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How to build a Kotlin Multiplatform Mobile app with codemagic.yaml

This guide will illustrate all of the necessary steps to successfully build and publish a Kotlin Multiplatform Mobile app with Codemagic. It will cover the basic steps such as build versioning, code signing and publishing.

You can find a complete project showcasing these steps in our Sample projects repository.

Adding the app to Codemagic

The apps you have available on Codemagic are listed on the Applications page. Click Add application to add a new app.

  1. If you have more than one team configured in Codemagic, select the team you wish to add the app to.
  2. Connect the repository where the source code is hosted. Detailed instructions that cover some advanced options are available here.
  3. Select the repository from the list of available repositories. Select the appropriate project type.
  4. Click Finish: Add application

Creating codemagic.yaml

In order to use codemagic.yaml for build configuration on Codemagic, it has to be committed to your repository. The name of the file must be codemagic.yaml and it must be located in the root directory of the repository. Detailed explanation can be found here.

Tip You can find codemagic.yaml examples in Codemagic Sample Projects repository.

If you prefer to write your codemagic.yaml file from scratch, you can start with this minimal configuration.

workflows:
    sample-workflow:
        name: Codemagic Sample Workflow
        max_build_duration: 120
        instance_type: mac_mini_m2

Tip You can have more than one workflow in the same codemagic.yaml file. If you are building for both the Android and iOS, simply enter both workflows as:
workflows:
    android-workflow-id:
        name: Android Sample Workflow
        # .......    
        # .......
        # .......  
    ios-workflow-id:
        name: iOS Sample Workflow
        # ......

Scan for the codemagic.yaml file by selecting a branch to scan and clicking the Check for configuration file button at the top of the page. Note that you can have different configuration files in different branches.

Code signing

All applications have to be digitally signed before they are made available to the public to confirm their author and guarantee that the code has not been altered or corrupted since it was signed.

Generating a keystore

You can create a keystore for signing your release builds with the Java Keytool utility by running the following command:

keytool -genkey -v -keystore codemagic.keystore -storetype JKS \
        -keyalg RSA -keysize 2048 -validity 10000 -alias codemagic

Keytool then prompts you to enter your personal details for creating the certificate, as well as provide passwords for the keystore and the key. It then generates the keystore as a file called codemagic.keystore in the directory you’re in. The key is valid for 10,000 days.

Uploading a keystore

  1. Open your Codemagic Team settings, and go to codemagic.yaml settings > Code signing identities.
  2. Open Android keystores tab.
  3. Upload the keystore file by clicking on Choose a file or by dragging it into the indicated frame.
  4. Enter the Keystore password, Key alias and Key password values as indicated.
  5. Enter the keystore Reference name. This is a unique name used to reference the file in codemagic.yaml
  6. Click the Add keystore button to add the keystore.

For each of the added keystore, its common name, issuer, and expiration date are displayed.

Note: The uploaded keystore cannot be downloaded from Codemagic. It is crucial that you independently store a copy of the keystore file as all subsequent builds released to Google Play should be signed with the same keystore.

However, keep the keystore file private and do not check it into a public repository.

Referencing keystores in codemagic.yaml

To tell Codemagic to fetch the uploaded keystores from the Code signing identities section during the build, list the reference of the uploaded keystore under the android_signing field.

Add the following code to the environment section of your codemagic.yaml file:

workflows:
  android-workflow:
    name: Android Workflow
    # ....
    environment:
      android_signing:
        - keystore_reference

Default environment variables are assigned by Codemagic for the values on the build machine:

  • Keystore path: CM_KEYSTORE_PATH
  • Keystore password: CM_KEYSTORE_PASSWORD
  • Key alias: CM_KEY_ALIAS
  • Key alias password: CM_KEY_PASSWORD

Signing Android apps using Gradle

To sign your Android app, simply modify your androidApp/build.gradle.kts as follows:

...
  android {
      ...
      defaultConfig { ... }
      signingConfigs {
         create("release") {
                storeFile = file(System.getenv()["CM_KEYSTORE_PATH"])
                storePassword = System.getenv()["CM_KEYSTORE_PASSWORD"]
                keyAlias = System.getenv()["CM_KEY_ALIAS"]
                keyPassword = System.getenv()["CM_KEY_PASSWORD"]
          }
      }
      buildTypes {
          release {
              ...
              signingConfig = signingConfigs.getByName("release")
          }
      }
  }
  ...

