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Convention over Configuration

Rails' core philosophy — convention trumps configuration

Convention over Configuration (CoC) is Rails' most important philosophy. Instead of configuring everything manually, follow Rails' conventions and everything connects automatically.

Key Conventions:

  • Model name Post → table name posts (plural, snake_case)

  • Controller PostsController → file app/controllers/posts_controller.rb

  • View PostsController#show → app/views/posts/show.html.erb

  • Foreign key user_id → belongs_to :user

  • Primary key is always id, auto-generated fields are created_at, updated_at

In frameworks like Java/Spring, you need to map everything with XML or annotations, but in Rails, just follow naming conventions. This allows you to focus on feature development immediately without spending time on configuration.

However, without knowing the conventions it can feel like "magic" and debugging becomes difficult, so understanding the conventions precisely is important.

Key Points

1

rails generate model Post title:string content:text → Post model + posts migration auto-generated

2

rails generate controller Posts index show → PostsController + view files auto-generated

3

resources :posts — one line generates 7 RESTful routes

4

Post.find(1) → SELECT * FROM posts WHERE id = 1 auto-conversion (table name convention)

5

Omitting render auto-renders view matching action name (show → show.html.erb)

6

Explicit config only when deviating from conventions (self.table_name = "my_posts")

Pros

  • ✓ Saves significant initial setup time
  • ✓ Automatic code consistency
  • ✓ File location reveals its role
  • ✓ Entire ecosystem uses the same conventions

Cons

  • ✗ Feels like "magic" without knowing conventions
  • ✗ Deviating from conventions can increase complexity
  • ✗ Initially confusing for devs from other frameworks
  • ✗ Implicit behavior can make debugging harder

Use Cases

Minimize initial project setup Maintain code consistency across teams Predictable patterns during code review Faster onboarding for new team members

Related

🏗️
MVC Pattern
Model-View-Controller — The core architecture of Rails
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