An object that mediates between entities and the persistence layer. It offers a standardized API to query and execute commands on a database.

A repository is storage independent, all the queries and commands are delegated to the current adapter.

This architecture has several advantages:

As of the current version, Hanami only supports SQL databases.


When a class inherits from Hanami::Repository, it will receive the following interface:

A collection is a homogenous set of records. It corresponds to a table for a SQL database or to a MongoDB collection.

repository =

book = repository.create(title: "Hanami")
  # => #<Book:0x007f95cbd8b7c0 @attributes={:id=>1, :title=>"Hanami", :created_at=>2016-11-13 16:02:37 UTC, :updated_at=>2016-11-13 16:02:37 UTC}>

book = repository.find(
  # => #<Book:0x007f95cbd5a030 @attributes={:id=>1, :title=>"Hanami", :created_at=>2016-11-13 16:02:37 UTC, :updated_at=>2016-11-13 16:02:37 UTC}>

book = repository.update(, title: "Hanami Book")
  # => #<Book:0x007f95cb243408 @attributes={:id=>1, :title=>"Hanami Book", :created_at=>2016-11-13 16:02:37 UTC, :updated_at=>2016-11-13 16:03:34 UTC}>


  # => nil

Private Queries

All the queries are private. This decision forces developers to define intention revealing API, instead of leaking storage API details outside of a repository.

Look at the following code: 23).order(:published_at).limit(8)

This is bad for a variety of reasons:

There is a better way:

# lib/bookshelf/repositories/book_repository.rb
class BookRepository < Hanami::Repository
  def most_recent_by_author(author, limit: 8)

This is a huge improvement, because:


To have a track of when a record has been created or updated is important when running a project in production.

When creating a new table, if we add the following columns, a repository will take care of keep the values updated.

Hanami::Model.migration do
  up do
    create_table :books do
      # ...
      column :created_at, DateTime
      column :updated_at, DateTime
repository =

book = repository.create(title: "Hanami")

book.created_at # => 2016-11-14 08:20:44 UTC
book.updated_at # => 2016-11-14 08:20:44 UTC

book = repository.update(, title: "Hanami Book")

book.created_at # => 2016-11-14 08:20:44 UTC
book.updated_at # => 2016-11-14 08:22:40 UTC

When a database table has created_at and updated_at timestamps, a repository will automatically update their values.

Timestamps are on UTC timezone.

Legacy Database

By default, a repository performs auto-mapping of corresponding database table and creates an automatic schema for the associated entity.

When working with legacy databases we can resolve the naming mismatch between the table name, the columns, with repositories defaults and entities attributes.

Let's say we have a database table like this:

CREATE TABLE t_operator (
    operator_id integer NOT NULL,
    s_name text

We can setup our repository with the following code:

# lib/bookshelf/repositories/operator_repository.rb
class OperatorRepository < Hanami::Repository
  self.relation = :t_operator

  mapping do
    attribute :id,   from: :operator_id
    attribute :name, from: :s_name

While the entity can stay with the basic setup:

# lib/bookshelf/entities/operator.rb
class Operator < Hanami::Entity

The entity now gets the mapping we defined in the repository:

operator = "Jane") # => "Jane"

The repository can use the same mapped attributes:

operator = "Jane")
  # => #<Operator:0x007f8e43cbcea0 @attributes={:id=>1, :name=>"Jane"}>


Count is a concept not generally available to all the databases. SQL databases have it, but others don't.

You can define a method, if you're using a SQL database:

class BookRepository < Hanami::Repository
  def count

Or you can expose specific conditions:

class BookRepository < Hanami::Repository
  # ...

  def on_sale_count
    books.where(on_sale: true).count

If you want to use raw SQL you can do:

class BookRepository < Hanami::Repository
  # ...

  def old_books_count"SELECT id FROM books WHERE created_at < (NOW() - 1 * interval '1 year')").count

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