Creating the App Store Connect API key

Signing iOS applications requires Apple Developer Program membership.

It is recommended to create a dedicated App Store Connect API key for Codemagic in App Store Connect. To do so:

  1. Log in to App Store Connect and navigate to Users and Access > Integrations » App Store Connect API.
  2. Click on the + sign to generate a new API key.
  3. Enter the name for the key and select an access level. We recommend choosing App Manager access rights, read more about Apple Developer Program role permissions here.
  4. Click Generate.
  5. As soon as the key is generated, you can see it added to the list of active keys. Click Download API Key to save the private key for later. Note that the key can only be downloaded once.
Take note of the Issuer ID above the table of active keys as well as the Key ID of the generated key as these will be required when setting up the Apple Developer Portal integration in the Codemagic UI.

Adding the App Store Connect API key to Codemagic

  1. Open your Codemagic Team settings, go to Team integrations > Developer Portal > Manage keys.
  2. Click the Add key button.
  3. Enter the App Store Connect API key name. This is a human readable name for the key that will be used to refer to the key later in application settings.
  4. Enter the Issuer ID and Key ID values.
  5. Click on Choose a .p8 file or drag the file to upload the App Store Connect API key downloaded earlier.
  6. Click Save.

Adding the code signing certificate

Codemagic lets you upload code signing certificates as PKCS#12 archives containing both the certificate and the private key which is needed to use it. When uploading, Codemagic will ask you to provide the certificate password (if the certificate is password-protected) along with a unique Reference name, which can then be used in the codemagic.yaml configuration to fetch the specific file.

  1. Open your Codemagic Team settings, go to codemagic.yaml settings > Code signing identities.
  2. Open iOS certificates tab.
  3. Upload the certificate file by clicking on Choose a .p12 or .pem file or by dragging it into the indicated frame.
  4. Enter the Certificate password and choose a Reference name.
  5. Click Add certificate

If you have added the App Store Connect API key to Codemagic, you can also generate a new Apple Development or Apple Distribution certificate.

  1. Open your Codemagic Team settings, go to codemagic.yaml settings > Code signing identities.
  2. Open iOS certificates tab.
  3. Click Generate certificate.
  4. Provide a Reference name for the certificate.
  5. Choose the Certificate type.
  6. Select the App Store Connect API key to use.
  7. Click Create certificate.

Once the certificate has been created, Codemagic will allow you to download the certificate and provides the password for it.

After downloading, please follow the steps in the Upload certificate tab to upload the certificate to Codemagic.

Note: The certificate can be downloaded only once, right after creating it.

Note: Apple limits the number of Apple Distribution certificates to 3. If you have already reached the maximum number of certificates, the following error will be displayed:

There is a problem with the request entity - You already have a current Distribution certificate or a pending certificate request.

Similar errors can also arise in rarer cases with Apple Development certificates. To resolve the error, either remove some old certificate from the Apple Developer Portal or upload an existing certificate manually.

Existing signing certificates previously generated by Codemagic can be automatically fetched from Apple Developer Portal based on your team’s App Store Connect API key.

Fetching a certificate that was not generated by Codemagic is not possible because each certificate is linked with a private signing key to which Codemagic has no access.

  1. Open your Codemagic Team settings, go to codemagic.yaml settings > Code signing identities.
  2. Open iOS certificates tab.
  3. Click Fetch certificate.
  4. Select a certificate from the Development certificates or Distribution certificates list.
  5. Click Fetch selected.

Adding the provisioning profile

Codemagic allows you to upload a provisioning profile to be used for the application or to fetch a profile from the Apple Developer Portal.

The profile’s type, team, bundle id, and expiration date are displayed for each profile added to Code signing identities. Furthermore, Codemagic will let you know whether a matching code signing certificate is available in Code signing identities (a green checkmark in the Certificate field) or not.

Note: If your app contains app extensions, an additional provisioning profile is required for each extension. Codemagic will use the bundle identifier to find the relevant provisioning profiles. If your bundle identifier is com.example.app, the matching profiles are the ones with com.example.app and com.example.app.* as bundle identifier.

