Rails CSV import from scratch - ruby-on-rails

Question

I am rather new to using rails and website programming, apologizes for possible basic questions.
My website needs to upload a CSV file with the format:
Course_name #header
course1
Module_name #header
module1
Task_name,Task_description,Task_expected_result #header
mod1 task1 test,mod1 task2 test description,mod1 task1 test result
mod1 task2 test,mod1 task2 test description,mod1 task2 test result
mod1 task3 test,mod1 task3 test description,mod1 task3 test result
Module_name #header
module2
Task_name,Task_description,Task_expected_result
mod2 task1 test,mod2 task1 test description,mod2 task1 test result
mod2 task2 test,mod2 task2 test description,mod2 task2 test result
My database is set up that a course will have many modules, which in turn have many tasks.
Course > many modules > many tasks.
On my website I would like to upload the .csv file and then hit a button to upload the course.
I need the reading of the file, and thus the creation of the table entries to go as following:
read course_name until blank line is hit, create course using that name, grab the course_id of the newly created course.
read Module_name until blank line is hit, create the module using that name and the course_id(is how they are connected) and grab that module_id.
then read task_name, task_description and task_expected_results and create a task using all those values and the module_id, do this until a blank line is read.
then if not EOF and another module_name is read, repeat from module creation to task creation until EOF.
I know this is a lot to ask, I've tried searching online for help but i have not had any luck there. Any help with model/controller/view code would be appreciated greatly.

Answer 1

You will need to modify this in order to get it to find/populate your objects, but this uses strings to get the data from the CSV.
First off I split your "CSV" based on there being a blank line gap between sections (as I said before, this is a lot like trying to send several dictionary/database files inside a CSV, rather than using a better computer interchange format)
using the sample of view that you added to the comment (as HAML):
= form_with(multipart: true) do |f|
= f.file_field :file, accept: '.csv'
= submit_tag 'Read CSV'
your file will now be passed into the Rails as an ActionDispatch::Http::UploadedFile.
We can access the contents of this file, using the `#read' method:
mycsv = params[:file].read
my code for splitting, formatting, etc (assuming that the format of the file never changes):
require 'csv'
# first split the "string" into sections
csvarr = mycsv.split(/^$/).map(&:strip)
# the first section is going to be the course. so "shift" it out of the array,
# leaving us with an even number of remaining elements.
# since it's assumed that the first section will be the course, I don't bother
# checking that it is, and just store it's value
course_name = csvarr.shift.lines.last
# You probably want to do a "course = Course.find_or_create_by(name: course_name)"
# now loop through the remaining elements, 2 at a time
csvarr.each_slice(2) do |mod|
# the first element in a block of 2 will be the header
modname = mod[0].lines.last
# You probably want to do a "module = Module.find_or_create_by(course: course, name: modname)"
# the second element will be the associated data
modcsv = CSV.parse(mod[1], headers: true)
# loop through the data to show that we have it all correctly
modcsv.each do |task|
puts "Course: #{course_name} Module: #{modname} Task: #{task["Task_name"]}\n"
end
end