Hosted Deposit and Withdrawal - Stellar Developer Docs

This guide is available on four different programming languages: Typescript, Kotlin, Flutter (Dart) and Swift. You can change the shown version on each page via the buttons above.

The SEP-24 standard defines the standard way for anchors and wallets to interact on behalf of users. Wallets use this standard to facilitate exchanges between on-chain assets (such as stablecoins) and off-chain assets (such as fiat, or other network assets such as BTC). During the flow, a wallet makes several requests to the anchor, and finally receives an interactive URL to open in iframe. This URL is used by the user to provide an input (such as KYC) directly to the anchor. Finally, the wallet can fetch transaction information using query endpoints.

Get Anchor Information

Let’s start with getting an instance of Sep24 class, responsible for all SEP-24 interactions:

Kotlin
TypeScript
Flutter
Swift

val sep24 = anchor.sep24()

const sep24 = await anchor.sep24();

final sep24 = await anchor.sep24();

let sep24 = anchor.sep24

First, let’s get the information about the anchor’s support for SEP-24. This request doesn’t require authentication, and will return generic info, such as supported currencies, and features supported by the anchor. You can get a full list of returned fields in the SEP-24 specification.

Kotlin
TypeScript
Flutter
Swift

suspend fun getAnchorServices(): AnchorServiceInfo {
  return sep24.getServicesInfo()
}

const getAnchorServices = async (): Promise<AnchorServiceInfo> => {
  return await anchor.getServicesInfo();
};

final servicesInfo = await sep24.getServiceInfo();

let servicesInfo = try await sep24.info

Interactive Flows

Before getting started, make sure you have connected to the anchor and received an authentication token, as described in the Stellar Authentication wallet guide. We will use the authToken object in the examples below as the SEP-10 authentication token, obtained earlier. To initiate an operation, we need to know an asset. You may want to hard-code it, or get it dynamically from the anchor’s info file, like shown below (for USDC):

Kotlin
TypeScript
Flutter
Swift

val asset = info.currencies.first { it.code == "USDC" }.assetId

import { IssuedAssetId } from "@stellar/typescript-wallet-sdk";

const assetCode = "USDC";

const info = await anchor.getInfo();

const currency = info.currencies.find(({ code }) => code === assetCode);

if (!currency?.code || !currency?.issuer) {
  throw new Error(
    `Anchor does not support ${assetCode} asset or is not correctly configured on TOML file`,
  );
}

const asset = new IssuedAssetId(currency.code, currency.issuer);

final asset = info.currencies.firstWhere((it)=>it.code=='USDC').assetId;

let info = try await anchor.info
let asset = try info.currencies?.first(where: {$0.code == "USDC"})?.assetId

Before starting with the deposit flow, make sure that the user account has established a trustline for the asset you are working with.

Basic Flow

Let’s start with a basic deposit:

Kotlin
TypeScript
Flutter
Swift

val deposit = sep24.deposit(asset, authToken)

const deposit = await sep24.deposit({
  assetCode: asset.code,
  authToken,
});

final deposit = await sep24.deposit(asset, authToken);

let deposit = try await sep24.deposit(assetId: asset, authToken: authToken)

As a result, you will get an interactive response from the anchor. Open the received URL in an iframe and save the transaction ID for future reference:

Kotlin
TypeScript
Flutter
Swift

val url = deposit.url
val id = deposit.id

const url = deposit.url;
const id = deposit.id;

final url = deposit.url;
final id = deposit.id;

let url = deposit.url
let id = deposit.id

Similarly to the deposit flow, a basic withdrawal flow has the same method signature and response type:

Kotlin
TypeScript
Flutter
Swift

val withdrawal = sep24.withdraw(asset, authToken)
val url = withdrawal.url
val id = withdrawal.id

const withdrawal = await sep24.withdraw({
  assetCode: asset.code,
  authToken,
});
const url = withdrawal.url;
const id = withdrawal.id;

final withdrawal = await sep24.withdraw(asset, authToken);
final url = withdrawal.url;
final id = withdrawal.id;

let withdrawal = try await sep24.withdraw(assetId: asset, authToken: authToken)
let url = withdrawal.url
let id = withdrawal.id

Providing KYC Info

To improve the user experience, the SEP-24 standard supports passing user KYC to the anchor via SEP-9. In turn, the anchor will pre-fill this information in the interactive popup.

