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steveklabnik committed Dec 31, 2012
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+# Contributing to Draper
+
+So you want to help us out... thanks! Here's a quick how-to:
+
+1. [Fork the project](https://help.github.com/articles/fork-a-repo).
+2. Create a branch - `git checkout -b adding_magic`
+3. Make your changes, and add some tests!
+4. Check that the tests pass - `bundle exec rake`
+5. Commit your changes - `git commit -am "Added some magic"`
+6. Push the branch to Github - `git push origin adding_magic`
+7. Send us a [pull request](https://help.github.com/articles/using-pull-requests)!
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+(The MIT License)
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the ‘Software’), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED ‘AS IS’, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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+# Draper: View Models for Rails
+
+[![TravisCI Build Status](https://secure.travis-ci.org/drapergem/draper.png?branch=master)](http://travis-ci.org/drapergem/draper)
+[![Code Climate](https://codeclimate.com/badge.png)](https://codeclimate.com/github/drapergem/draper)
+
+Draper adds a nicely-separated object-oriented layer of presentation logic to your Rails apps. Previously, this logic might have been tangled up in procedural helpers, or contributing to your fat models' weight problems. Now, you can wrap your models up in decorators to organise - and test - this layer of your app much more effectively.
+
+
+## Overview
+
+With Draper, your `Article` model has a corresponding `ArticleDecorator`. The decorator wraps the model, and deals only with presentational concerns. In the controller, you simply decorate your article before handing it off to the view.
+
+```ruby
+# app/controllers/articles_controller.rb
+def show
+ @article = Article.find(params[:id]).decorate
+end
+```
+
+In the view, you can use the decorator in exactly the same way as you would have used the model. The difference is, any time you find yourself needing to write a helper, you can implement a method on the decorator instead. For example, this helper:
+
+```ruby
+# app/helpers/articles_helper.rb
+def publication_status(article)
+ if article.published?
+ "Published at #{article.published_at.strftime('%A, %B %e')}"
+ else
+ "Unpublished"
+ end
+end
+```
+
+could be better written as:
+
+```ruby
+# app/decorators/article_decorator.rb
+class ArticleDecorator < Draper::Decorator
+ def publication_status
+ if published?
+ "Published at #{published_at}"
+ else
+ "Unpublished"
+ end
+ end
+
+ def published_at
+ source.published_at.strftime("%A, %B %e")
+ end
+end
+```
+
+Notice that the `published?` method can be called even though `ArticleDecorator` doesn't define it - the decorator delegates methods to the source model. However, we can override methods like `published_at` to add presentation-specific formatting, in which case we access the underlying model using the `source` method.
+
+You might have heard this sort of decorator called a "presenter", an "exhibit", a "view model", or even just a "view" (in that nomenclature, what Rails calls "views" are actually "templates"). Whatever you call it, it's a great way to replace procedural helpers like the one above with "real" object-oriented programming.
+
+Decorators are the ideal place to:
+* format dates and times using `strftime`,
+* define commonly-used representations of an object, like a `name` method that combines `first_name` and `last_name` attributes,
+* mark up attributes with a little semantic HTML, like turning a `url` field into a hyperlink.
+
+
+## Installation
+
+Add Draper to your Gemfile:
+
+```ruby
+gem 'draper', '~> 1.0'
+```
+
+And run `bundle install` within your app's directory.
+
+
+## Writing decorators
+
+Decorators inherit from `Draper::Decorator`, live in your `app/decorators` directory, and are named for the model that they decorate:
+
+```ruby
+# app/decorators/article_decorator.rb
+class ArticleDecorator < Draper::Decorator
+# ...
+end
+```
+
+### Generators
+
+When you generate a resource with `rails generate resource Article`, you get a decorator for free! But if the `Article` model already exists, you can run `rails generate decorator Article` to create the `ArticleDecorator`.
