The Cloud Functions for Firebase client SDKs let you call functions directly from
a Firebase app. To call a function from your app in this way, write and deploy
an HTTP Callable function in Cloud Functions, and
then add client logic to call the function from your app.

It's important to keep in mind that HTTP callable functions are similar but
**not identical to** HTTP functions. To use HTTP callable functions you must
use the client SDK for your platform together with the
backend API (or implement the protocol). Callables have these key
difference from HTTP functions:

- With callables, Firebase Authentication tokens, FCM tokens, and App Check tokens, when available, are automatically included in requests.
- The trigger automatically deserializes the request body and validates auth tokens.

The Firebase SDK for Cloud Functions 2nd gen and higher interoperates with these Firebase client
SDK minimum versions to support HTTPS Callable functions:

- Firebase SDK for Apple platforms 13.1.1
- Firebase SDK for Android 23.0.0
- Firebase Modular Web SDK v. 9.7.0

If you want to add similar functionality to an app built on an unsupported
platform, see the [Protocol Specification for `https.onCall`](https://firebase.google.com/docs/functions/callable-reference.md.txt). The rest of this guide provides
instructions on how to write, deploy, and call
an HTTP callable function for Apple platforms, Android, web, C++, and Unity.

> [!WARNING]
> **Experimental:** HTTP callable functions now have experimental support for Dart. [Learn more](https://firebase.google.com/docs/functions/start-dart.md.txt) about building a full-stack Dart application using the new Cloud Functions and Admin SDKs for Dart.

## Write and deploy the callable function

Code examples in this section are based on a complete
[quickstart sample](https://github.com/firebase/functions-samples/tree/main/Node/quickstarts/callable-functions)
that demonstrates how to send requests to a server-side function and get a
response using one of the Client SDKs. To get started, import the required
modules:

### Node.js

```javascript
// Dependencies for callable functions.
const {onCall, HttpsError} = require("firebase-functions/https");
const {logger} = require("firebase-functions");

// Dependencies for the addMessage function.
const {getDatabase} = require("firebase-admin/database");
const sanitizer = require("./sanitizer");
```

### Python

```python
# Dependencies for callable functions.
from firebase_functions import https_fn, options

# Dependencies for writing to Realtime Database.
from firebase_admin import db, initialize_app
```

### Dart (experimental)

```dart
// Dependencies for callable functions.
import 'package:firebase_functions/firebase_functions.dart';
```

Use the request handler for your platform
to create an HTTPS callable function. This method
takes a request parameter:

### Node.js

```javascript
// Saves a message to the Firebase Realtime Database but sanitizes the
// text by removing swearwords.
exports.addmessage = onCall((request) => {
  // ...
});
```

### Python

```python
@https_fn.on_call()
def addmessage(req: https_fn.CallableRequest) -> Any:
    """Saves a message to the Firebase Realtime Database but sanitizes the text
    by removing swear words."""
```

### Dart (experimental)

```dart
// Adds two numbers to each other.
firebase.https.onCall(name: 'addNumbers', (request, response) async {
```

The `request` parameter contains data passed from the client app as well as additional context like authentication state. For a callable function that saves a text message to the Realtime Database,
for example, `data` could contain the message text, along with auth information
in `auth`:

### Node.js

```javascript
// Message text passed from the client.
const text = request.data.text;
// Authentication / user information is automatically added to the request.
const uid = request.auth.uid;
const name = request.auth.token.name || null;
const picture = request.auth.token.picture || null;
const email = request.auth.token.email || null;
```

### Python

```python
# Message text passed from the client.
text = req.data["text"]
# Authentication / user information is automatically added to the request.
uid = req.auth.uid
name = req.auth.token.get("name", "")
picture = req.auth.token.get("picture", "")
email = req.auth.token.get("email", "")
```

### Dart (experimental)

```dart
// Numbers passed from the client.
final data = request.data as Map<String, Object?>?;
final firstNumber = data?['firstNumber'];
final secondNumber = data?['secondNumber'];
// Authentication / user information is automatically added to the request.
final uid = request.auth?.uid;
final token = request.auth?.token;
final name = token?['name'];
final picture = token?['picture'];
final email = token?['email'];

// Use variables to suppress 'unused' lint warnings
print(
  'User details: uid=$uid, name=$name, picture=$picture, email=$email',
);
```

> [!NOTE]
> **Note:** Sample code for the experimental Dart SDK is based on a simpler sample that does not interact with Realtime Database or other features not yet supported during the experimental release.