While SEP-9 supports passing binary data, the current version of the SDK doesn’t offer such functionality.

At the time, accepted SEP-9 is not strictly typed yet. Improved typing will be offered in future versions.

Kotlin
TypeScript
Flutter
Swift

val sep9 = mapOf("email_address" to "[email protected]")

val deposit = sep24.deposit(asset, authToken, sep9)

const deposit = await sep24.deposit({
  assetCode: asset.code,
  authToken,
  extraFields: { email_address: "[email protected]" },
});

final deposit = await sep24.deposit(asset, authToken,
  extraFields: {"email_address": "[email protected]"});

let deposit = try await sep24.deposit(assetId: asset,
                                      authToken: authToken,
                                      extraFields: ["email_address" : "[email protected]"])

Changing Stellar Transfer Account

By default, the Stellar transfer will be sent to the authenticated account (with a memo) that initiated the deposit. While in most cases it’s acceptable, some wallets may split their accounts. To do so, pass additional account (and optionally a memo):

Kotlin
TypeScript
Flutter
Swift

suspend fun depositDifferentAccount(): InteractiveFlowResponse {
  val recipientAccount = "G..."
  val memo = "my memo" to MemoType.TEXT
  return sep24.deposit(asset, authToken, destinationAccount = recipientAccount, destinationMemo = memo)
}

import { Memo, MemoText } from "@stellar/stellar-sdk";

const recipientAccount = "G...";
const depositDifferentAccount = async (): Promise<InteractiveFlowResponse> => {
  return await sep24.deposit({
    destinationAccount: recipientAccount,
    destinationMemo: new Memo(MemoText, "some memo"),
    assetCode: asset.code,
    authToken,
  });
};

final recipientAccount = "G...";
final deposit = await sep24.deposit(asset, authToken, destinationAccount: recipientAccount,
  destinationMemo: "my memo", destinationMemoType: MemoType.text);

let recipientAccount = "G..."
let deposit = try await sep24.deposit(assetId: asset,
                                      authToken: authToken,
                                      destinationAccount: recipientAccount,
                                      destinationMemo: "my memo",
                                      destinationMemoType: MemoType.text)

Similarly, for a withdrawal, the origin account of the Stellar transaction could be changed:

Kotlin
TypeScript
Flutter
Swift

val originAccount = "G..."
val withdrawal = sep24.withdraw(asset, authToken, withdrawalAccount = originAccount)

const originAccount = "G...";
const withdrawal = await sep24.withdraw({
  withdrawalAccount: originAccount,
  assetCode: asset.code,
  authToken,
});

final originAccount = "G...";
final withdrawal = await sep24.withdraw(asset, authToken, withdrawalAccount: originAccount);

let originAccount = "G..."
let withdrawal = try await sep24.withdraw(assetId: asset,
                                          authToken: authToken,
                                          withdrawalAccount: originAccount)

Getting Transaction Info

On the typical flow, the wallet would get transaction data to notify users about status updates. This is done via the SEP-24 GET /transaction and GET /transactions endpoint. Alternatively, some anchors support webhooks for notifications. Note that this feature is not widely adopted yet.

Tracking Transaction

Let’s look into how to use the wallet SDK to track transaction status changes. We will use Watcher class for this purpose. First, let’s initialize watcher and start tracking a transaction.

Kotlin
TypeScript
Flutter
Swift

val watcher = sep24.watcher()
val result = watcher.watchOneTransaction(authToken, "transaction id")

const watcher = sep24.watcher();

const { stop, refresh } = watcher.watchOneTransaction({
  authToken,
  assetCode: asset.code,
  id: successfulTransaction.id,
  onMessage,
  onSuccess,
  onError,
});

final watcher = sep24.watcher();
final result = watcher.watchOneTransaction(authToken, "transaction id");

let watcher = sep24.watcher()
let result = watcher.watchOneTransaction(authToken: authToken,
                                         id: "transaction id")

Alternatively, we can track multiple transactions for the same asset.

