Rubycademy

Price: $25

Welcome to MyActiveRecord!

Are you ready to master advanced Ruby concepts by building your own ORM? This mini-project will teach you how to implement a robust version of ActiveRecord::Base and ActiveRecord::Relation from scratch.

Instead of just using ActiveRecord, you'll learn to implement core ORM functionality yourself, giving you a deep understanding of the underlying mechanisms and the confidence to work with any ORM in the future.

By completing this project, you'll gain valuable insights into metaprogramming, query building, and dynamic class delegation that you can apply to any Ruby project.

This project aims to help you practice and reinforce advanced Ruby concepts, including metaprogramming, query building, and dynamic class delegation. It is highly educational because it allows you to deconstruct how ORMs are built, giving you a deeper understanding of Ruby and practical experience in building a gem-like project.

Tools and Concepts We'll Use

SQLite3 Database: We'll use SQLite3 as our in-memory database to store and query data.

Singleton Pattern: The DatabaseConnection class uses the Singleton pattern to ensure only one instance of the database connection is created.

Metaprogramming: Techniques such as method_missing and dynamically defining methods are used to make our ORM flexible and intuitive.

Delegation: We'll use delegation to forward method calls from the model to the Relation object, similar to how ActiveRecord works internally.

Dynamic Class Generation: In initialize_relation_delegate_cache, we dynamically generate new classes to handle relation-specific logic.

SQL Query Construction: The to_sql method in the Relation class constructs SQL queries based on the accumulated conditions and ordering.

Module Mixins: Modules like ClassSpecificRelation are mixed in to add functionality to dynamically generated classes.

Method Chaining: We will create scopes (where, order, etc.) that can be chained together, providing a convenient API for querying data.

Struct: The CurrentScope struct is used to manage the state of the current query scope, similar to how ActiveRecord manages scope internally.

Why MyActiveRecord Is Educationally Beneficial

Understand how ORMs work by building one from scratch, which provides insight into the abstractions ActiveRecord provides and how they work internally.

Practice advanced Ruby metaprogramming concepts like method_missing, delegation, and dynamically defining methods and classes.

Learn to create an object-oriented structure for building a reusable and extendable library, similar to how a production gem like ActiveRecord is organized.

Understand how to dynamically construct SQL queries and use them to interact with a relational database, reinforcing SQL and Ruby integration.

Expected Result

In this project, we will be building an ORM that resembles ActiveRecord. Below is an example of the kind of query you should be able to write and run by the end of the project:

class User < MyActiveRecord::Base
  def self.active
    where(active: 1)
  end

  def self.recent
    order(created_at: :asc)
  end
end

puts User.where(organization: "RubyCademy").active.recent.count
puts User.where(organization: "RubyCademy").active.recent.to_a
      

The above queries interact with an in-memory SQLite database to fetch users that match specific criteria.

Project Structure

my_activerecord/
├── bin/
│   └── my_activerecord.rb
├── lib/
│   ├── my_activerecord/
│   │   ├── base.rb
│   │   ├── relation.rb
│   │   ├── delegation.rb
│   │   └── class_specific_relation.rb
│   │   └── current_scope.rb
│   │   └── database_connection.rb
│   └── my_activerecord.rb
      

What You'll Learn

By completing this mini-project, you'll gain a deep understanding of:

How ActiveRecord works under the hood

Advanced Ruby metaprogramming techniques

How to build a query builder from scratch

How to implement method chaining in Ruby

How to structure a gem-like project

Tools and Concepts We'll Use

SQLite3 Database

Singleton Pattern

Metaprogramming

Delegation

Dynamic Class Generation

SQL Query Construction

Module Mixins

Method Chaining

Struct

Why MyActiveRecord Is Educationally Beneficial

Understand how ORMs work by building one from scratch

Practice advanced Ruby metaprogramming concepts

Learn to create an object-oriented structure for a reusable library

Understand how to dynamically construct SQL queries

Ready to Build Your Own ORM?

Get instant access to this mini-project and start implementing your own ActiveRecord from scratch!