You can upload provisioning profiles with the .mobileprovision extension, providing a unique Reference name is required for each uploaded profile.

  1. Open your Codemagic Team settings, go to codemagic.yaml settings > Code signing identities.
  2. Open iOS provisioning profiles tab.
  3. Upload the provisioning profile file by clicking on Choose a .mobileprovision file or by dragging it into the indicated frame.
  4. Enter the Reference name for the profile.
  5. Click Add profile.

You can automatically fetch the provisioning profiles from the Apple Developer Portal based on your team’s App Store Connect API key. The bundle identifier is listed for every available profile along with it’s name.

The profiles are displayed grouped by category: Development profiles, Ad Hoc profiles, App Store profiles, and Enterprise profiles. For each selected profile, it is necessary to provide a unique Reference name, which can be later used in codemagic.yaml to fetch the profile.

  1. Open your Codemagic Team settings, go to codemagic.yaml settings > Code signing identities.
  2. Open iOS provisioning profiles tab.
  3. Click Fetch profiles
  4. Select the desired profile(s) and enter a Reference name for each one.
  5. Click Download selected. (scroll down if necessary)

Note: When you make essential changes to a provisioning profile, such as modifying the app ID, adding/removing capabilities from the profile identifier, or changing the certificates assigned to that profile, the provisioning profile becomes invalid. In such situations, you need to generate a new provisioning profile with these updates and then re-upload it to Codemagic.

Referencing certificates and profiles in codemagic.yaml

To fetch all uploaded signing files matching a specific distribution type and bundle identifier during the build, define the distribution_type and bundle_identifier fields in your codemagic.yaml configuration. Note that it is necessary to configure both of the fields.

workflows:
  ios-workflow:
    name: iOS Workflow 
    # ....
    environment:
      ios_signing:
        distribution_type: app_store # or: ad_hoc | development | enterprise
        bundle_identifier: com.example.id

Note: If you are publishing to the App Store or you are using TestFlight to distribute your app to test users, set the distribution_type to app_store.

When using a third party app distribution service such as Firebase App Distribution, set the distribution_type to ad_hoc

When defining the bundle identifier com.example.id, Codemagic will fetch any uploaded certificates and profiles matching the extensions as well (e.g. com.example.id.NotificationService).

Using provisioning profiles

To apply the profiles to your project during the build, add the following script before your build scripts:

  scripts:
    # ... your dependencies installation
    
    - name: Set up code signing settings on Xcode project
      script: xcode-project use-profiles
    
    # ... your build commands
See additional configuration options for setting up code signing settings to use given provisioning profiles here

To distribute signed iOS applications solely to internal testers without the need for Apple’s beta review (TestFlight Internal Testing Only):

  
  scripts:  
    # ... your dependencies installation  
    - name: Set up code signing settings on Xcode project  
      script: xcode-project use-profiles   
                --custom-export-options='{"testFlightInternalTestingOnly": true}'  
    # ... your build commands

Note: Builds marked as TestFlight Internal Only will display “internal” next to the build number and can exclusively be added to internal tester groups. They cannot be submitted for external testing or distributed to customers.

Configure scripts to build the app

Add the following scripts to your codemagic.yaml file in order to prepare the build environment and start the actual build process. In this step you can also define the build artifacts you are interested in. These files will be available for download when the build finishes. For more information about artifacts, see here.

  scripts:
    - name: Build Android release
      script: | 
        ./gradlew assembleRelease
  artifacts:
    - androidApp/build/outputs/**/**/*.aab
  environment:
    vars:
      XCODE_WORKSPACE: "YOUR_APP.xcworkspace"
      XCODE_SCHEME: "YOUR_SCHEME"
  scripts:
    - name: Cocoapods installation
        script: | 
          cd $CM_BUILD_DIR/iosApp
          pod install
    - name: Set up code signing settings on Xcode project
      script: | 
        xcode-project use-profiles
    - name: Build ipa for distribution
      script: | 
          cd $CM_BUILD_DIR/iosApp
          xcode-project build-ipa \
            --workspace "$XCODE_WORKSPACE" \
            --scheme "$XCODE_SCHEME"
    artifacts:
      - iosApp/build/ios/ipa/*.ipa

Build versioning

If you are going to publish your app to App Store Connect or Google Play, each uploaded artifact must have a new version satisfying each app store’s requirements. Codemagic allows you to easily automate this process and increment the version numbers for each build. For more information and details, see here.