Kotlin
TypeScript
Flutter
Swift

val watcher = sep24.watcher()
val result = watcher.watchAsset(getAuthToken(), asset)

Next, let’s get the channel provided by WatcherResult to receive events.

do {
  val event = result.channel.receive()
  when (event) {
    is StatusChange ->
      println("Status changed to ${event.status}. Transaction: ${event.transaction}")
    is ExceptionHandlerExit -> println("Exception handler exited the job")
    is ChannelClosed -> println("Channel closed. Job is done")
  }
} while (event !is ChannelClosed)

This code example will consume all events coming from the channel until it’s closed. There are three types of events:

StatusChange: indicates that transaction status has changed.
ExceptionHandlerExit: indicates that the exception handler exited the processing loop. With default retry handler it happens when retries are exhausted.
ChannelClosed: indicates that the channel is closed and no more events will be emitted. This event will always fire. If ExceptionHandlerExit happened, channel will close right after. Otherwise, (under normal circumstances) it will stop when all transactions reach terminal statuses.

Events are stored in the channel until they are received, and calling the receive() method will block the channel until a message is received. You can read more about how channels work in the channel documentation.

const watcher = sep24.watcher();

const { stop, refresh } = watcher.watchAllTransactions({
  authToken,
  assetCode: asset.code,
  onMessage,
  onError,
});

final watcher = sep24.watcher();
final result = watcher.watchAsset(authToken, asset);

let watcher = sep24.watcher()
let result = watcher.watchAsset(authToken: authToken, asset: asset)

Fetching Transaction

While Watcher class offers powerful tracking capabilities, sometimes it’s required to just fetch a transaction (or transactions) once. The Anchor class allows you to fetch a transaction by ID, Stellar transaction ID, or external transaction ID:

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// "id" is the actual Anchor transaction id, all transactions should have it.
val transaction = sep24.getTransactionBy(authToken, id = "transaction id")

// "stellarTransactionId" (aka "stellar_transaction_id" on the SEP spec)
// is the hash of the Stellar network transaction payment related to this
// Anchor transaction.
// The "stellarTransactionId" has a SHA256 hash format like the below:
// - "a35135d8ed4b29b66d821444f6760f8ca1e77bea1fb49541bebeb2c3d844364a"
// E.g. we'll only have this transaction id field AFTER the wallet sends funds
// to Anchor on the withdrawal flow or receives funds from Anchor on the
// deposit flow.
val transaction = sep24.getTransactionBy(authToken, stellarTransactionId = "transaction id")

// "externalTransactionId" (aka "external_transaction_id" on the SEP spec)
// could refer to some ID of transaction on external network.
// E.g. this could be some "reference number" displayed to the user on
// the last step of the Interactive Flow UI which the user could use in some
// other external place to complete the deposit or withdraw operation.
val transaction = sep24.getTransactionBy(authToken, externalTransactionId = "transaction id")

const transaction = await sep24.getTransactionBy({
  authToken,
  id: transactionId,
});

// "id" is the actual Anchor transaction id, all transactions should have it.
const transaction = await anchor.sep24().getTransactionBy({
  authToken,
  id: transactionId,
});

// "stellarTransactionId" (aka "stellar_transaction_id" on the SEP spec)
// is the hash of the Stellar network transaction payment related to this
// Anchor transaction.
// The "stellarTransactionId" has a SHA256 hash format like the below:
// - "a35135d8ed4b29b66d821444f6760f8ca1e77bea1fb49541bebeb2c3d844364a"
// E.g. we'll only have this transaction id field AFTER the wallet sends funds
// to Anchor on the withdrawal flow or receives funds from Anchor on the
// deposit flow.
const transaction = await anchor.sep24().getTransactionBy({
  authToken,
  stellarTransactionId,
});

