Why am I getting "undefined method `flatten'" when calling on an array?

Problem

I am building a script that takes in a column from a CSV that can contain 0 or more ID numbers. I have created an array of the column, however, since some cells have no ID number and some have multiple,I have an array of arrays.

I want to create an array where each element is a single ID (i.e split the IDs from each element in the array to a single element).

Here is my code so far:

require 'csv'
class MetadataTherapyParser

    def initialize (csv)
        @csv = csv
    end

    def parse_csv
        therapy_array = []
        CSV.foreach(@csv) do |csv_row|
            therapy_array << csv_row[0] 
        end
    end

    def parse_therapies(therapy_array) 
        parsed_therapy_array = therapy_array.flatten!
        puts parsed_therapy_array   
    end
end

metadata_parse = MetadataTherapyParser.new ("my_csv_path")
metadata_parse.parse_csv
metadata_parse.parse_therapies(metadata_parse)

Actual Results

I am getting the following error:

in `parse_therapies': undefined method `flatten' for #<MetadataTherapyParser:0x00007fd31a0b75a8> (NoMethodError)

From what I can find online, flatten is the method to use. However I can't seem to figure out why I am getting an undefined method error. I have checked to ensure that therapy_array is indeed an array.

If anyone has encountered this issue before and could offer some advice, it would be greatly appreciated!

Thank you in advance.

Solution

While calling the method parse_therapies instead of passing an array you are passing the metedata_parse, which is an object of MetadataTherapyParser

Try this:

def parse_csv
    therapy_array = []
    CSV.foreach(@csv) do |csv_row|
        therapy_array << csv_row[0] 
    end
    therapy_array
end

Then while calling the methods:

metadata_parse = MetadataTherapyParser.new ("my_csv_path")
therapy_array = metadata_parse.parse_csv
metadata_parse.parse_therapies(therapy_array)

This should pass an Array instead of MetadataTherapyParser object to your parse method.