Distance between the location of the callable function and the location
of the calling client can create network latency. To optimize performance,
consider specifying the [function location](https://firebase.google.com/docs/functions/locations.md.txt) where
applicable, and make sure to align the callable's location with the location
set when you [initialize the SDK](https://firebase.google.com/docs/functions/callable.md.txt#initialize-client)
on the client side.

Optionally, you can attach an App Check attestation to help protect your
backend resources from abuse, such as billing fraud or phishing. See
[Enable App Check enforcement for Cloud Functions](https://firebase.google.com/docs/app-check/cloud-functions.md.txt).

> [!NOTE]
> **Note:** Use only the [`functions.https`](https://firebase.google.com/docs/reference/functions/2nd-gen/node/firebase-functions.https.md.txt) or [`firebase_functions.https_fn`](https://firebase.google.com/docs/reference/functions/2nd-gen/python/firebase_functions.https_fn.md.txt) backend APIs to write callable functions. The HTTP trigger API is entirely separate and not interoperable with callable functions.

### Send back the result

To send data back to the client, return data that can be JSON encoded. For
example, to return the result of an addition operation:

### Node.js

```javascript
// returning result.
return {
  firstNumber: firstNumber,
  secondNumber: secondNumber,
  operator: "+",
  operationResult: firstNumber + secondNumber,
};
```

### Python

```python
return {
    "firstNumber": first_number,
    "secondNumber": second_number,
    "operator": "+",
    "operationResult": first_number + second_number,
}
```

### Dart (experimental)

```dart
// returning result.
return CallableResult({
  'firstNumber': firstNumber,
  'secondNumber': secondNumber,
  'operator': '+',
  'operationResult': firstNumber + secondNumber,
});
```

The sanitized text from the message text example is returned both to the client
and to the Realtime Database. In Node.js, this can be done
asynchronously using a JavaScript promise:

### Node.js

```javascript
// Saving the new message to the Realtime Database.
const sanitizedMessage = sanitizer.sanitizeText(text); // Sanitize message.

return getDatabase().ref("/messages").push({
  text: sanitizedMessage,
  author: {uid, name, picture, email},
}).then(() => {
  logger.info("New Message written");
  // Returning the sanitized message to the client.
  return {text: sanitizedMessage};
})
```

### Python

```python
# Saving the new message to the Realtime Database.
sanitized_message = sanitize_text(text)  # Sanitize message.
db.reference("/messages").push(
    {  # type: ignore
        "text": sanitized_message,
        "author": {"uid": uid, "name": name, "picture": picture, "email": email},
    }
)
print("New message written")

# Returning the sanitized message to the client.
return {"text": sanitized_message}
```

Your function must return a value or, in the case of Node.js, a Promise that
resolves with a value. Otherwise, the function may terminate
before data is sent back to the client. See [Terminate functions](https://firebase.google.com/docs/functions/terminate-functions.md.txt)
for guidance.

### Send and receive streaming results

[Video](https://www.youtube.com/watch?v=PDr7dbbFQnI)

Callable functions have mechanisms for handling streaming results. If you have a
use case that requires streaming, you can configure streaming in the callable
request and then use the appropriate method from the client SDK to call the
function.

#### Send streaming results

To efficiently stream results that are generated over time, such as from a
number of separate API requests or a generative AI API, check the
`acceptsStreaming` property on your callable request. When this property is set
to `true`, you can stream results back to the client with
`response.sendChunk()`.

