undefined method `fetch_value' for nil:NilClass when using Roo

I am trying to use Roo to import data from an Excel spreadsheet into a table (data_points) in a Rails app.

I am getting the error:

undefined method `fetch_value' for nil:NilClass

and that error references my data_point.rb file at line (see below for full code excerpt):

data_point.save!

The "Application Trace" says:

app/models/data_point.rb:29:in `block in import'
app/models/data_point.rb:19:in `import'
app/controllers/data_points_controller.rb:65:in `import'

I am puzzled by this because a "find all" in my entire app shows no instance of fetch_value

Here is the other code in my app:

In my model, data_point.rb:

class DataPoint < ActiveRecord::Base
attr_accessor :annual_income, :income_percentile, :years_education

def initialize(annual_income, income_percentile, years_education)
    @annual_income = annual_income
    @income_percentile = income_percentile
    @years_education = years_education
end

def self.import(file)
    spreadsheet = open_spreadsheet(file)
    header = spreadsheet.row(1)
    (2..11).each do |i| 
        annual_income = spreadsheet.cell(i, 'A')
        income_percentile = spreadsheet.cell(i, 'B')
        years_education = spreadsheet.cell(i, 'C')
        data_point = DataPoint.new(annual_income, income_percentile, years_education)
        data_point.save!
    end
end 

def self.open_spreadsheet(file)
    case File.extname(file.original_filename)
    when ".xlsx" then Roo::Excelx.new(file.path)
    else raise "Unknown file type: #{file.original_filename}"
    end
end
end

In my controller, data_points_controller.rb I have added, in addition to the standard rails framework:

def import
    DataPoint.import(params[:file])
    redirect_to root_url, notice: "Data points imported."
end

In the Excel file I'm using, the header row has column names that are exactly the same as the 3 attributes noted above for DataPoints: annual_income, income_percentile, years_education

P.s. I have already watched RailsCast 396: Importing CSV and Excel, and read the comments many times. I think I am struggling with translating the example code to Rails 4 and / or my assignment of individual attributes (vs. the approach used in the RailsCast).

Thanks in advance for any help!

It seems you had some leftovers from your non rails practice, as we found in the comments. Notably, the overwritten initialize method, and the attr_accessor for each of the attributes. Removing them (and fixing the DataPoint.new() for the correct format) was all that was needed.