Example code: Controller I am working on for forms that post to an external API (Airtable) when submitted.

calibration_forms_controller.rb

class CalibrationFormsController < ApplicationController
  # Need not be a registered user to submit a calibration form
  skip_before_action :authenticate_user!

  def form
    # limit current forms available for testing
    valid_forms = ['','straight_edge', 'oven']
    raise ActionController::UnknownAction unless valid_forms.include?(params[:id])
    
    @title = params[:id].gsub('_',' ').titlecase
    @form_to_render = params[:id]
  end

  def submit_form
    # Set @table_name and @client_key
    set_airtable_data
    # decanter gem converts record_params data types to appropriate types for Airtable fields,
    # as defined in app/decanters/calibration_forms_decanter.rb
    decanted_params = CalibrationFormsDecanter.decant(record_params)

    # Hit Airtable post API with decanted form params converted to json; store response
    response = Net::HTTP.post URI("https://api.airtable.com/v0/appyyy.../#{@table_name}"),
      {fields: decanted_params}.to_json,
      "Authorization" => "Bearer #{@client_key}",
      "Content-type" => "application/json"

    # debugging
    unless response.kind_of?(Net::HTTPSuccess)
      Rails.logger.info response.code
      Rails.logger.info response.body
    end

    # On success, present cleared form and notice of success
    if response.kind_of?(Net::HTTPSuccess)
      redirect_to cal_form_path(params[:cal_form_data][:type]), notice: "Record was successfully saved."
    end
  end

  private

  def set_airtable_data
    # API key for Speedie Airtable account
    @client_key = "keyzzz..."
    # Set @table_name from form URL params (pluralized) - **Be sure Airtable Title matches**
    @table_name = params[:cal_form_data][:type].gsub('_','%20').titlecase + 's'
  end

  def record_params
    # Submit all data gathered by form except 'type', since that is only
    # used to find the right table in Airtable
    params.require(:cal_form_data).except(:type).permit!
  end
end