Erbee

Erbee is a simple gem that generates Mermaid-based ER diagrams for your existing Rails or ActiveRecord projects.
You run a single command, get a .md file (in Mermaid format), then convert it to .svg via Docker if you wish.

1. Quick Installation & Setup

  1. Add Erbee to your Gemfile (in your existing project): ruby # Gemfile gem 'erbee'
  2. Install the gem: bash bundle install
  3. Run the CLI (inside your project directory): bash bundle exec erbee User --depth=1
    • This outputs a Mermaid .md file (e.g. er_diagram.md) with your database entities and associations.

2. Converting Mermaid .md to .svg

To view the diagram as an SVG, you can use Docker and the mermaid-cli container:

# Example: Using the minlag/mermaid-cli Docker image
# - Mount the current directory so Mermaid can read/write files
docker run -it --rm \
-v "$PWD":/data \
minlag/mermaid-cli \
-i er_diagram.md -o er_diagram.svg

Now you have er_diagram.svg in your project folder—open it in any browser or image viewer.

3. View the SVG in Your Browser

Depending on your OS, run one of these commands:

  • macOS: bash open er_diagram.svg
  • Linux: bash xdg-open er_diagram.svg

After that, your browser (or default viewer) should display the diagram.