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Run a simple dApp that uses Blocto wallet service

Hello World

Let's build a simple project that sends a simple transaction on Flow testnet with Blocto FCL wallet.

You need to have Node.js and yarn installed for the rest of the tutorial.

Step 1 - Create app and setup dependencies

$ npx create-react-app hello-world

In the hello-world folder you've just created, install dependencies necessary for this project.

$ yarn add @blocto/fcl@^1.4.0
$ yarn add styled-components

FCL is under heavy developments and the versions are not always backward compatible. We recommend that you use @blocto/fcl@^1.4.0 for now.

You can start the app and see it running on http://localhost:3000

$ yarn start

Step 2 - Read from Flow

  1. Create src/GetLatestBlock.js

  2. Add the component to src/App.js

  3. Add config for FCL in src/index.js so FCL knows which access node to read data from

import React, {useState} from "react"
import * as fcl from "@blocto/fcl"
import styled from 'styled-components'

const Card = styled.div`
  margin: 10px 5px;
  padding: 10px;
  border: 1px solid #c0c0c0;
  border-radius: 5px;
`

const Code = styled.pre`
  background: #f0f0f0;
  border-radius: 5px;
  max-height: 150px;
  overflow-y: auto;
  padding: 5px;
`

const GetLatestBlock = () => {
  const [data, setData] = useState(null)

  const runGetLatestBlock = async (event) => {
    event.preventDefault()

    const response = await fcl.send([
      fcl.getBlock(true)
    ])
    
    setData(await fcl.decode(response))
  }

  return (
    <Card>
      <button onClick={runGetLatestBlock}>
        Get Latest Block
      </button>
      
      {data && <Code>{JSON.stringify(data, null, 2)}</Code>}
    </Card>
  )
}

export default GetLatestBlock

When user clicks the button, runGetLatestBlock sends a request to get information for the latest block on Flow and display the result in <Code> block.

Step 3 - Connect to Blocto wallet

Now, let's add login functionality to your dApp.

  1. Create src/Authenticate.js

  2. Add the component to src/App.js

  3. Add config for FCL in src/index.js so FCL knows which wallet to use

import React, {useState, useEffect} from "react"
import styled from "styled-components"
import * as fcl from "@blocto/fcl"

const Card = styled.div`
  margin: 10px 5px;
  padding: 10px;
  border: 1px solid #c0c0c0;
  border-radius: 5px;
`

const SignInOutButton = ({ user: { loggedIn } }) => {
  const signInOrOut = async (event) => {
    event.preventDefault()

    if (loggedIn) {
      fcl.unauthenticate()
    } else {
      fcl.authenticate()
    }
  }

  return (
    <button onClick={signInOrOut}>
      {loggedIn ? 'Sign Out' : 'Sign In/Up'}
    </button>
  )
}

const CurrentUser = () => {
  const [user, setUser] = useState({})

  useEffect(() =>
    fcl
      .currentUser()
      .subscribe(user => setUser({...user}))
  , [])

  return (
    <Card>
      <SignInOutButton user={user} />
    </Card>
  )
}

export default CurrentUser

When user clicks the login button, FCL calls out to Blocto wallet and the user can either register a new Blocto account or login to their existing Blocto accounts. Once the login process completes and user chooses to use the Blocto account on the dApp, the dApp gets the connected account information and show it in <UserProfile>.

Step 4 - Send a simple transaction

Finally, we can use the connected Blocto Flow account to send a transaction.

  1. Create src/SendTransaction.js

  2. Add the component to src/App.js

import React, {useState} from "react"
import * as fcl from "@blocto/fcl"
import styled from 'styled-components'

const Card = styled.div`
  margin: 10px 5px;
  padding: 10px;
  border: 1px solid #c0c0c0;
  border-radius: 5px;
`

const Header = styled.div`
  font-size: 16px;
  font-weight: 600;
  margin-bottom: 5px;
`

const Code = styled.pre`
  background: #f0f0f0;
  border-radius: 5px;
  max-height: 300px;
  overflow-y: auto;
  padding: 5px;
`

const simpleTransaction = `\
transaction {
  execute {
    log("Hello World!!")
  }
}
`

const SendTransaction = () => {
  const [status, setStatus] = useState("Not started")
  const [transaction, setTransaction] = useState(null)

  const sendTransaction = async (event) => {
    event.preventDefault()
    
    setStatus("Resolving...")

    const blockResponse = await fcl.send([
      fcl.getLatestBlock(),
    ])

    const block = await fcl.decode(blockResponse)
    
    try {
      const tx = await fcl.send([
        fcl.transaction(simpleTransaction),
        fcl.proposer(fcl.currentUser().authorization),
        fcl.payer(fcl.currentUser().authorization),
        fcl.ref(block.id),
        fcl.limit(100)
      ])

      const { transactionId } = tx

      setStatus(`Transaction (${transactionId}) sent, waiting for confirmation`)

      const unsub = fcl
        .tx(transactionId)
        .subscribe(transaction => {
          setTransaction(transaction)

          if (fcl.tx.isSealed(transaction)) {
            setStatus(`Transaction (${transactionId}) is Sealed`)
            unsub()
          }
        })
    } catch (error) {
      console.error(error)
      setStatus("Transaction failed")
    }
  }

  return (
    <Card>
      <Header>send transaction</Header>

      <Code>{simpleTransaction}</Code>

      <button onClick={sendTransaction}>
        Send
      </button>

      <Code>Status: {status}</Code>

      {transaction && <Code>{JSON.stringify(transaction, null, 2)}</Code>}
    </Card>
  )
}

export default SendTransaction

When user clicks the send button, FCL summons Blocto wallet and prompts user to either approve the transaction or reject it. If user approves of the transaction, Blocto wallet signs the message with the key in custodial and pass the signature back to FCL, where the transaction and the signature is sent to Flow network.

Awesome! You have sent a transaction to Flow testnet with Blocto wallet!

Other Resources

PreviousFlowNextConfigure FCL

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