// "externalTransactionId" (aka "external_transaction_id" on the SEP spec)
// could refer to some ID of transaction on external network.
// E.g. this could be some "reference number" displayed to the user on
// the last step of the Interactive Flow UI which the user could use in some
// other external place to complete the deposit or withdraw operation.
const transaction = await anchor.sep24().getTransactionBy({
  authToken,
  externalTransactionId,
});

final transaction = await sep24.getTransaction("transaction id", authToken);

// "transactionId" is the actual Anchor transaction id, all transactions should have it.
let transaction = try await anchor.sep24.getTransactionBy(authToken: authToken,
                                                          transactionId: "transaction id")

// "stellarTransactionId" (aka "stellar_transaction_id" on the SEP spec)
// is the hash of the Stellar network transaction payment related to this
// Anchor transaction.
// The "stellarTransactionId" has a SHA256 hash format like the below:
// - "a35135d8ed4b29b66d821444f6760f8ca1e77bea1fb49541bebeb2c3d844364a"
// E.g. we'll only have this transaction id field AFTER the wallet sends funds
// to Anchor on the withdrawal flow or receives funds from Anchor on the
// deposit flow.
let transaction = try await anchor.sep24.getTransactionBy(authToken: authToken,
                                                          stellarTransactionId: "stellar transaction id")

// "externalTransactionId" (aka "external_transaction_id" on the SEP spec)
// could refer to some ID of transaction on external network.
// E.g. this could be some "reference number" displayed to the user on
// the last step of the Interactive Flow UI which the user could use in some
// other external place to complete the deposit or withdraw operation.
let transaction = try await anchor.sep24.getTransactionBy(authToken: authToken,
                                                          externalTransactionId: "external transaction id")

It’s also possible to fetch transaction by the asset

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val transactions = sep24.getTransactionsForAsset(asset, authToken)

const transactions = await sep24.getTransactionsForAsset({
  authToken,
  assetCode: asset.code,
});

final transactions = await sep24.getTransactionsForAsset(asset, authToken);

let transactions = try await sep24.getTransactionsForAsset(authToken: authToken, asset: asset)

Submitting Withdrawal Transfer

Previously, we took a look at starting the withdrawal flow. Now, let’s take a look at a full example. First, start the withdrawal:

Kotlin
TypeScript
Flutter
Swift

val withdrawal = sep24.withdraw(asset, authToken)

const withdrawal = await sep24.withdraw({
  assetCode: asset.code,
  authToken,
});

final withdrawal = await sep24.withdraw(asset, authToken);

let withdrawal = try await sep24.withdraw(assetId: asset, authToken: authToken)

Next, open an interactive url :

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TypeScript
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val url = withdrawal.url
// open the url

const url = withdrawal.url;
// open the url

final url = withdrawal.url
// open the url

let url = withdrawal.url
// open the url

After that we need to wait until the anchor is ready to receive funds. To do so, we will be waiting until transaction reaches pending_user_transfer_start status. This code uses a simple watching (polling) mechanism with no bail-out condition. The application’s code should be more robust.

Kotlin
TypeScript
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val withdrawalWatcher = sep24.watcher().watchOneTransaction(authToken, withdrawal.id)
var statusChange: StatusUpdateEvent

// Wait for user input
do {
  statusChange = withdrawalWatcher.channel.receive()
} while (
  ((statusChange as? StatusChange) ?: throw Exception("Channel unexpectedly closed"))
    .status != TransactionStatus.PENDING_USER_TRANSFER_START
)

const watcher = sep24.watcher();

const onMessage = (transaction) => {
  if (transaction.status === "pending_user_transfer_start") {
    // begin transfer code
  }
};

const onSuccess = (transaction) => {
  // transaction comes back as completed / refunded / expired
};

const onError = (transaction) => {
  // runtime error, or the transaction comes back as
  // no_market / too_small / too_large / error
};

