Error handling of csv upload in rails - ruby-on-rails

Question

I have this import method in my active record which I use to import the csv file. I want to know how to do the error handling of this in the active record.
class SheetEntry < ActiveRecord::Base
unloadable
belongs_to :user
belongs_to :project
belongs_to :task
validate :project_and_task_should_be_active
def self.import(csv_file)
attributes = [:user_id, :project_id, :task_id, :date, :time_spent, :comment]
errors=[]
output = {}
i=0
CSV.foreach(csv_file, headers: true, converters: :date).with_index do |row,j|
entry_hash= row.to_hash
entry_hash['Project'] = SheetProject.where("name= ?" , entry_hash['Project']).pluck(:id)
entry_hash['Task'] = SheetTask.where("name= ?" , entry_hash['Task']).pluck(:id)
entry_hash['Date'] = Time.strptime(entry_hash['Date'], '%m/%d/%Y').strftime('%Y-%m-%d')
entry_hash['Time (Hours)'] = entry_hash['Time (Hours)'].to_f
firstname = entry_hash['User'].split(" ")[0]
lastname = entry_hash['User'].split(" ")[1]
entry_hash['User'] = User.where("firstname=? AND lastname=?",firstname,lastname).pluck(:id)
entry_hash.each do |key,value|
if value.class == Array
output[attributes[i]] = value.first.to_i
else
output[attributes[i]] = value
end
i += 1
end
entry=SheetEntry.new(output)
entry.editing_user = User.current
entry.save!
end
end
def project_and_task_should_be_active
errors.add(:sheet_project, "should be active") unless sheet_project.active?
errors.add(:sheet_task, "should be active") if sheet_task && !sheet_task.active?
end
end
I want to know how to show the error if there is a nil object returned for either entry_hash['Project'] or entry_hash['Task'] or for any of the fields in the csv.
For example: If the user had entered the wrong project or wrong task or wrong date. I want the error to be shown along with the line no and stop the uploading of the csv. Can someone help?

Answer 1

You can use begin and rescue statements to handle errors in any ruby classes.
You can use the rescue block to return the Exception e back to the caller.
However, you cannot call errors.add method to add error because #errors is an instance method which is not accessible inside class method self.import.
def self.import(csv_file)
begin
attributes = [:user_id, :project_id, :task_id, :date, :time_spent, :comment]
errors=[]
output = {}
i=0
CSV.foreach(csv_file, headers: true, converters: :date).with_index do |row,j|
...
end
rescue Exception => e
return "Error: #{e}"
end
end