For example, if an app needed to retrieve weather forecast data for multiple
locations, the callable function could send each location's forecast separately
to clients that have requested a streaming response, instead of making them wait
until all forecast requests have resolved:

```javascript
exports.getForecast = onCall(async (request, response) => {
  if (request.data?.locations?.length < 1) {
    throw new HttpsError("invalid-argument", "Missing locations to forecast");
  }

  // fetch forecast data for all requested locations
  const allRequests = request.data.locations.map(
      async ({latitude, longitude}) => {
        const forecast = await weatherForecastApi(latitude, longitude);
        const result = {latitude, longitude, forecast};

        // clients that support streaming will have each
        // forecast streamed to them as they complete
        if (request.acceptsStreaming) {
          response.sendChunk(result);
        }

        return result;
      },
  );

  // Return the full set of data to all clients
  return Promise.all(allRequests);
});
```

Note that the way `response.sendChunk()` operates depends on certain details of
the client's request:

1. If the client requests a streaming response: `response.sendChunk(data)`
   sends the data piece immediately.

2. If the client does not request a streaming response: `response.sendChunk()`
   does nothing for that call. The full response is sent once all data is ready.

To determine whether the client is requesting a streaming response, check the
`request.acceptsStreaming` property. For example, if `request.acceptsStreaming`
is false, you might decide to skip any resource-intensive work specifically
related to preparing or sending individual chunks, as the client isn't expecting
an incremental delivery.

#### Receive streaming results

In a typical scenario, the client requests streaming with the `.stream` method
and then iterates through the results:

### Swift

```swift
func listenToWeatherForecast() async throws {
    isLoading = true
    defer { isLoading = false }

    Functions
      .functions(region: "us-central1")
    let getForecast: Callable<WeatherRequest, StreamResponse<WeatherResponse, [WeatherResponse]>> = Functions.functions().httpsCallable("getForecast")

    let request = WeatherRequest(locations: locations)
    let stream = try getForecast.stream(request)

    for try await response in stream {
      switch response {
      case .message(let singleResponse):
        weatherData["\(singleResponse.latitude),\(singleResponse.longitude)"] = singleResponse
      case .result(let arrayOfResponses):
        for response in arrayOfResponses {
          weatherData["\(response.latitude),\(response.longitude)"] = response
        }
        print("Stream ended.")
        return
      }
    }
  }
```

### Web

```javascript
// Get the callable by passing an initialized functions SDK.
const getForecast = httpsCallable(functions, "getForecast");

// Call the function with the `.stream()` method to start streaming.
const { stream, data } = await getForecast.stream({
  locations: favoriteLocations,
});

// The `stream` async iterable returned by `.stream()`
// will yield a new value every time the callable
// function calls `sendChunk()`.
for await (const forecastDataChunk of stream) {
  // update the UI every time a new chunk is received
  // from the callable function
  updateUi(forecastDataChunk);
}

// The `data` promise resolves when the callable
// function completes.
const allWeatherForecasts = await data;
finalizeUi(allWeatherForecasts);
```

Loop through the `stream` async iterable as shown. Awaiting the `data`
promise indicates to the client that the request is complete

### Kotlin

```kotlin
// Get the callable by passing an initialized functions SDK.
val getForecast = functions.getHttpsCallable("getForecast");

// Call the function with the `.stream()` method and convert it to a flow
getForecast.stream(
  mapOf("locations" to favoriteLocations)
).asFlow().collect { response ->
  when (response) {
    is StreamResponse.Message -> {
      // The flow will emit a [StreamResponse.Message] value every time the
      // callable function calls `sendChunk()`.
      val forecastDataChunk = response.message.data as Map<String, Any>
      // Update the UI every time a new chunk is received
      // from the callable function
      updateUI(
        forecastDataChunk["latitude"] as Double,
        forecastDataChunk["longitude"] as Double,
        forecastDataChunk["forecast"] as Double,
      )
    }
    is StreamResponse.Result -> {
      // The flow will emit a [StreamResponse.Result] value when the
      // callable function completes.
      val allWeatherForecasts = response.result.data as List<Map<String, Any>>
      finalizeUI(allWeatherForecasts)
    }
  }
}
```

In order to use the `asFlow()` extension function, add the
`org.jetbrains.kotlinx:kotlinx-coroutines-reactive` library as a
dependency to the app's `build.gradle(.kts)` file.

