RhoConnect Source Adapters (Ruby)
===

## Generating the Source Adapter from RhoStudio

To generate a RhoConnect source adapter and create the associated Controller/Model templates, open your RhoConnect project in RhoStudio. Then right-click on the project in the Project Explorer and select New->RhoConnect Source Adapter.

<img src="http://rhodocs.s3.amazonaws.com/rhoconnect-tutorial/menu-new-rhoconnect_source-adapter.png"/>

In the Source Adapter Information window, enter the name for your source adapter.

Click the Finish button to create the source adapter.

<img src="http://rhodocs.s3.amazonaws.com/rhoconnect-tutorial/source-adapter-information.png"/>

After pressing the Finish button, you'll see the RhoConnect source adapter generator script output in the output console (Rhomobile build console).

<img src="http://rhodocs.s3.amazonaws.com/rhoconnect-tutorial/rhoconnect-source-generator-output.png"/>

## Generating the Source Adapter from the Command Line

To generate a source adapter for your RhoConnect application, you can run the `rhoconnect source` command within your application directory.

    :::term
    $ rhoconnect source
    Usage: rhoconnect source name [options] [args]

    Generates a new source adapter.

    Required:
      name        - the source adapter name(i.e. product)


    Options specific for this generator:

    General options:
        -p, --pretend                    Run, but do not make any changes.
        -f, --force                      Overwrite files that already exist.
        -s, --skip                       Skip files that already exist.
        -d, --delete                     Delete files that have previously been generated with this generator.
            --no-color                   Don't colorize the output
        -h, --help                       Show this message
            --debug                      Do not catch errors

For the storeserver application example, within the storeserver directory, run:

    :::term
    $ rhoconnect source product
    Generating with source generator:
         [ADDED]  models/ruby/product.rb
         [ADDED]  controllers/ruby/product_controller.rb
         [ADDED]  spec/models/ruby/product_spec.rb
         [ADDED]  spec/controllers/ruby/product_controller_spec.rb

## Understanding the Generated Controller File

The generated source adapter's controller file (in this case, product_controller.rb) is similar to the code listing below.
Its purpose is to define the RhoConnect application HTTP end point and to register the corresponding SYNC routes.
Under the hood - it's an isolated Sinatra application designated to handle all incoming Product requests:

    :::ruby
    class ProductController < Rhoconnect::Controller::Base
      register Rhoconnect::EndPoint

      # add all SYNC routes
      register Rhoconnect::Handler::Sync

      # add your custom Product routes here
    end

## Understanding the Generated Model File

The generated source adapter's model file (in this case, product.rb) is similar to the code listing below:

    :::ruby
    class Product < Rhoconnect::Model::Base
      def initialize(source)
        super(source)
      end

      def login
        # TODO: Login to your data source here if necessary
      end

      def query
        # TODO: Query your backend data source and assign the records
        # to a nested hash structure called @result. For example:
        # @result = {
        #   "1"=>{"name"=>"Acme", "industry"=>"Electronics"},
        #   "2"=>{"name"=>"Best", "industry"=>"Software"}
        # }
        raise Rhoconnect::Model::Exception.new("Please provide some code to read records from the backend data source")
      end

      def create(create_hash)
        # TODO: Create a new record in your backend data source
        # If your rhodes rhom object contains image/binary data
        # (has the image_uri attribute), then a blob will be provided
        raise "Please provide some code to create a single record in the backend data source using the create_hash"
      end

      def update(update_hash)
        # TODO: Update an existing record in your backend data source
        raise "Please provide some code to update a single record in the backend data source using the update_hash"
      end

      def delete(delete_hash)
        # TODO: write some code here if applicable
        # be sure to have a hash key and value for "object"
        # for now, we'll say that its OK to not have a delete operation
        # raise "Please provide some code to delete a single object in the backend application using the object_id"
      end

      def logoff
        # TODO: Logout from the data source if necessary
      end
    end

During generation of the model, the `settings/settings.yml` file will be updated with some default options for the corresponding source:

    :::yaml
    :sources:
        Product:
        :poll_interval: 300


## Source Adapter API

### Source Adapter Controller API (Ruby)

You can use the following methods and techniques inside of your source adapter controller.