One very useful method of calculating the code version is to use Codemagic command line tools to get the latest build number from Google Play and increment it by one.

You can find the full sample project with the instructions on alternative ways to perform Android build versioning in our repository.

The prerequisite is a valid Google Cloud Service Account. Please follow these steps:

  1. Go to this guide and complete the steps in the Google Play section.
  2. Skip to the Creating a service account section in the same guide and complete those steps also.
  3. You now have a JSON file with the credentials.
  4. Open Codemagic UI and create a new Environment variable GCLOUD_SERVICE_ACCOUNT_CREDENTIALS.
  5. Paste the content of the downloaded JSON file in the Value field, set the group name (e.g. google_play) and make sure the Secure option is checked.
  1. Add the google_play variable group to the codemagic.yaml
    workflows:
  android-workflow-id:
    # ....
    environment:
      groups:
        - google_play
  2. Modify the build script to calculate the build number and use it as gradlew arguments.
    scripts:
    # ....
  - name: Build Android release
    script: | 
      LATEST_GOOGLE_PLAY_BUILD_NUMBER=$(google-play get-latest-build-number --package-name "$PACKAGE_NAME")
      if [ -z $LATEST_GOOGLE_PLAY_BUILD_NUMBER ]; then
        # fallback in case no build number was found from Google Play.
        # Alternatively, you can `exit 1` to fail the build
        # BUILD_NUMBER is a Codemagic built-in variable tracking the number
        # of times this workflow has been built
          UPDATED_BUILD_NUMBER=$BUILD_NUMBER
      else
          UPDATED_BUILD_NUMBER=$(($LATEST_GOOGLE_PLAY_BUILD_NUMBER + 1))
      fi
      ./gradlew bundleRelease \
          -PversionCode=$UPDATED_BUILD_NUMBER \
          -PversionName=1.0.$UPDATED_BUILD_NUMBER
  3. Modify the androidApp/build.gradle.kts file to get the build number values and apply them:
    val latestGooglePlayBuildNumber = Integer.valueOf(System.getenv("LATEST_GOOGLE_PLAY_BUILD_NUMBER") ?: System.getenv("BUILD_NUMBER") ?: "0")

....
android {
    ....
    defaultConfig {
        ...
        versionCode = latestGooglePlayBuildNumber + 1
        versionName = "1.0.${latestGooglePlayBuildNumber + 1}"

In order to get the latest build number from App Store or TestFlight, you will need the App Store credentials as well as the Application Apple ID. This is an automatically generated ID assigned to your app and it can be found under General > App Information > Apple ID under your application in App Store Connect.

  1. Add the Application Apple ID to the codemagic.yaml as a variable
  2. Add the script to get the latest build number using app-store-connect and configure the new build number using agvtool.
  3. Your codemagic.yaml will look like this:
    workflows:
  ios-workflow:
    name: iOS Workflow
    integrations:
      app_store_connect: <App Store Connect API key name>
    environment:
      vars:
        APP_STORE_APPLE_ID: 1555555551
    scripts:
      - name: Increment build number
        script: | 
          #!/bin/sh
          cd $CM_BUILD_DIR
          LATEST_BUILD_NUMBER=$(app-store-connect get-latest-app-store-build-number "$APP_STORE_APPLE_ID")
          agvtool new-version -all $(($LATEST_BUILD_NUMBER + 1))
      - name: Build ipa for distribution
      script: | 
        # build command

Publishing

Codemagic offers a wide array of options for app publishing and the list of partners and integrations is continuously growing. For the most up-to-date information, check the guides in the Configuration > Publishing section of these docs. To get more details on the publishing options presented in this guide, please check the Email publishing, the Google Play Store publishing and the App Store Connect.

Email publishing

If the build finishes successfully, release notes (if passed), and the generated artifacts will be published to the provided email address(es). If the build fails, an email with a link to build logs will be sent.

