NoMethodError: undefined method `submission' for HTTParty - ruby-on-rails

Question

I'm currently working on a Rails application where I am trying to submit a form to the FormStack API. The request look as follows.
This is what the requests looks like:
POST /api/v2/form/12345/submission.json HTTP/1.1
Host: www.formstack.com
Authorization: Bearer YOUR_APP_OAUTH_TOKEN
Accept: application/json
Content-Type: application/json
field_12345=Example&field_12346=Answer
I'm trying to implement that using Httparty on the library I created to make the requests to this API service.
module FormStack
class Form
include HTTParty
attr_reader :form_id
base_uri "https://www.formstack.com/api/v2"
def initialize
#access_token = ENV.fetch('FORMSTACK_ACCESS_TOKEN')
#form_id = ENV.fetch('FORMSTACK_FORM_ID')
end
def create_form
self.class.get(relative_uri, headers: headers)
end
def submission
self.class.post(create_submission_uri, headers: headers, query: query)
end
private
def relative_uri
"/form/#{#form_id}/field.json"
end
def create_submission_uri
"form/#{#form_id}/submission.json"
end
def headers
{
"Accept" => "application/json",
"Content-Type" => "application/json",
"Authorization" => "Bearer #{#access_token}"
}
end
def query
{
"field_66563890" => "blah",
"field_66563757" => "something"
}
end
end
end
controller
class FormsController < ApplicationController
def display_form
#form = FormStack::Form.new().create_form
end
def create
#form.submission
redirect_to 'localhost:3000'
end
end
This are the routes
get '/forms/display_form', to: 'forms#display_form'
post '/forms/submit', to: "forms#create"

Answer 1

First of all, I've got a couple general ruby things for you:
When you call FormStack::Form.new().create_form you actually don't need the () after .new -- ruby knows to call the method with no arguments even if you exclude the parens.
I'm not quite sure how you're calling FormsController::display_form from FormsController::create, but for now I'll just assume that you're using magic.
Anyways, on to my answer. As your error message states, the error is related to you calling submission on something which does not have a submission method. With that knowledge, we can look at what Object you're calling submission on in this line:
#form.submission
It looks like you're calling submission on #form. Well, let's go and look at where you declare #form:
#form = FormStack::Form.new().create_form
Let's break that declaration down into its parts. First, with FormStack::Form.new(), you're creating a new instance of FormStack::Form. So far so good. FormStack::Form has a submission method defined on it. But then, you call create_form on it. So, let's look at what create_form does:
def create_form
self.class.get(relative_uri, headers: headers)
end
create_form calls a method provided by HTTParty, get. The get method returns a HTTParty::Response Object. So, let's parse through the line where you set #form again. Broken down, what you're doing is this:
#form = FormStack::Form # This line sets the variable to a constant
#form = #form.new # This line sets the variable to be an instance of FormStack::Form
#form = #form.create_form # This line sets #form to be an instance of HTTParty::Reponse
As you can see, at the end we've set #form to an instance of HTTParty::Reponse instead of FormStack::Form, and since there's not submission method for HTTParty::Response that's why you get the error.
Based on this exploration, we can see that the fix would be to set #form to a FormStack::Form object instead, which we can do by changing the display_form action to be:
def display_form
#form = FormStack::Form.new
#form.create_form
end