csv_user.rb

require './user.rb'

def mainmenu
    puts 'select an option please
    1.- new user
    2.- delete user
    3.- consult user
    4.- exit
  type a number: '

  option=gets.chomp

  case option
  when '1' then create_new_user
  when '2' then delete_user
  when '3' then consult_user
  when '4' then Process.exit
  end
end

def create_new_user
  user = User.new
  p 'name'
  user.name = gets.chomp
  p'age'
  user.age = gets.chomp
  p'phone'
  user.phone = gets.chomp
  p'address'
  user.address=gets.chomp
  user.save
  mainmenu
end

def delete_user
  puts 'please type the name of the user'
  name = gets.chomp
  user = User.find_by_name name
  user.delete
  mainmenu
end

def consult_user
  puts 'please type the name of the user'
  name = gets.chomp
  user = User.find_by_name name
  if user
    puts ">> User: #{user}"
  else
    puts">> User #{name} doesn't exist"
  end
  mainmenu
end

mainmenu

data.csv

user.rb

class User
  attr_accessor :name, :age, :phone, :address 

  def self.filepath
    'data.csv' 
  end

  def filepath
    User.filepath
  end

  def self.new(args=nil)
    user = super
    unless args.nil? or args.empty?
      if args.is_a? Hash
        user.name, user.age, user.phone, user.address = args[:name], args[:age], args[:phone], args[:adrress]
      elsif args.is_a? Array
        user.name, user.age, user.phone, user.address = args[0], args[1], args[2], args[3]
      end
    end
    user
  end

  def save
    File.open(filepath,'a') do |file|
      file.puts("#{self.name}, #{self.age}, #{self.phone}, #{self.address}") 
    end
  end
  
  def self.find_by_name(name)
    File.open(filepath,'r') do |file|
      user_line = file.select{|line| line.start_with? name }.first
      user_array =  user_line.chop.split(',') if user_line
      User.new( user_array ) if user_array
    end
  end

  def delete
    file_content =[]
    File.open(filepath,'r') do |file|
      file_content = file.select{|line| !line.start_with?(@name) }.collect{|line| line.chop }    
    end
    File.open(filepath,'w') do |file|
      file_content.each{|line| file.puts line }
    end
  end

  def to_s
    "#{self.name}, #{self.age}, #{self.phone}, #{self.address}" 
  end

end