Use generated iOS SDKs

Firebase Data Connect client SDKs let you call your server-side queries and mutations directly from a Firebase app. You generate a custom client SDK in parallel as you design the schemas, queries and mutations you deploy to your Data Connect service. Then, you integrate methods from this SDK into your client logic.

As we've mentioned elsewhere, it's important to note that Data Connect queries and mutations are not submitted by client code and executed on the server. Instead, when deployed, Data Connect operations are stored on the server like Cloud Functions. This means you need to deploy corresponding client-side changes to avoid breaking existing users (for example, on older app versions).

That's why Data Connect provides you with a developer environment and tooling that lets you prototype your server-deployed schemas, queries and mutations. It also generates client-side SDKs automatically, while you prototype.

When you've iterated updates to your service and client apps, both server- and client-side updates are ready to deploy.

What is the client development workflow?

If you followed the Get started, you were introduced to the overall development flow for Data Connect. In this guide, you'll find more detailed information about generating Swift SDKs from your schema and working with client queries and mutations.

To summarize, to use generated Swift SDKs in your client apps, you'll follow these prerequisite steps:

1. Add Firebase to your iOS app.

2. To use the generated SDK, configure it as a dependency in Xcode.

   In the Xcode top navigation bar, select File > Add Package Dependencies > Add Local, and choose the folder containing the generated Package.swift.

Then:

1. Develop your app schema.

2. Set up SDK generation:

   • With the Add SDK to app button in our Data Connect VS Code extension
   • By updating your connector.yaml

3. Initialize your client code and import libraries.

4. Implement calls to queries and mutations.

5. Set up and use the Data Connect emulator and iterate.

Generate your Swift SDK

As with most Firebase projects, work on your Firebase Data Connect client code takes place in a local project directory. Both the Data Connect VS Code extension and the Firebase CLI are important local tools for generating and managing client code.

SDK generation options are keyed to several entries in the dataconnect.yaml file generated when you initialized your project.

Initialize SDK generation

connectorId: "movies"
generate:
  swiftSdk:
    outputDir: "../movies-generated"
    package: "Movies"

outputDir specifies where the generated SDK should output to. If not specified, the connector folder is used as the default output directory.

package specifies the name of the package that will be generated. The generator will create a folder with the name of the package, containing Package.swift and generated code.

observablePublisher (optional) specifies the Observable publisher to use in query refs. Possible values are observableMacro (iOS 17+) and observableObject (pre - iOS 17). The default value, if none is specified, is observableMacro.

Update SDKs while prototyping

If you're prototyping interactively with the Data Connect VS Code extension and its Data Connect emulator, SDK source files are automatically generated and updated while you modify .gql files defining schemas, queries and mutations. This can be a useful feature in hot (re)loading workflows.

Alternatively, you can use the CLI to regenerate SDKs whenever .gql files are changed:

firebase dataconnect:sdk:generate --watch

Generate SDKs for integration and for production releases

In some scenarios, such as preparing project sources to submit for CI tests, you can call the Firebase CLI for a batch update.

In these cases, use firebase dataconnect:sdk:generate.

Initialize the Data Connect iOS SDK

Initialize your Data Connect instance using the information you used to set up Data Connect (all available in the Firebase console Data Connect tab).

Getting a connector instance

The code for your connector will be generated by the Data Connect emulator. If your connector name is movies and the package is movies, as specified in connector.yaml, then retrieve the connector object by calling:

let connector = DataConnect.moviesConnector

Implement queries and mutations

With the connector object, you can run queries and mutations as defined in the GraphQL source code. Suppose your connector has these operations defined:

mutation createMovie($title: String!, $releaseYear: Int!, $genre: String!, $rating: Int!) {
  movie_insert(data: {
    title: $title
    releaseYear: $releaseYear
    genre: $genre
    rating: $rating
  })
}

query getMovieByKey($key: Movie_Key!) {
  movie(key: $key) { id title }
}

query listMoviesByGenre($genre: String!) {
  movies(where: {genre: {eq: $genre}}) {
    id
    title
  }
}

You can then create a movie as follows:

let mutationResult = try await connector.createMovieMutation.execute(
  title: "Empire Strikes Back",
  releaseYear: 1980,
  genre: "Sci-Fi",
  rating: 5)

print("Movie ID: \(mutationResult.data.movie_insert.id)")

To retrieve a movie, you will use a query reference. All query refs are Observable publishers. Depending on the configured publisher (see connector.yaml), they either support the @Observable macro (iOS 17+) or implement the ObservableObject protocol. The default, if none is specified, is the @Observable macro supported on iOS 17+.

In a SwiftUI view, you can bind the query results using the published data variable of the query ref and call the query's execute() method to update the data. The data variable will match the shape of data that was defined in your GQL query definition.

All retrieved results comply with the Decodable protocol. If you included the object's primary key in your GQL fetch, the objects are also Identifiable, allowing you to use them in iterators.

struct ListMovieView: View {
    @StateObject private var queryRef = connector.listMoviesByGenreQuery.ref(genre: "Sci-Fi")
    var body: some View {
        VStack {
            Button {
                Task {
                    do {
                        try await refresh()
                    } catch {
                        print("Failed to refresh: \(error)")
                    }
                }
            } label: {
                Text("Refresh")
            }
                // use the query results in a view
            ForEach(queryRef.data?.movies ?? [], id: \.self.id) { movie in
                    Text(movie.title)
                }
            }
    }
    @MainActor
    func refresh() async throws {
        _ = try await queryRef.execute()
    }
}

Queries also support one-shot execution.

let resultData = try await DataConnect.moviesConnector.listMoviesByGenreQuery.execute(genre: "Sci-Fi")

Handle changes to enumeration fields

An app's schema can contain enumerations, which can be accessed by your GraphQL queries.

As an app's design changes, you may add new enum supported values. For example, imagine that later in your application’s lifecycle you decide to add a FULLSCREEN value to the AspectRatio enum.

In the Data Connect workflow, you can use local development tooling to update your queries and SDKs.

However, before you release an updated version of your clients, older deployed clients may break.

Example resilient implementation

The generated SDK forces handling of unknown values as the generated enums contain an _UNKNOWN value, and Swift enforces exhaustive switch statements.

do {
    let result = try await DataConnect.moviesConnector.listMovies.execute()
    if let data = result.data {
        for movie in data.movies {
            switch movie.aspectratio {
                case .ACADEMY: print("academy")
                case .WIDESCREEN: print("widescreen")
                case .ANAMORPHIC: print("anamorphic")
                case ._UNKNOWN(let unknownAspect): print(unknownAspect)
            }
        }
    }
} catch {
    // handle error
}

Prototype and test your iOS application

Instrument clients to use a local emulator

You can use the Data Connect emulator, whether from the Data Connect VS Code extension or from the CLI.

Instrumenting the app to connect to the emulator is the same for both scenarios.

let connector = DataConnect.moviesConnector
// Connect to the emulator on "127.0.0.1:9399"
connector.useEmulator()

// (alternatively) if you're running your emulator on non-default port:
connector.useEmulator(port: 9999)

// Make calls from your app

Data types in Data Connect SDKs

The Data Connect server represents common and custom GraphQL data types. These are represented in the SDK as follows.