---
title: Keep classes under 100 lines
impact: MEDIUM
impactDescription: Maintain single responsibility and improve maintainability.
tags: ruby, quality, design, architecture
---

## Keep classes under 100 lines

Maintain single responsibility and improve maintainability. Limit classes to 100 lines of code (excluding blank lines and comments). Extract responsibilities into separate classes or modules if a class grows too large.

**Incorrect:**

```ruby
class BigManager
  # 200 lines of mixed logic
end
```

**Correct:**

```ruby
class OrderProcessor
  # focused logic < 100 lines
end

class OrderNotifier
  # focused logic < 100 lines
end
```

**Tools:** RuboCop (`Metrics/ClassLength`)