The document discusses setting up continuous integration and continuous delivery (CI/CD) pipelines for mobile applications using React Native. It describes initially using Expo for rapid development but then shifting to core React Native for more control. The pipelines are built using Fastlane to automate builds and deployments, a GitLab runner on a Mac mini to build iOS apps, and Firebase for distribution. Android builds take about 8 minutes while iOS builds take around 20 minutes on average.

1. Building CI / CD for Mobile
Development
● Nihal Shrestha

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CI/CD
Continuous integration (CI) and continuous delivery
(CD) embody a culture, set of operating principles,
and collection of practices that enable application
development teams to deliver code changes more
frequently and reliably.

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Mobile Tech Stack
React Native
React Native is a JavaScript framework
for writing real, natively rendering
mobile applications for iOS and
Android.
Two ways we can start building mobile
apps using React Native:
● Expo [Previously Used]
● Core React Native [Currently using]

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Expo is a set of tools built and a wrapper around React Native.
● No need to setup tedious environment setup like Android Studio and Xcode.
● No need to have Mac for iOS development.
● Able to start building apps within a couple of minutes.
● Provides their own servers for building both Android and iOS apps. [Pipeline]
Limitations (Why we needed to shift to Core RN):
● Less control over both platforms.
● Limited number of native features inbuilt within expo. [like bluetooth services]
● Similarly, integrating with third parties native libraries that are not yet
supported by expo. [Esewa SDK, Khalti SDK]
● Larger build sizes.
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Expo
Journey from Expo to Core RN
Fig 1: Expo
Fig 2: React Native

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Expo provided us their own build server, where we used to build our apps
[Android & iOS]. The process of building and deploying was fairly easy and
faster.
But,
As we shifted to Core RN, each build became dependent upon dev’s local
machine. So, as the project moved ahead, developer had to build and
deploy every new release from their own system and, also the whole
development team became dependent upon it.
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So, Why we didn’t need CI/CD previously and Why do
we need it now?

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One key point to be noted before diving into the detailed
explanation of CI/CD:
● iOS apps can only be build on macOS system. i.e, We
somehow needed to make our CI system around a macOS
computer.
○ Meaning, We will be using an iMac as a build server for both Android and iOS.
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General Flow Diagram

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● Fastlane:
○ Fastlane is the easiest way to automate deployments and releases for your iOS and
Android apps. It handles all tedious tasks, like dealing with code signing, and releasing
your application.
○ All we have to do is configure a Fastfile that defines the steps needed to build and deploy
your mobile application.
○ Fastfile is written in ruby.
● Gitlab Runner:
○ GitLab Runner is an application that works with GitLab CI/CD
to run jobs in a pipeline.
○ A GitLab runner clones the project, reads the gitlab-ci.yml file
and do what it is instructed to do.
○ In our case, Gitlab runner is installed and used in
macOS(iMac).
[Supported OS: Linux, Windows, macOS]
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● Firebase App Distribution:
Firebase App Distribution makes distributing your apps to trusted testers and teammates
painless. By getting your apps onto testers' devices quickly, you can get feedback early and
often.
Steps:
- Upload your latest pre-release build
- Invite testers
- Get feedback
- Release new beta builds
Firebase app distribution is fully supported with Fastlane. So, all of the task can be
automated using Fastlane ( from uploading the build files to sending an invitations ).
● Detailed Architectural Diagram for each platform:
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● Main Steps to follow for Android (One time setup):
○ Fastfile configuration. Set of instructions for running build.
○ Certificate generation. (Keystore using keytool)
■ Key store password
■ Key alias
■ Key password
○ Generating firebase token.
All of these keys needs to be configured as an ENV variable in Gitlab CI which will be
used during build process.
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● Main Steps to follow for iOS (One time setup):
○ Fastfile configuration. Set of instructions for running build.
○ Certificate generation using MATCH.
■ Type
■ App identifier
■ Keychain password
■ Team id
■ Profile name
○ Generating firebase token.
All of these keys needs to be configured as an ENV variable in Gitlab CI which will be
used during build process.
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Results
We are currently achieving the following build time(avg):
1. Android: ~ 8 min
2. iOS: ~ 20 min
Note: Build time may vary according to the project requirements.

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Different Mobile CI available in the market
1. Android: ~ 7 min [Gurzu]
2. iOS: ~ 20 min [Gurzu]

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Special thanks to:
● Avash Mulmi
● Sanjeev Tamang
● Aman Maharjan

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Thank You