### Java

```java
// Get the callable by passing an initialized functions SDK.
HttpsCallableReference getForecast = mFunctions.getHttpsCallable("getForecast");
getForecast.stream(
  new HashMap<String, Object>() {{
    put("locations", favoriteLocations);
  }}
).subscribe(new Subscriber<StreamResponse>() {
  @Override
  public void onSubscribe(Subscription subscription) {
    subscription.request(Long.MAX_VALUE);
  }

  @Override
  public void onNext(StreamResponse streamResponse) {
    if (streamResponse instanceof StreamResponse.Message) {
      // The flow will emit a [StreamResponse.Message] value every time the
      // callable function calls `sendChunk()`.
      StreamResponse.Message response = (StreamResponse.Message) streamResponse;
      Map<String, Object> forecastDataChunk =
        (Map<String, Object>) response.getMessage().getData();
      // Update the UI every time a new chunk is received
      // from the callable function
      updateUI(
        (double) forecastDataChunk.get("latitude"),
        (double) forecastDataChunk.get("longitude"),
        (double) forecastDataChunk.get("forecast")
      );
    } else if(streamResponse instanceof StreamResponse.Result) {
      // The flow will emit a [StreamResponse.Result] value when the
      // callable function completes.
      StreamResponse.Result response = (StreamResponse.Result) streamResponse;
      List<Map<String, Object>> allWeatherForecasts =
        (List<Map<String, Object>>) response.getResult().getData();
      finalizeUI();
    }
  }

  @Override
  public void onError(Throwable throwable) {
    // an error occurred in the function
  }

  @Override
  public void onComplete() {

  }
});
```

### Configure CORS (Cross-Origin Resource Sharing)

Use the `cors` option to control which origins can access your function.

By default, callable functions have CORS configured to allow requests from all
origins. To allow some cross-origin requests, but not all, pass a list of
specific domains or regular expressions that should be allowed. For example:

### Node.js

```javascript
const { onCall } = require("firebase-functions/v2/https");

exports.getGreeting = onCall(
  { cors: [/firebase\.com$/, "https://flutter.com"] },
  (request) => {
    return "Hello, world!";
  }
);
```

### Python

```python
from firebase_functions import https_fn, options

@https_fn.on_call(
    cors=options.CorsOptions(
        cors_origins=[r"firebase\.com$", r"https://flutter\.com"],
        cors_methods=["get", "post"],
    )
)
def say_hello(req: https_fn.CallableRequest) -> Any:
    return "Hello world!"
```

### Dart (experimental)

```dart
import 'package:firebase_functions/firebase_functions.dart';

void main(List<String> args) {
  fireUp(args, (firebase) {
    firebase.https.onCall(
      name: 'getGreeting',
      options: CallableOptions(
        cors: Cors([RegExp(r'^https:\/\/firebase\.com$'), 'https://flutter.com']),
      ),
      (request) async {
        return CallableResult('Hello, world!');
      },
    );
  });
}
```

To forbid cross-origin requests, set the `cors` policy to `false`.

### Handle errors

To ensure the client gets useful error details, return errors from a callable
by throwing (or for Node.js returning a Promise rejected with) an instance of
`functions.https.HttpsError` or `https_fn.HttpsError`.
The error has a `code` attribute that can be one of the values listed in gRPC
[Status codes](https://github.com/grpc/grpc/blob/master/doc/statuscodes.md).
The errors also have a string `message`, which defaults
to an empty string. They can also have an optional `details` field with an
arbitrary value. If an error other than an HTTPS error is thrown from your functions,
your client instead receives an error with the message `INTERNAL` and the code
`internal`.

For example, a function could throw data validation and authentication errors
with error messages to return to the calling client:

### Node.js

```javascript
// Checking attribute.
if (!(typeof text === "string") || text.length === 0) {
  // Throwing an HttpsError so that the client gets the error details.
  throw new HttpsError("invalid-argument", "The function must be called " +
          "with one arguments \"text\" containing the message text to add.");
}
// Checking that the user is authenticated.
if (!request.auth) {
  // Throwing an HttpsError so that the client gets the error details.
  throw new HttpsError("failed-precondition", "The function must be " +
          "called while authenticated.");
}
```

### Python

```python
# Checking attribute.
if not isinstance(text, str) or len(text) < 1:
    # Throwing an HttpsError so that the client gets the error details.
    raise https_fn.HttpsError(
        code=https_fn.FunctionsErrorCode.INVALID_ARGUMENT,
        message=(
            'The function must be called with one argument, "text",'
            " containing the message text to add."
        ),
    )

# Checking that the user is authenticated.
if req.auth is None:
    # Throwing an HttpsError so that the client gets the error details.
    raise https_fn.HttpsError(
        code=https_fn.FunctionsErrorCode.FAILED_PRECONDITION,
        message="The function must be called while authenticated.",
    )
```

