[Ruby] How to calculate the total amount using the initialize method and class variables


There are many ways to get the total amount.

This time, we will use the ** initialize method and theclass variable**.

table of contents

--Practice --Problem --Conditions (configuration) --Answer (commentary) --Process --Supplement

--Summary --References



Use the initialize method and class variables to output the total amount of fruit.

Condition (configuration)

--Class variables - sum

--Class method - get_sum

--Instance variables - name - price

Answer (commentary)

Answer example

class Fruits
  attr_reader :name, :price #Make it readable
  @@sum = 0 #Variable definition
  def initialize(name, price) #name as an argument in the initialize method,Receive price
    @name  = name             #Instance [email protected] name
    @price = price            #Instance [email protected] price
    @@sum += price            # @@Add the total amount of each fruit to sum
  #Fruit name and price
  def cost
    puts "#{name}The price of#{price}It is a circle."

  #Total amount of fruit
  def self.get_sum
    puts "The total price is#{@@sum}It's a yen!"

#Instance generation
apple  = Fruits.new('Apple', 200)
banana = Fruits.new('banana', 150)
melon  = Fruits.new('melon', 500)


#Terminal output result

#The price of an apple is 200 yen.
#The price of bananas is 150 yen.
#The price of melon is 500 yen.
#The total price is 850 yen!


  1. Instance generation

--Pass arguments into the class --initialize is called


--Instance variable definition --Add price of each fruit to @@ sum

  1. Define a method so that it can be output to the terminal

  2. Method call


--You can use instance variables without @ by using attr_reader. (In code, ** name and price ** of ** cost method **)


--initialize is called when instantiating --Class variables can be defined by prefixing the variable with @@ --Getter methods can be defined by using attr_reader --Setter methods can be defined by using attr_writer --Getter / setter methods can define both by using attr_accessor


-Ruby 3.0.0 Reference Manual (Variables and Constants) -[Ruby] attr_accessor method beginner's guide ~ Let's understand how to use and why it is necessary -[Ruby] Understanding "getters" and "setters" -About ruby ​​variables

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