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Hands-on 1

Connect to Metamask to authenticate and display the user's wallet address and possessed DEV

First, I will introduce the finished product to be created this time. Please access the following URL

This application is an application that connects to Metamask, authenticates, and displays the user's wallet address and possessed DEV.

[Explanation of operation]

Please access the following URL and open CodeSandbox.

Select src / index.ts from Explore on the left to display the source code.

If you scroll to the bottom, you will find ①. From now on, I will code from ① to ⑨.

①: Here, the link between the click event of the button and the clickLoginButton method, and the code of the processing when the button is pressed are written. (2): The clickLoginButton method accesses Metamask, performs authentication processing, and displays the user's wallet address and possessed DEV. It is a method that does up to. ③: From ③ to ⑦, judge the status of Metamask to determine if you are logged in. The following is defined as the state of Metamask

Login judgmentMetaMask stateExplanation
Not logged inMetamask not installedThe browser does not have Metamask installed
Not logged inNot connected to MetamaskWebsite is not allowed to connect with Metamask
Not logged inNot logged in with MetamaskNot logged in on Metamask
Not logged inMetamask connection network is differentThe network to which Metamask connects is different from the network your website expects
LoginNot applicable to the above conditionsYou can get the wallet address from Metamask and connect to the network that the website expects.

In ③, it is judged that "Metamask is not installed". Scroll to find the isMetamask function. Code the isMetamask function as follows:

function isMetamask(): boolean {
return !!window.ethereum && !!window.ethereum.isMetaMask

When metamask is installed in your browser, ethereum will be added to the window object. Using this as a judgment material, it returns whether "Metamask is not installed".

④: Next, determine "Not connected to Metamask". Scroll down to find the connectMetaMask function. Code the connectMetaMask function as follows:

async function connectMetaMask(): Promise<boolean> {
try {
await window.ethereum.request({ method: 'eth_requestAccounts' })
} catch (e) {
if (e.code === 4001) {
return false
return true

To determine "not connected to Metamask", query the address of Ethereum from Metamask. At that time, if the connection between the website and Metamask cannot be established, such as when the user refuses to connect with Metamask, a 4001 code error will be returned, so this is used for judgment. refer to:

⑤: Next, determine "not logged in with Metamask". Scroll down to find the isMetaMaskLogin function. Code the isMetaMaskLogin function as follows:

async function isMetaMaskLogin(): Promise<boolean> {
return !!(await getAccount())

The isMetaMaskLogin function calls the getAccount function. The getAccount function gets the wallet address from Metamask and returns it. Code the getAccount function as follows:

async function getAccount() {
const accounts = (await window.ethereum.request({
method: 'eth_accounts',
})) as string[]

return accounts[0]

⑥: Next, determine "the state where the connection network of Metamask is different". Scroll down to find the isMainNet function. Code the isRopsten function as follows:

function isRopsten() {
return parseInt(window.ethereum.chainId) === 3

window.ethereum.childId returns the following CHAIN_ID depending on the network you are connecting to

Mainnet1Ethereum production environment network
Ropsten3Ethereum Test Network (PoW)
Rinkeby4Ethereum Test Network (PoA)

refer to:

⑦: If the checks from ③ to ⑥ do not catch the item, it is considered as "logged in". After this, we will code the post-login process.

⑧: Next, get the user's wallet address and display it. Scroll to find ⑧ and code as follows.

const walletAddress = await getAccount()
const addressElement = document.getElementById('address')
addressElement.innerText = walletAddress

The getAccount function created in ⑤ is used to get the wallet address.

⑨: Next, acquire the user's possessed DEV and display it. Scroll to find the getBalanceOfDEV function. Code the getBalanceOfDEV function as follows:

import { addresses, contractFactory } from '@devprotocol/dev-kit'
import { BigNumber } from '@ethersproject/bignumber'
import Web3 from 'web3'

async function getBalanceOfDEV(walletAddress: string) {
const provider = new Web3(window.ethereum)
const client = contractFactory(provider.currentProvider)

const registryContract = client.registry(addresses.eth.ropsten.registry)

const addressDEV = await registryContract.token()

const amountBigNumber = BigNumber.from(

const amount = amountBigNumber.div('1000000000000000000').toString()
return amount
  • Add await when calling getBalanceOfDEV

contractFactory is a function declared in @ devprotocol / dev-kit, and you can create a client by passing the currentProvider of Web3 as an argument. You can use this client to operate the Dev Protocol. This time, we are using client to get the number of possessed DEVs.

const registryContract = client.registry(addresses.eth.ropsten.registry)

Dev Protocol contracts are distributed by type, and the address of each contract is managed by registryContract. In the above part, we are getting the registryContract of the ropsten environment. DevProtocol has main and ropsten environments. In the above part, we are getting the registryContract of the ropsten environment. DevProtocol has main and ropsten environments.

const addressDEV = await registryContract.token()

In this hands-on, we want to display the number of DEVs we have, so we are returning the address of the token contract that handles DEV tokens.

const amountBigNumber = BigNumber.from(

The dev function is a method for contracts related to DEV tokens. By setting the contract address of the DEV token in the dev function and specifying the wallet address of the target person in the balanceOf method, the number of DEVs possessed by the target person is returned.

In addition to the dev function, client has the following functions.

export type DevkitContract = {
readonly allocator: ReturnType<typeof createAllocatorContract>
readonly market: ReturnType<typeof createMarketContract>
readonly property: ReturnType<typeof createPropertyContract>
readonly propertyFactory: ReturnType<typeof createPropertyFactoryContract>
readonly lockup: ReturnType<typeof createLockupContract>
readonly withdraw: ReturnType<typeof createWithdrawContract>
readonly dev: ReturnType<typeof createDevContract>
readonly registry: ReturnType<typeof createRegistryContract>
readonly policy: ReturnType<typeof createPolicyContract>
readonly policyGroup: ReturnType<typeof createPolicyGroupContract>
readonly metrics: ReturnType<typeof createMetricsContract>
readonly policyFactory: ReturnType<typeof createPolicyFactoryContract>


In addition to the balanceOf function, the dev function has the following functions.

export type DevContract = {
readonly totalSupply: () => Promise<string>
readonly balanceOf: (address: string) => Promise<string>
readonly transfer: (to: string, value: string) => Promise<boolean>
readonly allowance: (from: string, to: string) => Promise<string>
readonly approve: (to: string, value: string) => Promise<boolean>
readonly transferFrom: (
from: string,
to: string,
value: string
) => Promise<boolean>
readonly name: () => Promise<string>
readonly symbol: () => Promise<string>
readonly decimals: () => Promise<string>
readonly deposit: (to: string, value: string) => Promise<boolean>
readonly contract: () => Contract


const amount = amountBigNumber.div('1000000000000000000').toString()

Since the decimal point of the ERC20 token is 18 digits, it is divided to match the decimal point.

This is the end of coding. Let's check the operation. When you can log in and your wallet address and the number of DEVs you have are displayed on the screen, you are done.