### Dart (experimental)

```dart
// Checking that attributes are present and are numbers.
if (firstNumber is! num || secondNumber is! num) {
  // Throwing an HttpsError so that the client gets the error details.
  throw InvalidArgumentError(
    'The function must be called with two arguments "firstNumber" and "secondNumber" which must both be numbers.',
  );
}
```

### Deploy the callable function

After you save a completed callable function within `index.js`, it
is deployed along with all other functions when you run `firebase deploy`.
To deploy only the callable, use the `--only` argument as shown to perform
[partial deploys](https://firebase.google.com/docs/cli.md.txt#partial_deploys):

```
firebase deploy --only functions:addMessage
```

If you encounter permissions errors when deploying functions, make sure that
the appropriate [IAM roles](https://firebase.google.com/docs/projects/iam/permissions.md.txt#functions) are
assigned to the user running the deployment commands.

## Set up your client development environment

Make sure you meet any prerequisites, then add the required dependencies and
client libraries to your app.

### iOS+

Follow the instructions to [add Firebase to your Apple app](https://firebase.google.com/docs/ios/setup.md.txt).

Use Swift Package Manager to install and manage Firebase dependencies.

> [!NOTE]
> Visit [our installation guide](https://firebase.google.com/docs/ios/installation-methods.md.txt) to learn about the different ways you can add Firebase SDKs to your Apple project.

1. In Xcode, with your app project open, navigate to **File \> Add Packages**.
2. When prompted, add the Firebase Apple platforms SDK repository:

```
  https://github.com/firebase/firebase-ios-sdk.git
```

> [!NOTE]
> **Note:** New projects should use the default (latest) SDK version, but you can choose an older version if needed.

3. Choose the Cloud Functions library.
4. Add the `-ObjC` flag to the *Other Linker Flags* section of your target's build settings.
5. When finished, Xcode will automatically begin resolving and downloading your dependencies in the background.

### Web

1. Follow the instructions to [add Firebase to your Web app](https://firebase.google.com/docs/web/setup.md.txt). Make sure to run the following command from your terminal:

   ```
   npm install firebase@13.2.0 --save
   ```
2. Manually require both Firebase core and Cloud Functions:

   ```
    import { initializeApp } from 'firebase/app';
    import { getFunctions } from 'firebase/functions';

    const app = initializeApp({
        projectId: '### CLOUD FUNCTIONS PROJECT ID ###',
        apiKey: '### FIREBASE API KEY ###',
        authDomain: '### FIREBASE AUTH DOMAIN ###',
      });
    const functions = getFunctions(app);
   ```

### Android

1. Follow the instructions to
   [add Firebase to your Android app](https://firebase.google.com/docs/android/setup.md.txt).

2.


   In your **module (app-level) Gradle file**
   (usually `<project>/<app-module>/build.gradle.kts` or
   `<project>/<app-module>/build.gradle`),
   add the dependency for the Cloud Functions library for Android. We recommend using the
   [Firebase Android BoM](https://firebase.google.com/docs/android/learn-more.md.txt#bom)
   to control library versioning.


   ```
   dependencies {
       // Import the BoM for the Firebase platform
       implementation(platform("com.google.firebase:firebase-bom:35.1.0"))

       // Add the dependency for the Cloud Functions library
       // When using the BoM, you don't specify versions in Firebase library dependencies
       implementation("com.google.firebase:firebase-functions")
   }
   ```

   By using the [Firebase Android BoM](https://firebase.google.com/docs/android/learn-more.md.txt#bom),
   your app will always use compatible versions of Firebase Android libraries.
   *(Alternative)*
   Add Firebase library dependencies *without* using the BoM

   If you choose not to use the Firebase BoM, you must specify each Firebase library version
   in its dependency line.

