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🧩 Active Record

✅ Overview​

A data-centric style that is extremely intuitive and easy to implement: "1 Table = 1 Class, 1 Row = 1 Instance". Uses the database structure directly as the application model.

✅ Problems Addressed​

Active Record primarily wanted to solve practical challenges such as:

  • Reducing the effort of O/R Mapping (Table ⇄ Object).
  • Automating/Abstracting typical CRUD patterns.
  • Enabling data manipulation as methods of model classes.
  • Developing fast using frameworks.

Especially with the success of ActiveRecord in Rails, it became the de facto standard for rapid development.

✅ Basic Philosophy & Rules​

● Correspondence between Table and Class​

  • Class Name → Table Name
  • Property → Column
  • Instance → Row

● Row-level Operations (Instance Methods)​

  • save
  • update
  • destroy

● Set-level Operations (Class Methods)​

  • find
  • where
  • order

● Aggregation of Lightweight Business Logic​

  • Validation
  • Simple state checks
  • Simple conditional branching

As a result: Data structure, persistence, and simple behaviors are aggregated in 1 class.

✅ Suitable Applications​

Active Record shines in scenarios like:

  • CRUD-centric apps
  • Admin screens
  • Management dashboards
  • Business systems with "simple states" like inventory management
  • Web apps where frontend and DB structure correspond straightforwardly
  • MVP (Minimum Viable Product)

High speed and low learning cost are very significant strengths.

❌ Unsuitable Cases​

Active Record tends to break down in apps like:

  • Domains with complex business rules.
  • When one table has different meanings in multiple contexts.
  • When behaviors (business logic) increase massively.
  • Complex apps integrating with external services or multiple data sources.
  • When invariants and state transitions need strict management.

→ Logic scatters into service layers and controllers, tending to become an Anemic Domain Model.

✅ History (Genealogy / Parent Styles)​

  • Patternized in Fowler's Patterns of Enterprise Application Architecture.
  • Spread globally with Rails' ActiveRecord implementation.
  • Natural evolution of Transaction Script style.
  • Iconic existence of data-centric design.

✅ Related Styles​

✅ Representative Frameworks​

  • Ruby on Rails (ActiveRecord) The most famous implementation of the Active Record pattern. The philosophy of 1 Class = 1 Table, 1 Instance = 1 Row takes shape directly.

  • Laravel (Eloquent ORM) Active Record implementation close to Rails. Optimized for data-centric / rapid development, structural features are similar to Rails.

  • Django (Partially similar) Django ORM leans towards Data Mapper, but for lightweight logic and simple CRUD, it is often used in an Active Record way.

✅ Design Patterns Supporting This Style​

Active Record itself is a Fowler pattern, but internally the following are used auxiliarily.

  • Template Method Unifies persistence processing steps (Validation → Save → Callback).

  • Strategy Used when switching validation or simple business rules.

  • Proxy Appears in lazy loading and association loading.

  • Observer Mechanism to fire hooks (callbacks) upon model changes.

  • Command Used when expressing "single operations" like Transaction Scripts.

✅ Summary​

Active Record can be evaluated as:

  • Very productive and realistic for simple CRUD apps.
  • Does not scale and easily breaks down for complex domains.

Therefore, the most important question is:

Is this app complex enough to exceed the "limits of Active Record"?

If signs of complexity begin to appear, migration to Domain Model, Layered, Hexagonal, etc. should be considered.