# Contract

CUN use EVM for contract execution.See Solidity (opens new window) for detail.

# Remix

Remix IDE (opens new window) is an open source web and desktop application. It fosters a fast development cycle and has a rich set of plugins with intuitive GUIs. Remix is used for the entire journey of contract development as well as being a playground for learning and teaching contract development.

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Create new file in file explorer. Edit contract info at right side.

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Compile contract

  1. Click compiler button, switch UI
  2. Select contract you want to compile
  3. Set compile flags
  4. Clieck compile button

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Deploy contract to blockchain via wallet such as MetaMask.

  1. Set network info in Metamask.

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  1. Back to Remix.
  • Swich environment
  • Select contract
  • click deploy button

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Deploy your contract on the chain with MetaMask

# Truffle

Use truffle to compile and deploy contract.

  • Install Node.js

See Installing Node.js (opens new window) for detail.

  • Install truffle
npm install -g truffle

Run truffle version after installation finished. If the command line displays a message like below, installation is successful.

Truffle v5.1.36 (core: 5.1.36)
Solidity v0.5.16 (solc-js)
Node v10.22.1
Web3.js v1.2.1
  • Create project

First,create folder for project.

mkdir Example
cd Example

Then, init project via truffle

truffle init

After initialization is complete, the following file structure is generated within the project.

|-- contracts         //folder for contract
|-- migrations        //folder for deployment scripts
|-- test              //folder for test document
|-- truffle-config.js //config file of truffle for this project
  • Config truffle info
const HDWalletProvider = require('@truffle/hdwallet-provider');

const fs = require('fs');
const mnemonic = fs.readFileSync(".secret").toString().trim();

module.exports = {
  networks: {
    testnet: {
      provider: () => new HDWalletProvider(mnemonic, 'https://http-testnet.coopunion.net'),
      network_id: 256
    },
    mainnet: {
      provider: () => new HDWalletProvider(mnemonic, 'https://http-mainnet.coopunion.net'),
      network_id: 114
    }
  },

  // Set default mocha options here, use special reporters etc.
  mocha: {
    // timeout: 100000
  },

  // Configure your compilers
  compilers: {
    solc: {
      // version: "0.5.1",    // Fetch exact version from solc-bin (default: truffle's version)
      // docker: true,        // 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: false,
      //    runs: 200
      //  },
      //  evmVersion: "byzantium"
      // }
    },
  },
};
  • Create contract

Put custom contracts into folder contracts and modify deployment script in folder migrations.

  • Deploy contract

Run the deployment command.

truffle migrate --network testnet

The output as below.

2_example_migration.js
======================

   Deploying 'ExampleToken'
   ------------------------
   > transaction hash:    0x91e50594a63bc6f4c299f3f445868571678be306b835bddce6dff5c7a5ddf9dc
   > Blocks: 2            Seconds: 4
   > contract address:    0x54D2049715FC8De1361D7350de90eb05F0f6CA84
   > block number:        375304
   > block timestamp:     1608016637
   > account:             0x03D32B774295D740ffEe43b20fcC0a53acC576e6
   > balance:             878.909609236165318643
   > gas used:            1056044 (0x101d2c)
   > gas price:           20 gwei
   > value sent:          0 ETH
   > total cost:          0.02112088 ETH


   > Saving migration to chain.
   > Saving artifacts
   -------------------------------------
   > Total cost:          0.02112088 ETH


Summary
=======
> Total deployments:   1
> Final cost:          0.02112088 ETH

Finally, the contract deployment is complete.

← Private Chain →