Hello World On MacOS

This document describes how to get started with continuous integration on macOS build environments on CircleCI. If you still need to get acquainted with CircleCI, it is recommended to checkout the getting started guide.

Also, there is documentation for testing iOS and an example iOS project.

Prerequisites

To follow along with this document you will need:

• An account on CircleCI.
• A subscription to a paid plan to enable building on the macOS executor.
• An Apple computer with XCode installed on it (if you want to open the example project).

Overview of the macOS executor

The macOS build environment (or executor) is used for iOS and macOS development, allowing you to test, build, and deploy macOS and iOS applications on CircleCI. The macOS executor runs jobs in a macOS environment and provides access to iPhone, iPad, Apple Watch and Apple TV simulators.

Before we get to setting up the macOS executor, we will need to setup our example application.

Example application

The example application is a simple mac app - it runs a 5 minute timer and contains a single unit test (real-world applications will be far more complex; this app simply serves as an introduction to the macOS build environment).

As a user getting to know the macOS build environment, our ideal scenario is for CircleCI to help with the following:

• Run tests using XCode on the macOS VM whenever we push code.
• Create and upload the compiled application as an artifact after tests have run successfully.

You can checkout the example application’s repo on GitHub.

Example configuration file

Our application does not make use of any external tools or dependencies, so we have a fairly simple .circleci/config.yml file. Below, each line is commented to indicate what is happening at each step.

version: 2.1
jobs: # a basic unit of work in a run
  build: # runs not using `Workflows` must have a `build` job as entry point
    macos:  # indicate that we are using the macOS executor
      xcode: 11.3.0 # indicate our selected version of Xcode
    steps: # a series of commands to run
      - checkout  # pull down code from your version control system.
      - run:
          # run our tests using xcode's cli tool `xcodebuild`
          name: Run Unit Tests
          command: xcodebuild test -scheme circleci-demo-macos
      - run:
          # build our application
          name: Build Application
          command: xcodebuild
      - run:
          # compress Xcode's build output so that it can be stored as an artifact
          name: Compress app for storage
          command: zip -r app.zip build/Release/circleci-demo-macos.app
      - store_artifacts: # store this build output. Read more: https://circleci.com/docs/2.0/artifacts/
          path: app.zip
          destination: app

If this is your first exposure to a CircleCI config.yml, some of the above might seem a bit confusing. In the section below you can find some links that provide a more in-depth overview of how a config.yml works.

Since this is a general introduction to building on MacOs, the config.yml above example covers the following:

• Picking an executor to use
• Pulling code via the checkout key
• Running tests with Xcode
• Building our application
• Compressing our application and storing it with the store_artifacts key.

You can learn more about the config.yml file in the configuration reference guide.

Xcode Cross Compilation

Universal Binaries

Xcode currently supports the creation of universal binaries which can be run on both x86_64 and ARM64 CPU architectures without needing to ship separate executables. This is supported only under Xcode 12.2+ although older Xcode versions can still be used to compile separate x86_64 and ARM64 executables.

Extracting Unwanted Architectures

Xcode 12.2+ will by default create universal binaries, compiling to a single executable that supports both x86_64 and ARM64 based CPUs. If you need to remove an instruction set, you can do so by using the lipo utility.

Assuming that we are interested in creating a standalone x86_64 binary from a universal binary called circleci-demo-macos, we can do so by running the command

lipo -extract x86_64 circleci-demo-macos.app/Contents/MacOS/circleci-demo-macos -output circleci-demo-macos-x86_64

We can then confirm the supported architecture of the extracted binary with lipo -info circleci-demo-macos-x86_64 which will output the following

Architectures in the fat file: circleci-demo-macos-x86_64 are: x86_64

Cross Compiled Binaries

While universal binaries are only supported under Xcode 12.2+, you can still cross compile binaries for architectures other than the architecture of the machine being used to build the binary. For xcodebuild the process is relatively straightforward. To build ARM64 binaries, prepend the xcodebuild command with ARCHS=ARM64 ONLY_ACTIVE_ARCH=NO such that it reads xcodebuild ARCHS=ARM64 ONLY_ACTIVE_ARCH=NO .... For the x86_64 architecture simply change ARCHS to x86_64.

Next steps

The macOS executor is commonly used for testing and building iOS applications, which can be more complex in their continuous integrations configuration. If you are interested in building and/or testing iOS applications, consider checking out our following docs that further explore this topic:

• Testing iOS Applications on macOS
• iOS Project Tutorial
• Setting Up Code Signing for iOS Projects

Also, consider reading documentation on some of CircleCI’s features:

• See the Concepts document for a summary of 2.0 configuration and the hierarchy of top-level keys in a .circleci/config.yml file.

• Refer to the Workflows document for examples of orchestrating job runs with concurrent, sequential, scheduled, and manual approval workflows.

• Find complete reference information for all keys and pre-built Docker images in the Configuring CircleCI and CircleCI Images documentation, respectively.