// We can watch for a particular transaction.
const { refresh, stop } = watcher.watchOneTransaction({
  authToken,
  assetCode: asset.code,
  id: successfulTransaction.id,
  onMessage,
  onSuccess,
  onError,
});

// Or watch for ALL transactions of a particular asset.
const { refresh, stop } = watcher.watchAllTransactions({
  authToken,
  assetCode: asset.code,
  onMessage,
  onError,
});

final withdrawalWatcher = sep24.watcher().watchOneTransaction(authToken, withdrawal.id);
withdrawalWatcher.controller.stream.listen(
  (event) {
    if (event is StatusChange && TransactionStatus.pendingUserTransferStart == event.status) {
      // begin transfer
    }
  },
  onError: (error) {
    // handle error
  },
);

let watcher = anchor.sep24.watcher()
let result = watcher.watchOneTransaction(authToken: authToken,
                                         id: withdrawal.id)

NotificationCenter.default.addObserver(self,
                                       selector: #selector(handleEvent(_:)),
                                       name: result.notificationName,
                                       object: nil)

/// ...
@objc public func handleEvent(_ notification: Notification) {
    if let statusChange = notification.object as? StatusChange {
        print("Status change to \(statusChange.status.rawValue). Transaction: \(statusChange.transaction.id)")
        if statusChange.status == TransactionStatus.pendingUserTransferStart {
          // begin transfer
        }
    } else if let _ = notification.object as? ExceptionHandlerExit {
        print("Exception handler exited the job")
    } else if let _ = notification.object as? NotificationsClosed {
        print("Notifications closed. Job is done")
    }
}

Next, sign and submit the Stellar transfer:

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val anchorTransaction = (statusChange.transaction as WithdrawalTransaction)
val transfer = stellar.transaction(keypair).transferWithdrawalTransaction(anchorTransaction, asset).build()

transfer.sign(keypair)

stellar.submitTransaction(transfer)

// Import Horizon to get the result codes for error handling
import { Horizon } from "@stellar/stellar-sdk";

// This creates a transaction builder which we'll be using to assemble
// our transfer withdrawal transaction as shown below.
const txBuilder = await stellar.transaction({
  sourceAddress: keypair,
  baseFee: 10000, // this is 0.001 XLM
  timebounds: 180, // in seconds
});

// We can use the transaction object received on the onMessage callback from
// the watcher, or, we can also fetch the transaction object using either
// getTransactionBy or getTransactionsForAsset as illustrated in previous step.
onMessage: (transaction) => {
  if (transaction.status === "pending_user_transfer_start") {
    // Use the builder to assemble the transfer transaction. Behind the scenes
    // it extracts the Stellar account (withdraw_anchor_account), memo (withdraw_memo)
    // and amount (amount_in) to use in the Stellar payment transaction that will
    // be submitted to the Stellar network.
    const transferTransaction = txBuilder
      .transferWithdrawalTransaction(transaction, asset)
      .build();

    // Signs it with the account key pair
    transferTransaction.sign(keypair);

    // Finally submits it to the Stellar network. This stellar.submitTransaction()
    // function handles '504' status codes (timeout) by keep retrying it until
    // submission succeeds or we get a different error.
    try {
      const response = await stellar.submitTransaction(transferTransaction);
      console.log("Stellar-generated transaction ID: ", response.id);
    } catch (error) {
      /*
        In case it's not a 504 (timeout) error, the application could try some
        resolution strategy based on the error kind.

        On Stellar docs you can find a page dedicated to error handling:
        https://developers.stellar.org/docs/learn/encyclopedia/errors-and-debugging

        And status/result codes:
        https://developers.stellar.org/docs/data/apis/horizon/api-reference/errors
      */

      // Let's illustrate here how we could handle an 'invalid sequence number' error.

