The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.

Hanami Workflow

Tool Grid

Slices Architecture

Hanami applications MUST be organized into isolated slices (slices/admin/, slices/api/, slices/main/).

• Each slice MUST have its own container and dependencies
• Slices SHOULD NOT directly depend on other slices
• Cross-slice communication SHOULD use explicit interfaces or events
• Shared code MUST live in lib/ or app/ (application layer)

# slices/admin/config/slice.rb
module Admin
  class Slice < Hanami::Slice
    import keys: ["persistence.rom"], from: :main
  end
end

Dependency Injection via Deps

Hanami uses dry-system for dependency injection. All dependencies MUST be injected, not hardcoded.

module Main::Actions::Books
  class Show < Main::Action
    include Deps["repositories.book_repository"]

    def handle(request, response)
      book = book_repository.find(request.params[:id])
      response.body = book.to_json
    end
  end
end

• MUST use include Deps[...] for injecting dependencies
• SHOULD prefer constructor injection for testability
• MUST NOT use global state or singletons directly

Entities, Relations, and Repositories (ROM)

Hanami uses ROM (Ruby Object Mapper) for persistence.

Entities

Entities MUST be simple domain objects without persistence logic.

module MyApp::Entities
  class Book < Hanami::Entity
    attribute :id, Types::Integer
    attribute :title, Types::String
  end
end

Relations

Relations MUST define the database schema mapping.

module MyApp::Relations
  class Books < Hanami::DB::Relation
    schema :books, infer: true do
      associations { belongs_to :author; has_many :reviews }
    end
  end
end

Repositories

Repositories MUST encapsulate all persistence operations.

module MyApp::Repositories
  class BookRepository < Hanami::DB::Repo
    def find(id) = books.by_pk(id).one
    def published = books.where { published_at <= Date.today }.to_a
    def create(attrs) = books.changeset(:create, attrs).commit
  end
end

• Repositories MUST NOT expose ROM internals to actions
• Relations SHOULD use infer: true when schema matches database
• Changesets SHOULD be used for create/update operations

Validation with dry-validation

Input validation MUST use dry-validation contracts.

module Main::Contracts::Books
  class Create < Hanami::Action::Contract
    params do
      required(:title).filled(:string, min_size?: 1)
      required(:author).filled(:string)
      optional(:published_at).maybe(:date)
    end

    rule(:title) do
      key.failure("must be unique") if BookRepository.new.exists?(title: value)
    end
  end
end

• Contracts MUST validate all external input
• Params SHOULD define type coercion
• Error messages MUST be user-friendly

Actions

Actions MUST be single-purpose request handlers.

module Main::Actions::Books
  class Create < Main::Action
    include Deps["repositories.book_repository"]
    contract Contracts::Books::Create

    def handle(request, response)
      result = request.params
      if result.valid?
        book = book_repository.create(result.to_h)
        response.status = 201
        response.body = book.to_json
      else
        response.status = 422
        response.body = { errors: result.errors.to_h }.to_json
      end
    end
  end
end

• Each action MUST handle exactly one request type
• Actions MUST use contracts for input validation
• Actions SHOULD delegate business logic to interactors/services

Views and Templates

Views MUST separate presentation logic from templates.

module Main::Views::Books
  class Show < Main::View
    expose :book do |book:|
      BookPresenter.new(book)
    end
  end
end

<%# slices/main/templates/books/show.html.erb %>
<article>
  <h1><%= book.title %></h1>
  <p>By <%= book.author %></p>
</article>

• Views MUST use expose for passing data to templates
• Templates SHOULD contain minimal logic
• Presenters SHOULD format data for display

Configuration

# config/app.rb
module MyApp
  class App < Hanami::App
    config.actions.content_security_policy[:script_src] = "'self'"
    config.logger.level = :info
  end
end

# slices/api/config/slice.rb
module Api
  class Slice < Hanami::Slice
    config.actions.format :json
    config.actions.default_response_format = :json
  end
end

• Sensitive config MUST use environment variables
• Per-slice config SHOULD override app defaults only when needed

Testing Patterns

# Action test - mock dependencies
RSpec.describe Main::Actions::Books::Show do
  subject(:action) { described_class.new(book_repository: repository) }
  let(:repository) { instance_double(BookRepository) }

  it "returns book" do
    allow(repository).to receive(:find).with(1).and_return(Book.new(id: 1))
    expect(action.call(id: 1).status).to eq(200)
  end
end

# Repository test - real database
RSpec.describe BookRepository, type: :database do
  it "finds published" do
    subject.create(title: "Old", published_at: Date.today - 30)
    expect(subject.published.map(&:title)).to eq(["Old"])
  end
end

• Actions MUST be tested with mocked dependencies
• Repositories SHOULD be tested against real database

Interactor/Service Pattern

module MyApp::Interactors::Books
  class Publish
    include Deps["repositories.book_repository", "events.publisher"]

    def call(book_id)
      book = book_repository.find(book_id) or return Failure(:not_found)
      updated = book_repository.update(book_id, published_at: Date.today)
      publisher.publish("book.published", book_id: book_id)
      Success(updated)
    end
  end
end

• Services SHOULD return Result objects (Success/Failure)
• Actions SHOULD use halt for error responses