets try deploying any one of the existing sample contracts in the network. Run the below command to compile and deploy the fungible token contract.

npm run deploy:klaytn:kip7

If the deployment is successful we can see the deployed abi and address files generated under src/deployed folder. 

6. Deploying the contract on the test network 

While deploying to the test network is similar to the local network, it requires some configuration changes. Baobab is Klaytn’s test network, similar to Ropsten in Ethereum. 

The easiest way to access a testnet is via KAS (Klaytn API Service) which is a public node service similar to Infura. KAS provides access to public Klaytn nodes for testnets as well as the main network via free and paid plans. 

1. You can sign up for Klaytn API Service and get the assigned Access key and Secret key which are used to connect to the Baobab testnet. 

2. Next step is to configure truffle-config.js to update the testnet configuration.

kasBaobab: { 
provider: () => { 
const option = { 
headers: [ 
{ name: 'Authorization', value: 'Basic ' + Buffer.from(accessKeyId + ':' + secretAccessKey).toString('base64') }, { name: 'x-chain-id', value: '1001' } 
], 
keepAlive: false, 
} 
return new HDWalletProvider(privateKey, new Caver.providers.HttpProvider("https://node-api.klaytnapi.com/v1/klaytn", option)) }, 
network_id: '1001', //Klaytn baobab testnet's network id 
gas: '8500000', 
gasPrice:'25000000000' 
} 

truffle-config.js file in sandbox has the above configuration already. 

3. Add the Access key and Secret key obtained from Step1 to .env file

ACCESS_KEY_ID=KASKY9YK7JE3NEXQZN6PWT86 
SECRET_ACCESS_KEY=nO14rGPiz1QDpDdjWGcYoVTueC3ksJTcZ_eg3887 
KAS_TESTNET_API_URL=https://node-api.klaytnapi.com/v1/klaytn

4. Now we have all the configuration updates to deploy in the Baobab test network. Execute the below command to deploy.

truffle migrate --f 1 --to 2 --network kasBaobab

We can see the below output the deployed abi and address files generated under src/deployed folder.

 7. Conclusion

Congratulations on setting up a local node and deploying smart contracts. The next step is to interact with the contract. This tutorial will help in creating a frontend application. If you run into any problems, feel free to reach out to us in the Discord / Gitter channel.

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© Klaytn Foundation 2022. All rights reserved.
© Klaytn Foundation 2022. All rights reserved.