      // We can access all possible result codes through Horizon's API.
      const sdkResultCodes = Horizon.HorizonApi.TransactionFailedResultCodes;

      // We can access error's response data to check for useful error details.
      const errorData = error.response?.data;
      /*
        Sample of errorData object returned by the Wallet SDK:
        {
          type: 'https://stellar.org/horizon-errors/transaction_failed',
          title: 'Transaction Failed',
          status: 400,
          detail: 'The transaction failed when submitted to the Stellar network.
            The `extras.result_codes` field on this response contains further details.
            Descriptions of each code can be found at:
            https://developers.stellar.org/docs/data/apis/horizon/api-reference/errors/http-status-codes/horizon-specific/transaction-failed',
          extras: {
            envelope_xdr: 'AAAAAgAAAADBjF7n9gfByOwlnyaJH...k4BRagf/////////8AAAAAAAAAAA==',
            result_codes: { transaction: 'tx_bad_seq' },
            result_xdr: 'AAAAAAAAAGT////6AAAAAA=='
          }
        }
      */

      /*
        Example scenario: invalid sequence numbers.

        These errors typically occur when you have an outdated view of an account.
        This could be because multiple devices are using this account, you have
        concurrent submissions happening, or other reasons. The solution is relatively
        simple: retrieve the account details and try again with an updated sequence number.
      */
      if (
        errorData?.status == 400 &&
        errorData?.extras?.result_codes?.transaction ===
          sdkResultCodes.TX_BAD_SEQ
      ) {
        // Creating a new transaction builder means retrieving an updated sequence number.
        const txBuilder2 = await stellar.transaction({
          sourceAddress: keypair,
          baseFee: 10000,
          timebounds: 180,
        });

        // ...

        // Repeat all the steps until submitting the transaction again.

        // ...

        const response2 = await stellar.submitTransaction(transferTransaction);
        console.log(
          "Stellar-generated transaction ID on retry: ",
          response2.id,
        );

        // The application should take care to not resubmit the same transaction
        // blindly with an updated sequence number as it could result in more than
        // one payment being made when only one was intended.
      }
    }
  }
};

final tx = event.transaction as WithdrawalTransaction;

final paymentBuilder = flutter_sdk.PaymentOperationBuilder(
  tx.withdrawAnchorAccount!,
  flutter_sdk.Asset.createNonNativeAsset(asset.code, asset.issuer),
  tx.amountIn!,
);

final transactionBuilder = flutter_sdk.TransactionBuilder(sourceAccount)
  ..addOperation(paymentBuilder.build());

flutter_sdk.Memo? memo;
if ("text" == tx.withdrawalMemoType) {
  memo = flutter_sdk.MemoText(tx.withdrawalMemo!);
} else if ("hash" == tx.withdrawalMemoType) {
  memo = flutter_sdk.MemoHash(base64Decode(tx.withdrawalMemo!));
} // ... etc.

if (memo != null) {
  transactionBuilder.addMemo(memo);
}

flutter_sdk.KeyPair kp =
  flutter_sdk.KeyPair.fromSecretSeed(userKeyPair.secretKey);
final transaction = transactionBuilder.build()..sign(kp, network);
final paymentResult = await sdk.submitTransaction(transaction);

if let tx = statusChange.transaction as? WithdrawalTransaction {
    let paymentOperation = try PaymentOperation(sourceAccountId: sourceAccountId,
                                                destinationAccountId: tx.withdrawAnchorAccount!,
                                                asset: asset.toAsset(),
                                                amount: Decimal(string:tx.amountIn!)!)
    var memo:Memo? = nil
    if "text" == tx.withdrawalMemoType {
        memo = Memo.text(tx.withdrawalMemo!)
    } else if "hash" == tx.withdrawalMemoType {
        memo = Memo.hash(Data(base64Encoded: tx.withdrawalMemo!)!)
    } // ...etc

    let transaction = try Transaction(sourceAccount: sourceAccount,
                                      operations: [paymentOperation],
                                      memo: memo)

    let keypair = try KeyPair(secretSeed: userKeyPair.secretKey)
    try transaction.sign(keyPair: keypair, network: Network.public)
    let server = wallet.stellar.server
    let paymentResult = await server.transactions.submitTransaction(transaction: transaction)
}

