Combine API data with local data in Rails

Question

I am working with the GoCardless API in my Rails 3 application. I have a subscription model which has a resource_id column which matches the id of the remote record.

I am trying to get extra information for a local subscription record from the API.

Subscription Index View

<% @subscriptions.each do |subscription| %>
  <tr>
    <td><%= subscription.resource_id %></td>
    <td><%= subscription.resource_type %></td>
    <td><%= subscription.signature %></td>
    <td><%= subscription.state %></td>
    <td><%= @gocardless.next_interval_start %></td>
    <td><%= link_to 'Show', subscription %></td>
    <td><%= link_to 'Edit', edit_subscription_path(subscription) %></td>
    <td><%= link_to 'Destroy', subscription, method: :delete, data: { confirm: 'Are you sure?' } %></td>
  </tr>
<% end %>

Subscription Controller

def index
 @subscriptions = Subscription.all
 @gocardless = GoCardless::Merchant.find("XXXXXXXXXX").subscriptions

 respond_to do |format|
   format.html # index.html.erb
   format.json { render json: @subscriptions }
 end
end

As you can see I'm using the following line to retrieve the next interval start date

<%= @gocardless.next_interval_start %>

This doesn't work and returns nil. However, if I change it to the following all records show the value from the first record from the API.

<%= @gocardless.first.next_interval_start %>

According to the GoCardless API documentation you can lookup a subscription using the following:

GoCardless::Subscription.find("XXXXXXXXXX")  # =>  #<GoCardless::Subscription ...>

So, my question. How do I pass the current subscription resource_id to the API so that I can view the next_internal_start value for each of the local subscription records?

Update

Using Adam's example below I get a 404 response from GoCardless. I think it's due to me not setting the merchant ID in the request. When I change the method to:

def gc_subscription
  @gc_subscription ||= GoCardless::Merchant.find("MERCHANTID").subscriptions.find(self.resource_id)
end

I get undefined methodinterval' for #` for any attribute I try and request using the following code:

<% for subscription in @subscriptions %>
 <%= subscription.gc_subscription.amount
<% end %>

When using the same code to get local content it works as expected:

<% for subscription in @subscriptions %>
 <%= subscription.resource_id %>
<% end %>

I've checked that the value I am trying to retrieve is available in the API. https://sandbox.gocardless.com/docs/api_guide#resources-available

Update Two

As before calling the first result works using Adam's method:

<%= subscription.gc_subscription.first.amount %>

This returns 2.5 which is the value of the first subscription.

adamcooke · Accepted Answer · 2012-11-17 10:41:04Z

2

If I had a local Subscription model which linked to a remote data source I would have a method like this on my Subscription model which provided access to the remote object:

def gc_subscription
  @gc_subscription ||= GoCardless::Subscription.find(self.resource_id)
end

Then you can access this method as necessary without any need for any GC logic in the view or controller. For example:

for subscription in @subscriptions
   subscription.gc_subscription.some_method #=> "output"
end

Or, if you are only working with one subscription:

subscription = Subscription.find(id)
subscription                 #=> Your local Subscription instance
subscription.gc_subscription #=> GoCardless::Subscription instance

With it configured like that, you will be able to remove the @gocardless from your controller and replace your view with this:

<% @subscriptions.each do |subscription| %>
  <tr>
    <td><%= subscription.resource_id %></td>
    <td><%= subscription.resource_type %></td>
    <td><%= subscription.signature %></td>
    <td><%= subscription.state %></td>
    <td><%= subscription.gc_subscription.next_interval_start %></td>
    <td><%= link_to 'Show', subscription %></td>
    <td><%= link_to 'Edit', edit_subscription_path(subscription) %></td>
    <td><%= link_to 'Destroy', subscription, method: :delete, data: { confirm: 'Are you sure?' } %></td>
  </tr>
<% end %>

I hope that helps.

answered Nov 17, 2012 at 10:41

adamcooke

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3 Comments

RocketR Over a year ago

I'd just add that with a large number of subscriptions this would be pretty slow. More efficient is to retrieve all data by a single request to the API.

dannymcc Over a year ago

Thanks Adam. I'm still a little confused. I've added the method into the subscription model and I've removed the GC logic from the controller. In the index view I have <% @subscriptions.each do |subscription| %> and then called <%= subscription.gc_subscription.next_interval_start %>. I get a 404 error though. I've checked that the subscription table has only one resource_id that's valid. Should I have subscription = Subscription.find(id) in the controller?

dannymcc Over a year ago

I think it might be 404 because I'm not setting my merchant ID.

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