+
+### Accessing helpers
+
+Procedural helpers are still useful for generic tasks like generating HTML, and as such you can access all this goodness (both built-in Rails helpers, and your own) through the `helpers` method:
+
+```ruby
+class ArticleDecorator < Draper::Decorator
+ def emphatic
+ helpers.content_tag(:strong, "Awesome")
+ end
+end
+```
+
+To save your typing fingers it's aliased to `h`. If that's still too much effort, just pop `include Draper::LazyHelpers` at the top of your decorator class - you'll mix in a bazillion methods and never have to type `h.` again... [if that's your sort of thing](https://github.com/garybernhardt/base).
+
+### Accessing the model
+
+Decorators will delegate methods to the model where possible, which means in most cases you can replace a model with a decorator and your view won't notice the difference. When you need to get your hands on the underlying model the `source` method is your friend (and its aliases `model` and `to_source`):
+
+```ruby
+class ArticleDecorator < Draper::Decorator
+ def published_at
+ source.published_at.strftime("%A, %B %e")
+ end
+end
+```
+
+
+## Decorating
+
+### Single objects
+
+Ok, so you've written a sweet decorator, now you're going to want to put it in action! A simple option is to call the `decorate` method on your model:
+
+```ruby
+@article = Article.first.decorate
+```
+
+This infers the decorator from the object being decorated. If you want more control - say you want to decorate a `Widget` with a more general `ProductDecorator` - then you can instantiate a decorator directly:
+
+```ruby
+@article = ArticleDecorator.new(Article.first)
+# or, equivalently
+@article = ArticleDecorator.decorate(Article.first)
+```
+
+### Collections
+
+If you have a whole bunch of objects, you can decorate them all in one fell swoop:
+
+```ruby
+@articles = ArticleDecorator.decorate_collection(Article.all)
+# or, for scopes (but not `all`)
+@articles = Article.popular.decorate
+```
+
+If you want to add methods to your decorated collection (for example, for pagination), you can subclass `Draper::CollectionDecorator`:
+
+```ruby
+# app/decorators/articles_decorator.rb
+class ArticlesDecorator < Draper::CollectionDecorator
+ def page_number
+ 42
+ end
+end
+
+# elsewhere...
+@articles = ArticlesDecorator.new(Article.all)
+# or, equivalently
+@articles = ArticlesDecorator.decorate(Article.all)
+```
+
+Draper guesses the decorator used for each item from the name of the collection decorator ("ArticlesDecorator" becomes "ArticleDecorator"). If that fails, it falls back to using each item's `decorate` method. Alternatively, you can specify a decorator by overriding the collection decorator's `decorator_class` method.
+
+Some pagination gems add methods to `ActiveRecord::Relation`. For example, [Kaminari](https://github.com/amatsuda/kaminari)'s `paginate` helper method requires the collection to implement `current_page`, `total_pages`, and `limit_value`. To expose these on a collection decorator, you can simply delegate to `source`:
+
+```ruby
+class PaginatingDecorator < Draper::CollectionDecorator
+ delegate :current_page, :total_pages, :limit_value, to: :source
+end
+```
+
+### Handy shortcuts
+
+You can automatically decorate associated models:
+
+```ruby
+class ArticleDecorator < Draper::Decorator
+ decorates_association :author
+end
+```
+
+And, if you want, you can add decorated finder methods:
+
+```ruby
+class ArticleDecorator < Draper::Decorator
+ decorates_finders
+end
+```
+
+so that you can do:
+
+```ruby
+@article = ArticleDecorator.find(params[:id])
+```
+
+
+## Testing
+
+Draper supports RSpec and Minitest::Rails out of the box, and should work with Test::Unit as well.
+
+### RSpec
+
+Your specs should live in `spec/decorators` (if not, you need to tag them with `type: :decorator`).
+
+In controller specs, you might want to check whether your instance variables are being decorated properly. You can use the handy predicate matchers:
+
+```ruby
+assigns(:article).should be_decorated
+# or, if you want to be more specific
+assigns(:article).should be_decorated_with ArticleDecorator
+```
+
+Note that `model.decorate == model`, so your existing specs shouldn't break when you add the decoration.
