How do I decorate associated models with Draper?

Use `decorates_association` in your decorator class, e.g., `decorates_association :author`, which automatically decorates the associated object with its corresponding decorator. You can customize it with options like `:with` for specific decorators or `:scope` for query adjustments.

Draper vs Rails helpers: which is better for view logic?

Draper is better for complex, object-oriented presentation logic that needs testing and organization, while Rails helpers are sufficient for simple, procedural snippets. Draper avoids helper namespace pollution and makes logic reusable across models via decorator classes.

How to test Draper decorators in isolation with RSpec?

Use `Draper::ViewContext.test_strategy :fast` in your spec helper to strip out Rails dependencies, and include specific helpers if needed. Write specs in `spec/decorators/` and leverage built-in matchers like `be_decorated_with` for assertions.

Can Draper work with pagination gems like Kaminari?

Yes, Draper supports pagination by delegating methods in collection decorators. For Kaminari, delegate `current_page`, `total_pages`, etc., in a custom `PaginatingDecorator` and set it via `collection_decorator_class` in your decorator.

What are the alternatives to Draper for view models in Rails?

Alternatives include ViewComponent for building reusable UI components with templates, or plain POROs (Plain Old Ruby Objects) for lighter solutions. Draper is best when you want to add presentation methods directly to models without changing view templates extensively.

Is Draper still maintained and compatible with latest Rails?

As per the README, Draper is maintained and supports Rails 5.2+ and Ruby 2.4+. Check the GitHub repository for recent updates and issues, as compatibility with newer Rails versions may require monitoring for breaking changes.

Open-Awesome

draper

MITRubyv4.0.6

A decorator/view-model library for Rails applications that adds an object-oriented layer of presentation logic.

GitHub

5.3k stars523 forks0 contributors

What is draper?

Draper is a Ruby gem that adds decorators (view models) to Rails applications. It provides an object-oriented way to handle presentation logic by wrapping models with decorator classes, separating view concerns from business logic. It solves the problem of tangled helper methods and bloated models by organizing presentation code into testable, reusable decorators.

Target Audience

Rails developers who want to clean up their view layer by moving presentation logic out of helpers and models. It's particularly useful for teams building maintainable applications with complex view requirements.

Value Proposition

Developers choose Draper because it replaces procedural Rails helpers with object-oriented decorators, making presentation logic easier to organize, test, and reuse. Its seamless integration with Rails conventions and support for collections and associations makes it a natural fit for Rails applications.

Overview

Decorators/View-Models for Rails Applications

Use Cases

Best For

Moving complex view logic out of Rails helpers into reusable classes
Adding presentation methods to models without polluting ActiveRecord classes
Formatting data for display (dates, names, URLs) in a centralized way
Testing presentation logic in isolation from models and views
Decorating collections and associated objects in Rails applications
Integrating with pagination gems like Kaminari or will_paginate

Not Ideal For

Applications with minimal view logic where Rails helpers are sufficient without added abstraction
Projects using modern frontend frameworks like React or Vue.js that handle presentation entirely on the client side
Teams already using ViewComponent or similar patterns that encapsulate view logic in reusable components
Performance-critical APIs or services where object decoration overhead could impact response times

Pros & Cons

Pros

Object-Oriented Design

Replaces procedural Rails helpers with decorator classes, making view logic more organized and testable, as demonstrated by moving methods like `publication_status` out of global helpers.

Seamless Rails Integration

Works tightly with ActiveRecord, supporting decoration of collections, associations, and pagination gems like Kaminari, reducing boilerplate in controllers and views.

Built-in Testing Support

Includes matchers for RSpec, MiniTest, and Test::Unit, such as `be_decorated`, allowing easy verification of decorated objects in controller specs.

Flexible Delegation

Offers `delegate_all` for full method access or selective delegation to control which model methods are exposed, enhancing clarity and security in views.

Cons

Abstraction Overhead

Introduces an extra layer of decorator classes that developers must manage, increasing complexity and learning curve, especially for teams new to the pattern.

Performance Trade-offs

Decorator instantiation for each model object can lead to higher memory usage and slower performance, particularly with large collections or high-throughput applications.

Rails-Centric Limitations

Tightly coupled with Rails conventions and ActiveRecord, making it less suitable for non-Rails projects or those using alternative ORMs without additional configuration, as noted with Mongoid support.

Maintenance Burden

As applications scale, managing numerous decorator classes can become cumbersome, risking code duplication or bloated decorators if not carefully disciplined.

Frequently Asked Questions

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