If you don’t want to receive an email notification on build success or failure, you can set success to false or failure to false accordingly.

workflows:
  sample-workflow-id:
    environment: 
      # ...
    scripts: 
      # ...
    publishing: 
      email:
        recipients:
          - user_1@example.com
          - user_2@example.com
        notify:
          success: true
          failure: false

Publishing to Google Play and App Store

Publishing apps to Google Play requires you to set up a service account in Google Play Console and save the content of the JSON key file to a secure environment variable as explained above in Android Build Versioning steps 1-5. Configuring Google Play publishing is simple as you only need to provide credentials and choose the desired track. If the app is in draft status, please also include the submit_as_draft: true or promote the app status in Google Play.

react-native-android:
  # ... 
  publishing:
    # ...
    google_play:
      credentials: $GCLOUD_SERVICE_ACCOUNT_CREDENTIALS
      track: internal
      submit_as_draft: true

Codemagic enables you to automatically publish your iOS or macOS app to App Store Connect for beta testing with TestFlight or distributing the app to users via App Store. Codemagic uses the App Store Connect API key for authenticating communication with Apple’s services. You can read more about generating an API key from Apple’s documentation page.

Please note that:

  1. for App Store Connect publishing, the provided key needs to have App Manager permission,
  2. and in order to submit your iOS application to App Store Connect, it must be code signed with a distribution certificate.

The following snippet demonstrates how to authenticate with and upload the IPA to App Store Connect, submit the build to beta tester groups in TestFlight and configure releasing the app to App Store. See additional configuration options for App Store Connect publishing here.

Note: Please note that you will need to create an app record in App Store Connect before you can automate publishing with Codemagic. It is recommended to upload the very first version of the app manually. Suppose you have set up an app record but have not manually uploaded the app’s first version. In that case, manual configuration of the settings must be done on App Store Connect after the build is complete, such as uploading the required screenshots and providing the values for the privacy policy URL and application category.
# Integration section is required to make use of the keys stored in 
# Codemagic UI under Apple Developer Portal integration.
integrations:
  app_store_connect: <App Store Connect API key name>

publishing:
  app_store_connect:
    # Use referenced App Store Connect API key to authenticate binary upload
    auth: integration 

    # Configuration related to TestFlight (optional)

    # Optional boolean, defaults to false. Whether or not to submit the uploaded
    # build to TestFlight beta review. Required for distributing to beta groups.
    # Note: This action is performed during post-processing.
    submit_to_testflight: true 

    # Optional boolean, defaults to false. Set to true to automatically expire 
    # previous build in review or waiting for review in Testflight before
    # submitting a new build to beta review. Expired builds will no longer be available for testers.
    # Note: This action is performed during post-processing.
    expire_build_submitted_for_review: true

    # Specify the names of beta tester groups that will get access to the build 
    # once it has passed beta review.
    beta_groups: 
      - group name 1
      - group name 2
    
    # Configuration related to App Store (optional)

    # Optional boolean, defaults to false. Whether or not to submit the uploaded
    # build to App Store review. Note: This action is performed during post-processing.
    submit_to_app_store: true

    # Optional boolean, defaults to false. Set to true to cancel the previous 
    # submission (if applicable) when submitting a new build to App Store review.
    # This allows automatically submitting a new build for review if a previous submission exists.
    # Note: This action is performed during post-processing.
    cancel_previous_submissions: true
    
    # Optional, defaults to MANUAL. Supported values: MANUAL, AFTER_APPROVAL or SCHEDULED
    release_type: SCHEDULED

    # Optional. Timezone-aware ISO8601 timestamp with hour precision when scheduling
    # the release. This can be only used when release type is set to SCHEDULED.
    # It cannot be set to a date in the past.
    earliest_release_date: 2021-12-01T14:00:00+00:00 
    
    # Optional. The name of the person or entity that owns the exclusive rights
    # to your app, preceded by the year the rights were obtained.
    copyright: 2021 Nevercode Ltd
  
    # Optional boolean. Whether or not to release an App Store version update in phases.
    # With this option turned on, your version update will be released over a 7-day period
    # to a percentage of your users (selected at random by their Apple ID) with automatic
    # updates turned on. Learn more from 
    # https://developer.apple.com/help/app-store-connect/update-your-app/release-a-version-update-in-phases.
    # If not specified, then App Store version default phased release configuration is reused.
    phased_release: true

Conclusion

Having followed all of the above steps, you now have a working codemagic.yaml file that allows you to build, code sign, automatically version and publish your project using Codemagic CI/CD. Save your work, commit the changes to the repository, open the app in the Codemagic UI and start the build to see it in action.

