Running BackendKit (Firebase Functions) Locally

BackendKit (SwiftyLaunch Module) - Running BackendKit Locally

Of course you can always straight up deploy your functions to the cloud and then call them from your front.

But what if your app is already live and you don't want to mess up your backend while you're developing new features? Or don't want to wait up to a couple of minutes for your changes to be live?

That's why we recommend to run your backend locally, while you're developing for it. It's also pretty straight forward after initial setup.

Setup

Make sure you have the Firebase CLI installed

We already cover this in the BackendKit Setup, but in case you don't have it installed yet, you can do so by running:

npm install -g firebase-tools

Set up admin credentials

To use Auth and other sensitive Firebase services locally, you need to set up admin credentials.

Get Service Account Key

Go to your Service Account Panel (opens in a new tab) and select your Firebase project. (In case you don't have one yet, DO THE INITIAL SETUP FIRST!)

Service Account Panel

Select the Service account with the name App Engine default service account, press on the three dots and select Manage Keys.

Service Account Manage Keys

Press on Add Key > Create New Key.

Service Account Create Key

Select JSON and press on Create. This will download a JSON file with your credentials.

Service Account JSON Key

Place the key next to your firebase.json file in your Backend Folder (projectpath/Backend/firebase-func/drop-it-here)

Service Account JSON Key Save Location

Set your Google default credentials to point to the downloaded key. First, copy the path of the key file, then paste it into the terminal and run:

export GOOGLE_APPLICATION_CREDENTIALS="path/to/key.json"

Set up Cloud Functions Emulator

Go to your /firebase-func folder and run:

firebase init emulators

In the setup, select the following:

Select your Google Account that is connected to your current Firebase project.
Select Functions Emulator, Firestore Emulator and Authentication Emulator
Keep pressing enter to select the default options.

Set up your App to use the Local Backend

In your app, go to your functions definition in FirebaseBackend.swift, run .useEmulator() after declaration. Use the DEBUG flag so it will only be included in development builds of your app.

FirebaseBackend.swift

import FirebaseFunctions
// ...
public class DB: ObservableObject {
    // ...
	let functions: Functions
    // ...
    init() {
        functions = Functions.functions()
        #if DEBUG
        functions.useEmulator(withHost: "127.0.0.1", port: 5001)
        #endif
        // ...
    }
    // ...
}
// ....

Running the Emulator

From your /firebase-func folder, run:

firebase emulators:start

Now, if everything went smoothly, you will see a following output in your terminal, telling about the relevant emulator URLs:

Firebase Emulator Successfully Running

Go to http://localhost:4000 and see the Firebase Emulator Suite.

Firebase Emulator Suite

You can now test your functions locally, without affecting your live backend. (Things like the Firestore Database will also work locally!)

Local changes are also reflected immediately, so you can test your changes right away. Click here to see how to deploy your changes to the cloud.

Using BackendKit AnalyticsKit Integration