* [@model](/rhoconnectapi/source-adapter-controller-api-ruby#@model) - Access to the source adapter's model instance.
* [params,request,response](/rhoconnectapi/source-adapter-controller-api-ruby#sinatra-context) - Allows to use any standard Sinatra context objects.
* [Sinatra framework](/rhoconnectapi/source-adapter-controller-api-ruby#sinatra-features) - Allows to use any standard Sinatra features.

### Source Adapter Model API (Ruby)

You can write the following methods for your source adapter model. These methods will be called by the controller at run-time and allow your source adapter model to interact with your backend service.

* [login](/rhoconnectapi/source-adapter-model-api-ruby#login) - Login to your backend service (optional).
* [logoff](/rhoconnectapi/source-adapter-model-api-ruby#logoff) - Logoff from your backend service (optional).
* [query](/rhoconnectapi/source-adapter-model-api-ruby#query) - Query your backend service and build a hash of hashes (required).
* [search](/rhoconnectapi/source-adapter-model-api-ruby#search) - Search your backend based on params and build a hash of hashes (optional).
* [create](/rhoconnectapi/source-adapter-model-api-ruby#create) - Create a new record in the backend (optional).
* [update](/rhoconnectapi/source-adapter-model-api-ruby#update) - Update an existing record in the backend.
* [delete](/rhoconnectapi/source-adapter-model-api-ruby#delete) - Delete an existing record in the backend.
* [current_user](/rhoconnectapi/source-adapter-model-api-ruby#currentuser) - Returns the current user which called the adapter's model.
* [stash_result](/rhoconnectapi/source-adapter-model-api-ruby#stashresult) - Saves the current state of `@result` to redis and assigns it to `nil`.
* [store_blob](/rhoconnectapi/source-adapter-model-api-ruby#store_blob) - Save the incoming blob data into permanent storage for the future processing.
* [get_data](/rhoconnectapi/source-adapter-model-api-ruby#get_data) - Get the model document data from Store.

## Data Partitioning

Data is stored in RhoConnect using [redis sets](http://redis.io/commands#set).  The `@result` hash from the `query` method is stored in redis and referred to as the Master Document or MD.

The MD is referenced in RhoConnect by a corresponding partition.  Source adapters can partition data in two ways: user and app.  As you might have guessed, user partitioning stores a copy of the source adapter MD for each user (one copy shared across all devices for a given user).

Likewise, app partitioning stores one copy of the source adapter MD for the entire application (all users and devices share the same data).  App partitioning can be particularly useful if you have source adapter models which retrieve large amounts of data that is fixed from user to user, for example a global product catalog.  Using app partitioning wherever possible ***greatly reduces*** the amount of data in redis.

### User Partition
User partitioning is the default mode for source adapters, however you can explicitly define it in `settings/settings.yml` with:

    :::yaml
    :sources:
      Product:
      :poll_interval: 300
      :partition_type: user

### App Partition
Enable app partitioning the same way:

    :::yaml
    :sources:
      Product:
      :poll_interval: 300
      :partition_type: app

Now you have a single copy of the `Product` source adapter dataset for all users.

## Pass Through
RhoConnect provides a simple way to keep data out of redis.  If you have sensitive data that you do not want saved in redis, add the `pass_through` option in settings/settings.yml for each source:

    :::yaml
    :sources:
      Product:
      :pass_through: true

**NOTE: When running query or search the entire data set will be returned from your backend service. **

## Redis Interface
RhoConnect provides a simple redis interface for saving/retrieving arbitrary data.  This is useful if you want to save data in your application to be used later (i.e. in an async job or a subsequent source adapter execution).

    :::ruby
    Store.put_value('hello','world')

    Store.get_value('hello') #=> 'world'

    # You can store nested hashes too!
    Store.put_data(
      'mydata',
      {
        '1' => { 'hello' => 'world' }
      }
    )

    Store.get_data('mydata') #=> { '1' => { 'hello' => 'world' } }

## Handling Exceptions
If your source adapter model raises an instance of `Rhoconnect::Model::Exception`, the resulting message will be sent to the client's sync callback(in `@params['error_message']`).  See the rhodes [sync exception handling docs](/rhodes/synchronization#handling-exceptions) for more details.

You can use `Rhoconnect::Model::Exception` as a convenient way to notify your application of various error conditions.