Your final codemagic.yaml file should look something like this:

workflows:
  android-workflow:
    name: KMM Android Workflow
    max_build_duration: 120
    environment:
      android_signing:
        - keystore_reference
      groups:
        - google_play
      vars:
        PACKAGE_NAME: "io.codemagic.kmmsample"
        GOOGLE_PLAY_TRACK: alpha
    scripts:
      - name: Build Android release
        script: | 
          LATEST_GOOGLE_PLAY_BUILD_NUMBER=$(google-play get-latest-build-number --package-name "$PACKAGE_NAME")
          if [ -z $LATEST_GOOGLE_PLAY_BUILD_NUMBER ]; then
            # fallback in case no build number was found from Google Play.
            # Alternatively, you can `exit 1` to fail the build
            # BUILD_NUMBER is a Codemagic built-in variable tracking the number
            # of times this workflow has been built
            UPDATED_BUILD_NUMBER=$BUILD_NUMBER
          else
            UPDATED_BUILD_NUMBER=$(($LATEST_GOOGLE_PLAY_BUILD_NUMBER + 1))
          fi
          ./gradlew bundleRelease \
            -PversionCode=$UPDATED_BUILD_NUMBER \
            -PversionName=1.0.$UPDATED_BUILD_NUMBER
    artifacts:
      - androidApp/build/outputs/**/**/*.aab
    publishing:
      email:
        recipients:
          - user_1@example.com
          - user_2@example.com
        notify:
          success: true
          failure: false
      google_play:
        credentials: $GCLOUD_SERVICE_ACCOUNT_CREDENTIALS
        track: internal
        submit_as_draft: true
workflows:
  ios-workflow:
    name: KMM iOS Workflow
    max_build_duration: 120
    integrations:
      app_store_connect: codemagic
    environment:
      ios_signing:
        distribution_type: app_store
        bundle_identifier: io.codemagic.kmmsample
      vars:
        APP_STORE_APPLE_ID: 1555555551
        XCODE_WORKSPACE: "iosApp.xcodeproj"
        XCODE_SCHEME: "iosApp"
    scripts:
      - name: Cocoapods installation
        script: | 
          cd $CM_BUILD_DIR/iosApp
          pod install
      - name: Set up code signing settings on Xcode project
        script: | 
          xcode-project use-profiles
      - name: Increment build number
        script: | 
          cd $CM_BUILD_DIR/iosApp
          LATEST_BUILD_NUMBER=$(app-store-connect get-latest-app-store-build-number "$APP_STORE_APPLE_ID")
          agvtool new-version -all $(($LATEST_BUILD_NUMBER + 1))
      - name: Build ipa for distribution
        script: | 
          cd $CM_BUILD_DIR/iosApp
          xcode-project build-ipa \
            --workspace "$XCODE_WORKSPACE" \
            --scheme "$XCODE_SCHEME"
    artifacts:
      - iosApp/build/ios/ipa/*.ipa
    publishing:
      email:
        recipients:
          - user_1@example.com
          - user_2@example.com
        notify:
          success: true
          failure: false
      app_store_connect:
        auth: integration

        # Configuration related to TestFlight (optional)
        # Note: This action is performed during post-processing.
        submit_to_testflight: true
        beta_groups: # Specify the names of beta tester groups that will get access to the build once it has passed beta review.
          - group name 1
          - group name 2

        # Configuration related to App Store (optional)
        # Note: This action is performed during post-processing.
        submit_to_app_store: false

Next steps

While this basic workflow configuration is incredibly useful, it is certainly not the end of the road and there are numerous advanced actions that Codemagic can help you with.

We encourage you to investigate Running tests with Codemagic to get you started with testing, as well as additional guides such as the one on running tests on Firebase Test Lab or Registering iOS test devices.

Documentation on using codemagic.yaml teaches you to configure additional options such as changing the instance type on which to build, or configuring builds to be automatically triggered on repository events.