Package Exports

@makerdao/multicall

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Readme

Multicall.js

Multicall.js is a lightweight JavaScript library for interacting with the multicall smart contract.

yarn add @makerdao/multicall

-- or --

npm install @makerdao/multicall

Multicall allows multiple calls to constant functions to be grouped into a single call and the results aggregated into a single result from the multicall contract. This reduces the number of separate JSON RPC requests that need to be sent over the network if using a remote node like Infura, and the assurance that all values returned are from the same block. (The latest block number is returned along with the aggregated results.)

Currently supported data types are: booleans, integers, addresses, fixed-size byte arrays (e.g. bytes32)

Summary

Get the return value from different smart contract function calls in a single call
Assurance that all values are from the same block number / block height
Compare the returned block number against the previous call's block number to know if it's possible for any returned values to be different (i.e. for polling)

Usage

import MultiCall from "@makerdao/multicall";
const multicall = new MultiCall('kovan'); // kovan or mainnet

const { blockNumber, mkrBalance, priceFeed } = await multicall.aggregate([
    // MKR balance of some address
    {
        to: '0xAaF64BFCC32d0F15873a02163e7E500671a4ffcD',
        method: 'balanceOf(address)',
        args:  [['0x72776bb917751225d24c07d0663b3780b2ada67c', 'address']],
        returns: [['mkrBalance', 'uint256']]
    },
    // address of the ETH:USD price feed used Maker's cdp engine
    {
        to: '0xa71937147b55Deb8a530C7229C442Fd3F31b7db2',
        method: 'pip()',
        returns: [['priceFeed', 'address']]
    },
    // ... etc, many more value reads are possible w/ this request
]) // all of these calls happen w/ a single call to some node

Examples

First use npm or yarn to install the dependencies:

yarn install

Then run an example from the examples folder:

yarn examples

Test

To run tests use:

yarn test