For example, your delete method might check the web service HTTP response code was 200 to make sure the record was deleted:

    :::ruby
    def delete(delete_hash)
      rest_result = RestClient.delete("#{@base}/#{delete_hash['id']}")
      if rest_result.code != 200
        raise Rhoconnect::Model::Exception.new("Error deleting record.")
      end
    end

**NOTE: When your adapter method raises an exception, no data is removed from the adapter's master document.**

The following exceptions are provided for convenience:

### `Rhoconnect::Model::LoginException`
Useful to raise in your model's login method if it failed.

### `Rhoconnect::Model::LogoffException`
Similar to login, raise this if your model's logoff failed.

### `Rhoconnect::Model::ServerTimeoutException`
Raise if your backend service connection times out.

### `Rhoconnect::Model::ServerErrorException`
Raise this if your backend service returns a non-successful response.


## Handling Conflicts

Handling conflicts in RhoConnect follows the same pattern as handling exceptions.  Once your model method has detected a conflict, you can raise a `Rhoconnect::Model::ObjectConflictError` which will be sent to your application's sync callback.

### `Rhoconnect::Model::ObjectConflictError`
Raise this if your model has detected a conflict.

    :::ruby
    def update(update_hash)
      obj_id = update_hash['id']
      update_hash.delete('id')
      rest_result = RestClient.put("#{@base}/#{obj_id}",:product => update_hash)
      if rest_result.code != 200
        raise Rhoconnect::Model::ObjectConflictError.new("Conflict detected updating the object.")
      end
    end

## Sample Model
Here's a complete example of how the completed [product model might look](https://github.com/rhomobile/store-server/blob/master/sources/product.rb):

    :::ruby
    require 'json'
    require 'rest_client'

    class Product < Rhoconnect::Model::Base

      def initialize(source)
        @base = 'http://rhostore.herokuapp.com/products'
        super(source)
      end

      def query(params=nil)
        rest_result = RestClient.get("#{@base}.json").body

      if rest_result.code != 200
        raise Rhoconnect::Model::Exception.new("Error connecting!")
      end
        parsed = JSON.parse(rest_result)

        @result={}
        parsed.each do |item|
          @result[item["product"]["id"].to_s] = item["product"]
        end if parsed
      end

      def create(create_hash)
        res = RestClient.post(@base,:product => create_hash)

        # After create we are redirected to the new record.
        # We need to get the id of that record and return
      # it as part of create so rhoconnect can establish a link
      # from its temporary object on the client to this newly
      # created object on the server
        JSON.parse(
        RestClient.get("#{res.headers[:location]}.json").body
      )["product"]["id"]
      end

      def update(update_hash)
        obj_id = update_hash['id']
        update_hash.delete('id')
        RestClient.put("#{@base}/#{obj_id}",:product => update_hash)
      end

      def delete(delete_hash)
        RestClient.delete("#{@base}/#{delete_hash['id']}")
      end
    end

## Compatibility with older versions of RhoConnect

The RhoConnect Source Adapter Controller/Model concept has been introduced in RhoConnect 4. In previous versions, a Source Adapter consisted only of one class - which is now has been moved to Source Adapter model. "Controller" part of the Source Adapter has been hidden inside of the RhoConnect library code. This posed a significant obstacle in a way how the developer could utilize the code and the common techniques. To overcome this obstacle, RhoConnect 4 provides you with direct access to the Controller allowing you to customize route behavior and utilize all of the powerful sinatra plugins/extensions that are available.

At the same time, applications that were written using the pre-4.0 versions of RhoConnect will still continue to function without modifications for at least one version cycle. This is accomplished by providing the "default" implementation of the controller for the pre-4.0 Source Adapters. All the Model APIs that are described throughout the documentation are still applicable to the pre-4.0 Source Adapters. In this sense - the RhoConnect 4 Source Adapter Model class and pre-4.0 Source Adapter are interchangeable. 

However, we strongly recommend migrating your pre-4.0 application using this [guide](migration).  RhoConnect 4 will print a warning at startup if it detects a pre-4.0 code structure.

    RhoConnect has detected that you're using deprecated Application class.

      Application class support will be removed in RhoConnect 4.1.
      Please, migrate your Application class into ApplicationController.

      For more details, see RhoConnect Migration guidelines at 
      docs.rhomobile.com

    RhoConnect has detected that you're using deprecated SourceAdapter classes.

      SourceAdapter class support will be removed in RhoConnect 4.1.
      Please, migrate your SourceAdapter classes into RhoConnect Models.

      For more details, see RhoConnect Migration guidelines at
      docs.rhomobile.com