   **Note that if you use *multiple* Firebase libraries in your app, we strongly
   recommend using the BoM to manage library versions, which ensures that all versions are
   compatible.**

   ```groovy
   dependencies {
       // Add the dependency for the Cloud Functions library
       // When NOT using the BoM, you must specify versions in Firebase library dependencies
       implementation("com.google.firebase:firebase-functions:23.0.0")
   }
   ```

   <br />

## Initialize the client SDK

Initialize an instance of Cloud Functions:

### Swift

```swift
lazy var functions = Functions.functions()
```

### Objective-C

```objective-c
@property(strong, nonatomic) FIRFunctions *functions;
// ...
self.functions = [FIRFunctions functions];
```

### Web

    const app = initializeApp({
      projectId: '### CLOUD FUNCTIONS PROJECT ID ###',
      apiKey: '### FIREBASE API KEY ###',
      authDomain: '### FIREBASE AUTH DOMAIN ###',
    });
    const functions = getFunctions(app);

### Kotlin

```kotlin
private lateinit var functions: FirebaseFunctions
// ...
functions = Firebase.functions
```

### Java

```java
private FirebaseFunctions mFunctions;
// ...
mFunctions = FirebaseFunctions.getInstance();
```

> [!NOTE]
> **Note:** To call a function running in any [location](https://firebase.google.com/docs/functions/locations.md.txt) other than `us-central1`, you must set the appropriate value at initialization. For example, on Android you would initialize with `getInstance(FirebaseApp app, String region)`.

## Call the function

### Swift

```swift
functions.httpsCallable("addMessage").call(["text": inputField.text]) { result, error in
  if let error = error as NSError? {
    if error.domain == FunctionsErrorDomain {
      let code = FunctionsErrorCode(rawValue: error.code)
      let message = error.localizedDescription
      let details = error.userInfo[FunctionsErrorDetailsKey]
    }
    // ...
  }
  if let data = result?.data as? [String: Any], let text = data["text"] as? String {
    self.resultField.text = text
  }
}
```

### Objective-C

```objective-c
[[_functions HTTPSCallableWithName:@"addMessage"] callWithObject:@{@"text": _inputField.text}
                                                      completion:^(FIRHTTPSCallableResult * _Nullable result, NSError * _Nullable error) {
  if (error) {
    if ([error.domain isEqual:@"com.firebase.functions"]) {
      FIRFunctionsErrorCode code = error.code;
      NSString *message = error.localizedDescription;
      NSObject *details = error.userInfo[@"details"];
    }
    // ...
  }
  self->_resultField.text = result.data[@"text"];
}];
```

### Web

    var addMessage = firebase.functions().httpsCallable('addMessage');
    addMessage({ text: messageText })
      .then((result) => {
        // Read result of the Cloud Function.
        var sanitizedMessage = result.data.text;
      });

### Web

    import { getFunctions, httpsCallable } from "firebase/functions";

    const functions = getFunctions();
    const addMessage = httpsCallable(functions, 'addMessage');
    addMessage({ text: messageText })
      .then((result) => {
        // Read result of the Cloud Function.
        /** @type {any} */
        const data = result.data;
        const sanitizedMessage = data.text;
      });

### Kotlin

```kotlin
private fun addMessage(text: String): Task<String> {
    // Create the arguments to the callable function.
    val data = hashMapOf(
        "text" to text,
        "push" to true,
    )

    return functions
        .getHttpsCallable("addMessage")
        .call(data)
        .continueWith { task ->
            // This continuation runs on either success or failure, but if the task
            // has failed then result will throw an Exception which will be
            // propagated down.
            val result = task.result?.data as String
            result
        }
}
```

### Java

```java
private Task<String> addMessage(String text) {
    // Create the arguments to the callable function.
    Map<String, Object> data = new HashMap<>();
    data.put("text", text);
    data.put("push", true);

    return mFunctions
            .getHttpsCallable("addMessage")
            .call(data)
            .continueWith(new Continuation<HttpsCallableResult, String>() {
                @Override
                public String then(@NonNull Task<HttpsCallableResult> task) throws Exception {
                    // This continuation runs on either success or failure, but if the task
                    // has failed then getResult() will throw an Exception which will be
                    // propagated down.
                    String result = (String) task.getResult().getData();
                    return result;
                }
            });
}
```

