Version: Next

FLOW for Wallets & Custodians

Creating an Account

A user needs a Flow account in order to receive, hold and send FLOW tokens. The accounts & keys documentation provides a detailed overview of how accounts work on Flow.

You can create an account using templates and helper code from one of the Flow SDKs:

Create an Account with the Flow Go SDK

Receiving FLOW Deposits

Every Flow account supports the FLOW token by default. Once an account is created, it is already provisioned to receive FLOW deposits from other users.

FLOW, like any other FungibleToken on Flow, is stored in a special resource called a FungibleToken.Vault. Every new account is created with an empty FLOW vault stored at the /storage/flowTokenVault storage path.

let vault = account.borrow<&FlowToken.Vault>(from: /storage/flowTokenVault)

Conceptually, a vault is like a mailbox with a lock. Anybody can deposit tokens but only the account holder can withdraw them. This functionality is made possible by resource capabilities in Cadence. Each account publishes a FungibleToken.Receiver interface that points to its FLOW vault. The receiver is the mail slot; it allows others to deposit FLOW into a vault without stealing what's inside.

Here's how you deposit FLOW into an account:

let receiver = account
  .getCapability(/public/flowTokenReceiver)
  .borrow<&{FungibleToken.Receiver}>()
    ?? panic("Could not borrow FungibleToken.Receiver reference")
receiver.deposit(from: <-senderVault)

Detecting Deposits

The FlowToken contract emits a FlowToken.TokensDeposited event whenever tokens move between accounts.

pub event TokensDeposited(amount: UFix64, to: Address?)

You can query for this event to detect when tokens are deposited into a user's account.

Getting the Balance of an Account

Detailed below is an example of how to query the balance of a FlowToken.Vault instance.

From Cadence

Similar to the token receiver, each account publishes a FungibleToken.Balance capability that allows anybody to read the balance of an account. This allows Cadence programs to fetch the balance of an account directly in code.

let balanceRef = account
  .getCapability(/public/flowTokenBalance)
  .borrow<&FlowToken.Vault{FungibleToken.Balance}>()
    ?? panic("Could not borrow FungibleToken.Balance reference")
log(balanceRef.balance)

The above code can be executed as part of a read-only Cadence script.

From the Access API

The FLOW Access API makes it easy to query an account's balance without writing any Cadence code.

The GetAccount RPC method includes a balance field, which holds the FLOW token balance for the requested account.

import (
  "github.com/onflow/flow-go-sdk"
  "github.com/onflow/flow-go-sdk/client"
)
func main() {
  flowClient, _ := client.New(accessAPIHost)
  account, _ := flowClient.GetAccount(ctx, address)
  fmt.Println(account.Balance)
}

Sending FLOW

Below is an example of a transaction that transfers FLOW from one account to another.

import FungibleToken from 0xFUNGIBLE_TOKEN_ADDRESS
import FlowToken from 0xFLOW_TOKEN_ADDRESS
transaction(amount: UFix64, to: Address) {
  // The FungibleToken.Vault resource that holds the tokens to be transferred
  let sentVault: @FungibleToken.Vault
  prepare(sender: AuthAccount) {
    // Get a reference to the sender's stored vault
    let vault = sender.
      borrow<&ExampleToken.Vault>(from: /storage/flowTokenVault)
        ?? panic("Could not borrow reference to the owner's Vault!")
    // Withdraw tokens from the sender's stored vault
    self.sentVault <- vault.withdraw(amount: amount)
  }
  execute {
    // Get the recipient's public account object
    let recipient = getAccount(to)
    // Get a reference to the recipient's FungibleToken.Receiver
    let receiver = recipient
      .getCapability(/public/flowTokenReceiver)
      .borrow<&{FungibleToken.Receiver}>()
        ?? panic("Could not borrow receiver reference to the recipient's Vault")
    // Deposit the withdrawn tokens in the recipient's receiver
    receiver.deposit(from: <-self.sentVault)
  }
}

This transaction template is available for use in our SDKs:

Transfer Tokens with the FCL (Flow Client Library)
Coming soon: Transfer Tokens with the Go SDK

Staking FLOW

The FLOW staking documentation outlines the steps a custodian can take to support staking through a trusted node operator.

Creating an Account​

Receiving FLOW Deposits​

Detecting Deposits​

Getting the Balance of an Account​

From Cadence​

From the Access API​

Sending FLOW​

Staking FLOW​