transferCrypto

How to call the API from an app

Hedera Wallet Snap connects to your currently connected Metamask account by default. To learn how apps can connect to Hedera Wallet Snap using a non-metamask(external) account, refer to this documentation.

Then, depending on whether you're trying to connect to a metamask account or a non-metamask account, you can call the snap API in the following way:

const snapId = `npm:@hashgraph/hedera-wallet-snap`

const transferCryptoAPI = async () => {
  const externalAccountParams = {
    externalAccount: {
      accountIdOrEvmAddress: '0.0.12345',
      curve: 'ED25519'
    }
  }

  const transfers = [
    {
      assetType: 'HBAR', // 'HBAR' | 'TOKEN' | 'NFT'
      to: '0.0.4498148',
      amount: 1,
      assetId?, // You must pass in a Token ID or NFT Id for transferring tokens
      from?,    // This can be passed if you're trying to do a delegated transfer
    }
  ]

  // If you're sending to an exchange account, 
  // you will likely need to fill this out
  const memo = '' 

  await window.ethereum.request({
    method: 'wallet_invokeSnap',
    params: {
      snapId,
      request: {
        method: 'transferCrypto',
        params: {
          network: 'testnet',
          transfers,
          memo,
          maxFee: undefined
          /* 
            Uncomment the below line if you want to connect 
            to a non-metamask account
          */
          // ...externalAccountParams
        }
      }
    }
  })
}

If you pass an 'undefined' value to maxFee, the snap uses the maximum possible value as maxFee

What the API does

1. Retrieves the currently connected account the user has selected on Metamask. If it's the first time, a new snap account is created and the account info is saved in snap state.

2. Parses the arguments that were passed such as the asset to transfer, who to transfer to and the amount to transfer.

3. Calls the Hedera SDK Transfer Cryptocurrency API to transfer hbar, tokens, nfts, etc. It can also be used to do a delegate transfer if the account has another account approved to spend tokens on its behalf.

4. Send the asset to the receiver address

5. Returns the transaction receipt as response

An example response:

{
  "currentAccount": {
    "hederaAccountId": "0.0.4559",
    "hederaEvmAddress": "0x3ba201df50314e4702d4d92b52d304ee63bfca23",
    "balance": {
      "hbars": 89.60505513,
      "timestamp": "Thu, 01 Feb 2024 21:22:58 GMT",
      "tokens": {}
    },
    "network": "testnet"
  },
  "receipt": {
    "status": "SUCCESS",
    "accountId": "",
    "fileId": "",
    "contractId": "",
    "topicId": "",
    "tokenId": "",
    "scheduleId": "",
    "exchangeRate": {
      "hbars": 1,
      "cents": 12,
      "expirationTime": "Mon, 25 Nov 1963 17:31:44 GMT",
      "exchangeRateInCents": 12
    },
    "topicSequenceNumber": "0",
    "topicRunningHash": "",
    "totalSupply": "0",
    "scheduledTransactionId": "",
    "serials": [],
    "duplicates": [],
    "children": []
  }
}

Live Demo on CodePen

Some things to keep in mind while interacting with the above demo

• If you're getting any errors with the live demo, make sure you go through the FAQs section to learn about what you may be missing. You need to install Metamask in your browser for the live demo to work

To ease the integration of Hedera Wallet Snap on an application, we have created a template web application that you can run locally and check out the code in its entirety to learn how you can integrate and interact with various APIs exposed by Hedera Wallet Snap. Check out the full source code at template application github repository.

You can also check out the API reference to learn how each API works.