### Dart

```dart
    final result = await FirebaseFunctions.instance.httpsCallable('addMessage').call(
      {
        "text": text,
        "push": true,
      },
    );
    _response = result.data as String;
```

### C++

```c++
firebase::Future<firebase::functions::HttpsCallableResult> AddMessage(
    const std::string& text) {
  // Create the arguments to the callable function.
  firebase::Variant data = firebase::Variant::EmptyMap();
  data.map()["text"] = firebase::Variant(text);
  data.map()["push"] = true;

  // Call the function and add a callback for the result.
  firebase::functions::HttpsCallableReference doSomething =
      functions->GetHttpsCallable("addMessage");
  return doSomething.Call(data);
}
```

### Unity

```c#
private Task<string> addMessage(string text) {
  // Create the arguments to the callable function.
  var data = new Dictionary<string, object>();
  data["text"] = text;
  data["push"] = true;

  // Call the function and extract the operation from the result.
  var function = functions.GetHttpsCallable("addMessage");
  return function.CallAsync(data).ContinueWith((task) => {
    return (string) task.Result.Data;
  });
}
```

> [!NOTE]
> **Note:** Experimental Dart functions cannot be identified by the client SDKs by name. Instead, you must provide the full Cloud Run URL (of the format `https://<function-name>-<random-hash>.<region>.run.app`) using methods such as [`httpsCallableFromURL()`](https://firebase.google.com/docs/reference/js/functions.md.txt#httpscallablefromurl_7af6987). See the [experimental Dart SDK limitations](https://firebase.google.com/docs/functions/start-dart.md.txt#limitations) for more information.

### Handle errors on the client

The client receives an error if the server threw an error or if the
resulting promise was rejected.

If the error returned by the function is of type `function.https.HttpsError`,
then the client receives the error `code`, `message`, and `details` from the
server error. Otherwise, the error contains the message `INTERNAL` and the
code `INTERNAL`. See guidance for how to
[handle errors](https://firebase.google.com/docs/functions/callable.md.txt#handle-errors) in your callable function.

### Swift

```swift
if let error = error as NSError? {
  if error.domain == FunctionsErrorDomain {
    let code = FunctionsErrorCode(rawValue: error.code)
    let message = error.localizedDescription
    let details = error.userInfo[FunctionsErrorDetailsKey]
  }
  // ...
}
```

### Objective-C

```objective-c
if (error) {
  if ([error.domain isEqual:@"com.firebase.functions"]) {
    FIRFunctionsErrorCode code = error.code;
    NSString *message = error.localizedDescription;
    NSObject *details = error.userInfo[@"details"];
  }
  // ...
}
```

### Web

    var addMessage = firebase.functions().httpsCallable('addMessage');
    addMessage({ text: messageText })
      .then((result) => {
        // Read result of the Cloud Function.
        var sanitizedMessage = result.data.text;
      })
      .catch((error) => {
        // Getting the Error details.
        var code = error.code;
        var message = error.message;
        var details = error.details;
        // ...
      });

### Web

    import { getFunctions, httpsCallable } from "firebase/functions";

    const functions = getFunctions();
    const addMessage = httpsCallable(functions, 'addMessage');
    addMessage({ text: messageText })
      .then((result) => {
        // Read result of the Cloud Function.
        /** @type {any} */
        const data = result.data;
        const sanitizedMessage = data.text;
      })
      .catch((error) => {
        // Getting the Error details.
        const code = error.code;
        const message = error.message;
        const details = error.details;
        // ...
      });

### Kotlin

```kotlin
addMessage(inputMessage)
    .addOnCompleteListener { task ->
        if (!task.isSuccessful) {
            val e = task.exception
            if (e is FirebaseFunctionsException) {
                val code = e.code
                val details = e.details
            }
        }
    }
```

### Java

```java
addMessage(inputMessage)
  .addOnCompleteListener(new OnCompleteListener<String>() {
    @Override
    public void onComplete(@NonNull Task<String> task) {
      if (!task.isSuccessful()) {
        Exception e = task.getException();
        if (e instanceof FirebaseFunctionsException) {
          FirebaseFunctionsException ffe = (FirebaseFunctionsException) e;
          FirebaseFunctionsException.Code code = ffe.getCode();
          Object details = ffe.getDetails();
        }
      }
    }
  });
```

