# Rep

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```

A library for writing authoritative representations of objects for pages and apis.

## Installation

Add this line to your application's Gemfile:

    gem 'rep'

And then execute:

    $ bundle

Or install it yourself as:

    $ gem install rep

## Usage

`include Rep` into any class. See [nathanherald.com/rep](http://nathanherald.com/rep) for complete docs on every method.

## Examples

```ruby
# imagine Photo is an ActiveRecord model with fields for title, exif, location, and user_id

class PhotoRep
  include Rep

  initialize_with :photo

  fields [:url, :title, :exif, :location, :user] => :default

  forward [:title, :exif, :location] => :photo
  forward :user => :user_rep

  def url
    full_photo_url(photo.name)
  end

  def user
    UserRep.shared(user: photo.user)
  end
end

# imagine User is an ActiveRecord model with fields for name, email, and location

class UserRep
  include Rep

  initialize_with :user

  fields [:name, :email, :location] => :default
  fields [:id, :admin].concat(fields(:default)) => :admin

  forward fields(:admin) => :user
end

# You can now do crazy stuff like
UserRep.new(user: User.first).to_hash.keys # => [:name, :email, :location]

# To save from creating lots of objects, you can use a shared class that is reset fresh
UserRep.shared(user: User.first).to_hash # => { name: "Nathan Herald:, ...

# You can use class to proc (that makes a hash using the shared instance)
User.all.map(&UserRep) # => [{ name: "Nathan Herald" ...

# or maybe find all photos which will embed all users (and only ever make one instance each of PhotoRep and UserRep)
Photo.all.map(&PhotoRep).to_json
```

### Any class

You don't have to have a Rep per model and Rep's can represent multiple objects at once. It's POROs.

```ruby
class ProjectReport
  include Rep
  initialize_with :project, :active_users, :orders
  fields [:name, :date, :count, :total_gross_cost, :cost_per_active_user] => :default
  forward :date => :project
  forward :count => :orders

  def name
    "#{project.name} Report"
  end

  def total_gross_cost
    orders.reduce(0.0) { |memo, order| memo += order.total_gross_cost.to_f }
  end

  def cost_per_active_user
    active_users.count.to_f / total_gross_cost.to_f
  end
end
```

### Rails

A possible controller
```ruby
class PhotosController < ApplicationController
  respond_to :json, :html

  def index
    @photos = Photo.paginate(page: params[:page], per_page: 20)
    respond_with @photos.map(&PhotoRep)
  end

  def show
    @photo = Photo.find(params[:id])
    respond_with PhotoRep.new(photo: @photo)
  end
end
```