# Development Environment and Tools {% hint style="info" %} Before getting started, you can apply for testnet **ONG** tokens that will be used for invoking any contracts you deploy over at the [**faucet here**](https://developer.ont.io/). {% endhint %} {% hint style="warning" %} The value of gas price for a transaction must be in multiples of 10^9. The minimum value is 2500\*10^9. {% endhint %} ## Development Environment and Tools EVM smart contracts are written using [Solidity](https://docs.soliditylang.org/en/v0.8.6/). You can reuse existing Ethereum contract frameworks to develop and deploy EVM contracts. ### Remix [Remix IDE](https://remix.ethereum.org/#optimize=false\&runs=200\&evmVersion=null\&version=soljson-v0.8.1+commit.df193b15.js) is an open source development environment for EVM contracts. Remix IDE documentation is [here](https://remix-ide.readthedocs.io/en/latest/). We will now go through an example of a Hello World contract development using Remix. #### **Initialize Remix** First, locate and activate "Solidity Compiler" and "Deploy and Run Transactions" in PLUGIN MANAGER. [![image-20210526142630046](https://github.com/ontio/ontology/raw/master/docs/specifications/evm_refernce/tutorial/image-20210526142630046.png)](https://github.com/ontio/ontology/blob/master/docs/specifications/evm_refernce/tutorial/image-20210526142630046.png) Then, select Solidity environment. Create a new file and name it HelloWorld.sol. Then copy the code of [Hello World contract](https://github.com/ontio/ontology/blob/master/docs/specifications/evm_refernce/contract-demo/helloworlddemo/helloworld.sol) and paste it in the file just created. [![image-20210526143301031](https://github.com/ontio/ontology/raw/master/docs/specifications/evm_refernce/tutorial/image-20210526143301031.png)](https://github.com/ontio/ontology/blob/master/docs/specifications/evm_refernce/tutorial/image-20210526143301031.png) #### **Compile Contract** Click on the Solidity Compiler button, select compiler version to 0.5.10 and start compiling HelloWorld.sol #### **Deploy Contract** The contract is ready to deploy on Ontology after compiling. Here we deploy it on Ontology TestNet. {% hint style="info" %} **Note**: MetaMask must be configured for Ontology before you deploy the contract. {% endhint %} Select "Custom RPC" in MetaMask networks settings. Fill in and save the info below. * **Network name:** Ontology TestNet * **Node URL:** `https://polaris1.ont.io:10339` or `https://polaris2.ont.io:10339` or `https://polaris3.ont.io:10339` or `https://polaris4.ont.io:10339` * **Chain ID:** 5851 * **Blockchain Explorer URL:** "" [![RemixIDE\_Step1](https://github.com/ontio/ontology/raw/master/docs/specifications/evm_refernce/tutorial/metamask_networks.png)](https://github.com/ontio/ontology/blob/master/docs/specifications/evm_refernce/tutorial/metamask_networks.png) Finally, select "Injected Web3" in Remix. Click "Deploy" to finish. [![deploy contract](https://github.com/ontio/ontology/raw/master/docs/specifications/evm_refernce/tutorial/remix_deploy.jpg)](https://github.com/ontio/ontology/blob/master/docs/specifications/evm_refernce/tutorial/remix_deploy.jpg) #### **Invoke Contract** Now you can call the method in this contract. The string `hello` is saved in the contract when you deploy it, you can call the method `message` to query this string: [![invoke contract](https://github.com/ontio/ontology/raw/master/docs/specifications/evm_refernce/tutorial/remix_invoke.jpg)](https://github.com/ontio/ontology/blob/master/docs/specifications/evm_refernce/tutorial/remix_invoke.jpg) ### Truffle Truffle offers tools and frameworks for EVM contract development, testing and management. You can find more details [here](https://www.trufflesuite.com/docs/truffle/quickstart). Now we will demonstrate how to use Truffle with this [test code](https://github.com/ontio/ontology/blob/master/docs/specifications/evm_refernce/contract-demo/truffledemo). #### **Install Truffle** First, initialize and install dependencies. * [Node.js v8+ LTS and npm](https://nodejs.org/en/) (comes with Node) * [Git](https://git-scm.com/) Then run this command to install Truffle. ``` npm install -g truffle ``` #### **Configure truffle-config** * Create a new `.secret` to store the mnemonic phrase or private key (which can be found in MetaMask). * Edit the code of truffle-config as below. ```javascript const HDWalletProvider = require('@truffle/hdwallet-provider'); const fs = require('fs'); const mnemonic = fs.readFileSync(".secret").toString().trim(); module.exports = { networks: { ontology: { provider: () => new HDWalletProvider(mnemonic, `http://polaris2.ont.io:20339`), network_id: 