ABI Encoder Examples

0_ABIExample.sol

pragma solidity ^0.4.24;
pragma experimental ABIEncoderV2;


contract ABIExample {

  enum Permission { ReadOnly, Write, Admin }

  struct User {
    uint256 id;
    Permission permission;
  }

  User[] users;

  constructor() public {
    users.push(User(uint256(111), Permission.Admin));
    users.push(User(uint256(222), Permission.Write));
    users.push(User(uint256(333), Permission.ReadOnly));
  }

  function getUsers() public constant returns (User[]) {
    return users;
  }

  function getUsersBytes() public constant returns (bytes) {
    User[] memory allUsers = users;
    return abi.encode(allUsers);
  }

  function set(User newUser) public {

    users.push(newUser);
  }

}

0_Caller.sol

pragma solidity ^0.4.24;


contract Caller {

    function callExternal(address _to, bytes _data)
        public
        returns (bool success)
    {
        assembly {
            success := call(not(0), _to, 0, add(_data, 0x20), mload(_data), 0, 0)
        }
    }

}

1_compile.js

// The following example is meant to be a simple self contained example.
//
// To run, paste into a node console and replace `CODE HERE` with your
// solidity code.

const ethers  = require('ethers');
const solc    = require('solc');
const ganache = require("ganache-cli");

// Provider / Signer setup.
const providers    = ethers.providers;
const web3Provider = new providers.Web3Provider(ganache.provider({ gasLimit: 6e6 }));
const signer       = web3Provider.getSigner();


// Compile the code snippets.
let contractCode           = `ABI EXAMPLE CONTRACT CODE HERE`; // Backticks for multi-line strings.
let callerContractCode     = `CALLER CONTRACT CODE HERE`;      // Backticks for multi-line strings.
let compiledContract       = solc.compile(contractCode);
let callerCompiledContract = solc.compile(callerContractCode);

let { interface, bytecode } = compiledContract.contracts[':ABIExample'];
let deployTransaction       = ethers.Contract.getDeployTransaction('0x' + bytecode, interface);
let sendPromise             = signer.sendTransaction(Object.assign(deployTransaction, { gas: 6e6 }));


// Set up Caller contract deployment.
let callerInterface         = callerCompiledContract.contracts[':Caller'].interface;
let callerBytecode          = callerCompiledContract.contracts[':Caller'].bytecode;
let deployCallerTransaction = ethers.Contract.getDeployTransaction('0x' + callerBytecode, callerInterface);
let callerSendPromise       = signer.sendTransaction(Object.assign(deployCallerTransaction, { gas: 6e6 }));

2_read.js

// The following example is meant to be a simple self contained example.
//
// To run, paste into a node console after having run 1_compile.js.

// Set up ABIExample contract deployment.
let ABIExample;
let userArray;
let userBytesArray;

sendPromise.then(res => {
    web3Provider.getTransactionReceipt(res.hash).then(res => {

        // JS contract interface.
        ABIExample = new ethers.Contract(res.contractAddress, interface, web3Provider);

        // Log result of calling the contract's `getUsers()` function.
        ABIExample.getUsers().then(res => {
            userArray = res;
            console.log('\n\n\n\nUser Array: ');
            console.log(userArray);
        });
      
        // Log result of calling the contract's `getUsersBytes()` function.
        ABIExample.getUsersBytes().then(res => {
            userBytesArray = res;
            console.log('\n\n\n\n\User Bytes Array: ');
            console.log(userBytesArray);
        });

    });
});

3_decoding.js

// The following example is meant to be a simple self contained example.
//
// To run, paste into a node console after having run 2_read.js.


let usersArrayType = ["tuple(uint256,uint8)[]"];
let decodedData    = ethers.utils.AbiCoder.defaultCoder.decode(usersArrayType, userBytesArray);

console.log(decodedData);

// Or to print nicer decodedData[0].forEach(x => console.log(`id -> ${x[0]} permission -> ${x[1]}`));

// Or if you have the abi the following would work as well.
usersArrayType = [{"components":[{"name":"id","type":"uint256"},{"name":"permission","type":"uint8"}],"name":"","type":"tuple[]"}]
decodedData    = ethers.utils.AbiCoder.defaultCoder.decode(usersArrayType, userBytesArray);

console.log(decodedData);

4_write.js

// The following example is meant to be a simple self contained example.
//
// To run, paste into a node console after having run 2_read.js.


sendPromise.then(res => {
    web3Provider.getTransactionReceipt(res.hash).then(res => {

        // New JS contract interface.
        ABIExample = new ethers.Contract(res.contractAddress, interface, signer);

        // Update state with User(444, Permission.Admin).
        ABIExample.set({ id: 444, permission: 2 }, { gasLimit: 2e5 }).then(function(transaction) {

            // Get the users array again to see the new `User` persisted.
            ABIExample.getUsers().then(res => {

                // Log the result.
                userArray = res;
                console.log('\n\n\n\n\User Bytes Array with Additional User: ');
                console.log(userArray);
            });
        });
    });
});

5_encodedWrite.js

// The following example is meant to be a simple self contained example.
//
// To run, paste into a node console after having run 2_read.js.


let userType = ["tuple(uint256,uint8)"];
let inputData = [ // AbiCoder wraps all of the data.

    [ // User tuple.
      555, // uint256 representing `id`.
      0,   // uint256 representing `permission`.
    ]

];

// Missing function sig prefix.
let encodedData = ethers.utils.AbiCoder.defaultCoder.encode(userType, inputData);

// Includes prefix using ethers.js and our contract interface.
encodedData = ABIExample.interface.functions.set({ id: 555, permission: 0 }).data;


let Caller;

callerSendPromise.then(res => {
  web3Provider.getTransactionReceipt(res.hash).then(res => {

    // New JS contract interface.
    Caller = new ethers.Contract(res.contractAddress, callerInterface, signer);

    // Update state with User(555, Permission.ReadOnly).
    Caller.callExternal(ABIExample.address, encodedData, { gasLimit: 2e5 }).then(res => {

        // Get the users array again to see the new `User` persisted.
        ABIExample.getUsers().then(res => {

            // Log result.
            userArray = res;
            console.log('\n\n\n\n\User Bytes Array with Additional User: ');
            console.log(userArray);
        });
    });
  });
});