### Dart

```dart
try {
  final result =
      await FirebaseFunctions.instance.httpsCallable('addMessage').call();
} on FirebaseFunctionsException catch (error) {
  print(error.code);
  print(error.details);
  print(error.message);
}
```

### C++

```c++
void OnAddMessageCallback(
    const firebase::Future<firebase::functions::HttpsCallableResult>& future) {
  if (future.error() != firebase::functions::kErrorNone) {
    // Function error code, will be kErrorInternal if the failure was not
    // handled properly in the function call.
    auto code = static_cast<firebase::functions::Error>(future.error());

    // Display the error in the UI.
    DisplayError(code, future.error_message());
    return;
  }

  const firebase::functions::HttpsCallableResult* result = future.result();
  firebase::Variant data = result->data();
  // This will assert if the result returned from the function wasn't a string.
  std::string message = data.string_value();
  // Display the result in the UI.
  DisplayResult(message);
}

// ...

// ...
  auto future = AddMessage(message);
  future.OnCompletion(OnAddMessageCallback);
  // ...
```

### Unity

```c#
 addMessage(text).ContinueWith((task) => {
  if (task.IsFaulted) {
    foreach (var inner in task.Exception.InnerExceptions) {
      if (inner is FunctionsException) {
        var e = (FunctionsException) inner;
        // Function error code, will be INTERNAL if the failure
        // was not handled properly in the function call.
        var code = e.ErrorCode;
        var message = e.ErrorMessage;
      }
    }
  } else {
    string result = task.Result;
  }
});
```

### Set a client timeout

By default, the Cloud Functions client SDKs use a 70-second timeout for
callable requests. If a callable function takes longer than 70 seconds to
complete, the client SDK terminates the request with a `DEADLINE_EXCEEDED`
(`deadline-exceeded`) error---even if you configured a longer server-side timeout.

To support long-running callable functions, you must increase the timeout on
**both** the server and the client:

1. Increase the server-side function timeout (see [Set timeout and memory allocation](https://firebase.google.com/docs/functions/manage-functions.md.txt#set-timeout)).
2. Increase the client-side timeout when configuring the callable reference in your app:

### Swift

```swift
let callable = functions.httpsCallable("addMessage")
callable.timeoutInterval = 300  // 300 seconds (default is 70)
let result = try await callable.call(["text": text, "push": true])
```

### Objective-C

```objective-c
FIRHTTPSCallable *callable = [self.functions HTTPSCallableWithName:@"addMessage"];
callable.timeoutInterval = 300;  // 300 seconds (default is 70)
[callable callWithObject:@{@"text": text, @"push": @YES}
              completion:^(FIRHTTPSCallableResult * _Nullable result, NSError * _Nullable error) {
  // ...
}];
```

### Web

```javascript
var addMessage = firebase.functions().httpsCallable('addMessage', {
  timeout: 300000,  // 300 seconds in milliseconds (default is 70000)
});
addMessage({ text: messageText })
  .then((result) => {
    // ...
  });
```

### Web

```javascript
import { getFunctions, httpsCallable } from "firebase/functions";

const functions = getFunctions();
const addMessage = httpsCallable(functions, 'addMessage', {
  timeout: 300000,  // 300 seconds in milliseconds (default is 70000)
});
const result = await addMessage({ text: messageText });
```

### Kotlin

```kotlin
val callable = functions.getHttpsCallable("addMessage")
callable.setTimeout(300L, TimeUnit.SECONDS)
val result = callable.call(data).await()
```

### Java

```java
HttpsCallableReference callable = mFunctions.getHttpsCallable("addMessage");
callable.setTimeout(300L, TimeUnit.SECONDS);
Task<HttpsCallableResult> result = callable.call(data);
```

### Dart

```dart
final callable = FirebaseFunctions.instance.httpsCallable(
  'addMessage',
  options: HttpsCallableOptions(
    timeout: const Duration(seconds: 300),
  ),
);
final result = await callable.call({
  'text': text,
  'push': true,
});
```

## Recommended: Prevent abuse with App Check

Before you launch your app, you should enable [App Check](https://firebase.google.com/docs/app-check/cloud-functions.md.txt)
to help ensure that only your apps can access your callable function endpoints.