+
+Spork users should `require 'draper/test/rspec_integration'` in the `Spork.prefork` block.
+
+
+## Advanced usage
+
+### `ApplicationDecorator`
+
+If you need common methods in your decorators, you can create an `ApplicationDecorator`:
+
+```ruby
+# app/decorators/application_decorator.rb
+class ApplicationDecorator < Draper::Decorator
+# ...
+end
+```
+
+and inherit from it instead of directly from `Draper::Decorator`.
+
+### Enforcing an interface between controllers and views
+
+If you want to strictly control which methods are called in your views, you can restrict the methods that the decorator delegates to the model. Use `denies` to blacklist methods:
+
+```ruby
+class ArticleDecorator < Draper::Decorator
+ # allow everything except `title` and `author` to be delegated
+ denies :title, :author
+end
+```
+
+or, better, use `allows` for a whitelist:
+
+```ruby
+class ArticleDecorator < Draper::Decorator
+ # only allow `title` and `author` to be delegated to the model
+ allows :title, :author
+end
+```
+
+You can prevent method delegation altogether using `denies_all`.
+
+### Adding context
+
+If you need to pass extra data to your decorators, you can use a `context` hash. Methods that create decorators take it as an option, for example
+
+```ruby
+Article.first.decorate(context: {role: :admin})
+```
+
+The value passed to the `:context` option is then available in the decorator through the `context` method.
+
+If you use `decorates_association`, the context of the parent decorator is passed to the associated decorators. You can override this with the `:context` option:
+
+```ruby
+class ArticleDecorator < Draper::Decorator
+ decorates_association :author, context: {foo: "bar"}
+end
+```
+
+or, if you simply want to modify the parent's context, use a lambda that takes a hash and returns a new hash:
+
+```ruby
+class ArticleDecorator < Draper::Decorator
+ decorates_association :author,
+ context: ->(parent_context){ parent_context.merge(foo: "bar") }
+end
+```
+
+### Specifying decorators
+
+When you're using `decorates_association`, Draper uses the `decorate` method on the associated record (or each associated record, in the case of a collection association) to perform the decoration. If you want use a specific decorator, you can use the `:with` option:
+
+```ruby
+class ArticleDecorator < Draper::Decorator
+ decorates_association :author, with: FancyPersonDecorator
+end
+```
+
+For a collection association, you can specify a `CollectionDecorator` subclass, which is applied to the whole collection, or a singular `Decorator` subclass, which is applied to each item individually.
+
+### Scoping associations
+
+If you want your decorated association to be ordered, limited, or otherwise scoped, you can pass a `:scope` option to `decorates_association`, which will be applied to the collection before decoration:
+
+```ruby
+class ArticleDecorator < Draper::Decorator
+ decorates_association :comments, scope: :recent
+end
+```
+
+### Breaking with convention
+
+If, as well as instance methods, you want to proxy class methods to the model through the decorator (including when using `decorates_finders`), Draper needs to know the model class. By default, it assumes that your decorators are named `SomeModelDecorator`, and then attempts to proxy unknown class methods to `SomeModel`. If your model name can't be inferred from your decorator name in this way, you need to use the `decorates` method:
+
+```ruby
+class MySpecialArticleDecorator < Draper::Decorator
+ decorates :article
+end
+```
+
+You don't need to worry about this if you don't want to proxy class methods.
+
+### Making models decoratable
+
+Models get their `decorate` method from the `Draper::Decoratable` module, which is included in `ActiveRecord::Base` and `Mongoid::Document` by default. If you're using another ORM, or want to decorate plain old Ruby objects, you can include this module manually.
+
+
+## Contributors
+
+Draper was conceived by Jeff Casimir and heavily refined by Steve Klabnik and a great community of open source [contributors](https://github.com/drapergem/draper/contributors).
+
+### Core Team
+
+* Jeff Casimir (jeff@jumpstartlab.com)
+* Steve Klabnik (steve@jumpstartlab.com)
+* Vasiliy Ermolovich
+* Andrew Haines
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