5851, port: 20339, // Standard Ethereum port (default: none) timeoutBlocks: 200, gas:800000, skipDryRun: true } }, compilers: { solc: { version: "0.5.16", // Fetch exact version from solc-bin (default: truffle's version) docker: false, // Use "0.5.1" you've installed locally with docker (default: false) settings: { // See the solidity docs for advice about optimization and evmVersion optimizer: { enabled: true, runs: 200 }, evmVersion: "byzantium" } } } }; ``` #### **Deploy Contract** Run this command to deploy the contract on the Ontology network. ``` truffle migrate --network ontology ``` If successful, you will see the result below. {% hint style="warning" %} **Note:** Avoid using ETH units (e.g. wei, gwei, ether, etc.) when writing test scripts. {% endhint %} ``` Compiling your contracts... =========================== > Everything is up to date, there is nothing to compile. Starting migrations... ====================== > Network name: 'ontology' > Network id: 12345 > Block gas limit: 0 (0x0) 1_initial_migration.js ====================== Replacing 'Migrations' ---------------------- > transaction hash: 0x9019551f3d60611e1bc6b323f3cf3020d15c8aeb06833d14ff864e24622884aa > Blocks: 0 Seconds: 4 > contract address: 0x53e137A51CfD1E1b088E0d921eB5dBCF9cFa955E > block number: 6264 > block timestamp: 1624876467 > account: 0x4e7946D1Ee8f8703E24C6F3fBf032AD4459c4648 > balance: 0.00001 > gas used: 172969 (0x2a3a9) > gas price: 0 gwei > value sent: 0 ETH > total cost: 0 ETH > Saving migration to chain. > Saving artifacts ------------------------------------- > Total cost: 0 ETH 2_deploy_migration.js ===================== Replacing 'HelloWorld' ---------------------- > transaction hash: 0xf8289b96f2496a8c940ca38d736a554a90f64d927b689921781619499906721b > Blocks: 0 Seconds: 4 > contract address: 0xfbff9bd546B0e0D4b40f6f758847b70050d01b37 > block number: 6266 > block timestamp: 1624876479 > account: 0x4e7946D1Ee8f8703E24C6F3fBf032AD4459c4648 > balance: 0.00001 > gas used: 243703 (0x3b7f7) > gas price: 0 gwei > value sent: 0 ETH > total cost: 0 ETH hello contract address: 0xfbff9bd546B0e0D4b40f6f758847b70050d01b37 > Saving migration to chain. > Saving artifacts ------------------------------------- > Total cost: 0 ETH Summary ======= > Total deployments: 2 > Final cost: 0 ETH ``` ### Hardhat Hardhat is an Ethereum development environment. We will use this [test code](https://github.com/ontio/ontology/blob/master/docs/specifications/evm_refernce/contract-demo/hardhatdemo) as an example and demonstrate how to use Hardhat. #### **Install Hardhat** Please refer to [Hardhat doc](https://hardhat.org/getting-started/) for details on this step. #### **Configure hardhat-config** * Create a new `.secret` file to save your private key. * Update the code of hardhat.config.js as shown below: ```javascript require("@nomiclabs/hardhat-waffle"); const fs = require('fs'); const privateKey = fs.readFileSync(".secret").toString().trim(); module.exports = { defaultNetwork: "ontology_testnet", ontology_testnet: { url: "http://polaris2.ont.io:20339", chainId: 5851, gasPrice:2500000000000, gas:2000000, timeout:10000000, accounts: [privateKey] } }, solidity: { version: "0.8.0", settings: { optimizer: { enabled: true, runs: 200 } } }, }; ``` **Deploy Contract** Run this command in root of the project directory to deploy the contract on Ontology Chain: ``` $ npx hardhat run scripts/sample-script.js --network ontology_testnet ``` The result looks like this: ``` sss@sss hardhatdemo % npx hardhat run scripts/sample-script.js --network ontology_testnet RedPacket deployed to: 0xB105388ac7F019557132eD6eA90fB4BAaFde6E81 ``` ## Network Info ### Network Types **MainNet** | Item | Description | | -------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | NetworkName | Ontology MainNet | | chainId | 58 | | Gas Token | ONG Token | | RPC |

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| | Block Explorer | | **TestNet** | Item | Description | | -------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | NetworkName | Ontology TestNet | | chainId | 5851 | | Gas Token | ONG Token | | RPC |

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| | Block Explorer | | {% hint style="info" %} Ontology EVM contracts consume ONG as gas fee for execution. You can apply for TestNet ONG [here](https://developer.ont.io/). {% endhint %} ### EVM Assets on Ontology | Name | Address | | ---- | ------------------------------------------- | | ONG | 0x00000000000000000000000000000000000000000 | ### OEP-4 Assets Please refer to this [link](https://explorer.ont.io/tokens/oep4/10/1).