I have 3 classes that hare related through inheritance (it's a course exercise)

I have a Brand < Product < DBHandler classes

They are in a subfolder of the project, and all of them use require to access each other:

├── class
│   ├── Brand.rb
│   ├── Category.rb
│   ├── DBHandler.rb
│   └── Product.rb
├── db
│   ├── catalogo_categorias.txt
│   ├── catalogo_marca.txt
│   ├── catalogo_producto.txt
│   └── inventario_final.txt
├── init.rb
└── README.md

Clases

The Product file has in it:

require "#{Dir.pwd}/class/DBHandler"

class Product < DBHandler
  attr_reader :key, :final_price, :db
  attr_accessor :name, :unit, :brand, :category, :price

  def initialize(name, unit, brand, category, price)
    @name = name
    @unit = unit
    @brand = brand
    @category = category
    @price = price
    @final_price = set_final_price
    @db = DBHandler.new
    @key = set_key
  end

  def set_key
    @key = "#{@db.how_many 1}#{self.name[0..2].upcase}3BS"
  end

  def set_final_price
    @final_price = self.price * 1.19
  end

  def search_product(search_expresion)
    @db.db_search(search_expresion)
  end

  def alta_product
    @db.write(
      "#{key},#{name},#{unit},#{brand},#{category},#{price},#{final_price}\n"
    )
  end
end

and the Brand file has:

require "#{Dir.pwd}/class/Product"

class Brand < Product
  attr_reader :brand_key, :a_brands, :q_brands
  attr_accessor :brand

  def initialize(brand)
    # use super to use parent's attributes
    super(brand)
    @brand_key = set_brand_key
    @a_brands = get_file.read
                        .split("\n")
                        .map { |abrand| abrand.split(',') }
    @q_brands = @a_brands.count
  end

  def set_brand_key
    "#{@q_brands}#{self.brand[0..2].upcase}3BS"
  end

  def get_file
    File.open("#{Dir.pwd}/db/catalogo_marca.txt")
  end

  def alta_brand
    get_file.write("#{@brand_key},#{@brand}", mode: 'a')
  end
end

Init file

All the files are called from the init.rb file in order to call some instance methods.

this is my Init.rb file first lines.

require './class/Product'
require './class/Brand'
require './class/DBHandler'
require './class/Category'

The problem

when I want to create a new instance of Brand class, I have tried:

1. brand = Brand.new(name, unit, brand, category, price) and it returns wrong number of arguments (given 5, expected 1) (ArgumentError)
2. brand = Brand.new(brand) and it returns wrong number of arguments (given 1, expected 5) (ArgumentError)

I don't know what may I doing wrong. I need to create a Brand instance with only brand argument

CodePudding user response：

Your problem is here

super(brand)

This is saying "call the parent constructor with brand as the only argument". The parent constructor is Product#initialize, which takes five arguments. So no matter how you call Brand#initialize, it's going to fail since it calls Product#initialize with the wrong number of arguments. You need to call super with all five.

But I challenge the frame. Subclassing is a very tight coupling, an "is-a" relationship. What you're claiming is that every brand is a product, and I fail to see how that's true. So rather than fixing the super call, you might reconsider your design and ask yourself if you really meant to make a subclass.