Where keypair is the SEP-10 authenticated account. If you want to transfer funds from a different address, refer to Changing Stellar Transfer Account section. Code for submitting transactions to Stellar should be developed thoughtfully. The SDF has a documentation page dedicated to submitting transactions and handling errors gracefully. Here are a few things you need to keep in mind:

Offer a high fee. Your fee should be as high as you would offer before deciding the transaction is no longer worth sending. Stellar will only charge you the minimum necessary to be included in the ledger — you won’t be charged the amount you offer unless everyone else is offering the same amount or greater. Otherwise, you’ll pay the smallest fee offered in the set of transactions included in the ledger.
Set a maximum timebound on the transaction. This ensures that if your transaction is not included in a ledger before the set time, you can reconstruct the transaction with a higher offered fee and submit it again with better chances of inclusion.
Resubmit the transaction when you get 504 status codes. 504 status codes are just telling you that your transaction is still pending — not that it has been canceled or that your request was invalid. You should simply make the request again with the same transaction to get a final status (either included or expired).

Finally, let’s track transaction status updates. In this example we simply check if the transaction has been completed:

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TypeScript
Flutter
Swift

var terminalStatus: TransactionStatus? = null

do {
  statusChange = withdrawalWatcher.channel.receive()

  when (statusChange) {
    is StatusChange -> {
      if (statusChange.status.isTerminal()) {
        terminalStatus = statusChange.status
      }
    }
    is ChannelClosed -> println("Transaction tracking finished")
    is ExceptionHandlerExit ->
      println("Retries exhausted trying obtain transaction data, giving up.")
  }
} while (statusChange !is ChannelClosed)

if (terminalStatus != TransactionStatus.COMPLETED) {
  println("Transaction was not completed")
}

const watcher = sep24.watcher();

const onSuccess = (transaction) => {
  // transaction came back as completed / refunded / expired
  console.log("Transaction is completed");
};

const onError = (transaction) => {
  // runtime error, or the transaction comes back as
  // no_market / too_small / too_large / error
};

const { refresh, stop } = watcher.watchOneTransaction({
  authToken,
  assetCode: asset.code,
  id: successfulTransaction.id,
  onMessage,
  onSuccess,
  onError,
});

final watcher = sep24.watcher().watchOneTransaction(authToken, withdrawal.id);
watcher.controller.stream.listen(
  (event) {
    if (event is StatusChange && event.status.isTerminal()) {
      if (TransactionStatus.completed != event.status) {
        print("Transaction was not completed!");
      } else {
        print("Success");
      }
    } else if (event is ExceptionHandlerExit) {
      print("Retries exhausted trying obtain transaction data, giving up.");
    } else if (event is StreamControllerClosed) {
      print("Transaction tracking finished");
    }
  },
  onError: (error) {
    // handle error
  },
);

let watcher = anchor.sep24.watcher()
let result = watcher.watchOneTransaction(authToken: authToken,
                                         id: withdrawal.id)

NotificationCenter.default.addObserver(self,
                                       selector: #selector(handleEvent(_:)),
                                       name: result.notificationName,
                                       object: nil)

/// ...
@objc public func handleEvent(_ notification: Notification) {
    if let statusChange = notification.object as? StatusChange {
        if statusChange.status != TransactionStatus.completed {
          print("Transaction was not completed!")
        } else {
          print("Success")
        }
    } else if let _ = notification.object as? ExceptionHandlerExit {
        print("Exception handler exited the job")
    } else if let _ = notification.object as? NotificationsClosed {
        print("Notifications closed. Job is done")
    }
}

​Get Anchor Information

​Interactive Flows

​Basic Flow

​Providing KYC Info

​Changing Stellar Transfer Account

​Getting Transaction Info

​Tracking Transaction

​Fetching Transaction

​Submitting Withdrawal Transfer

Get Anchor Information

Interactive Flows

Basic Flow

Providing KYC Info

Changing Stellar Transfer Account

Getting Transaction Info

Tracking Transaction

Fetching Transaction

Submitting Withdrawal Transfer