basic_workflow.yml

# The name showed in the GitHub Actions tab.
name: Basic workflow

# When the workflow should run. You can have multiple events.
on: # Events can be related to repository, time, manual trigger, other.
  #push: # You can limit the event to changes in specific files using "paths".
  #  branches: [ master ] # You use regex like release/*.
  workflow_dispatch: # Manual trigger with no option.

# The jobs of the workflow, that runs in parallel by default.
jobs:
  # The ID of the 1st job. Here to find all library/ sub-directories.
  discover:
    # The name of the job showed in GitHub Actions tab.
    name: Discover Libraries
    # The OS to run the job on.
    runs-on: ubuntu-latest # Images removed often: 20.04 already unavailable.
    # This job creates an output other jobs can use.
    outputs:
      # Here, "patterns" is the name of the variable that stores the job output. 
      patterns: ${{ steps.matrix.outputs.patterns }} # Value from step "matrix".
    # Each job has a sequence of sequential steps.
    steps:
      # Execute an official GitHub action stored in the homonymous repository.
      - name: "Checkout code"
        uses: actions/checkout@v4 # Check out the code, so usually done first.
      # Finally find all the library sub-directories.
      - name: "Build the strategy matrix"
        id: matrix
        # What will be done:
        # - from GoF/behavioral/, find directories called "library";
        # - from their paths, removes the prefix "GoF/behavioral/";
        # - ... then also the suffix "library" (so keep only the pattern name);
        # - create a json array like ["pattern1", "pattern2", ...].
        # Finally, make that json the output of this job.
        run: | # Pipe is used when multiple lines to run.
          patterns=$(find GoF/behavioral/ -maxdepth 2 -name "library" -type d | sed 's|GoF/behavioral/||' | sed 's|/library||' | jq -R -s -c 'split("\n")[:-1]')
          echo "patterns=$patterns" >> $GITHUB_OUTPUT

  # Second job.
  build:
    # Execute it after the "discover" job, not in parallel as by default.
    needs: discover
    runs-on: ubuntu-latest
    # Strategy allows to define different configurations to run in parallel.
    strategy:
      # Here the matrix of configurations is the array coming from previosu job.
      matrix:
        # ${{ }} GitHub expression; ${ } shell expresion.
        pattern: ${{ fromJson(needs.discover.outputs.patterns) }}
    steps:
      # Example of step without name or id (they are not mandatory).
      - uses: actions/checkout@v4
      - name: Install GTest from source
        run: |
          git clone https://github.com/google/googletest.git
          cd googletest
          mkdir build && cd build
          cmake .. -DBUILD_GMOCK=ON
          make -j$(nproc)
          sudo make install
      # The steps that do the work. New shell, so no need to "cd ..".
      - name: Create build directory
        run: mkdir -p GoF/behavioral/${{ matrix.pattern }}/library/build/
      - name: Configure CMake
        run: cmake -S GoF/behavioral/${{ matrix.pattern }}/library/ -B GoF/behavioral/${{ matrix.pattern }}/library/build/
      - name: Build project
        run: cmake --build GoF/behavioral/${{ matrix.pattern }}/library/build/