About the range and scope where Day16 variables can be used

Variable passing summary

ReviewApp

def post_review
  post = {}
  puts "Please enter a genre:"
  post[:genre] = gets.chomp
  puts "Please enter a title:"
  post[:title] = gets.chomp
  puts "Please enter your thoughts:"
  post[:review] = gets.chomp
  line = "---------------------------"

  #Drawing a review
  puts "Genre: #{post[:genre]}\n#{line}"
  puts "title: #{post[:title]}\n#{line}"
  puts "Impressions:\n#{post[:review]}\n#{line}"

  #Add to array object
  posts << post
end

↑ In this case, posts is not defined in the post_review method, so it is NG. In principle, only variables defined in the method can be used. To be able to use this, we use an argument.

ReviewApp

def post_review (a_posts)
  post = {}
  puts "Please enter a genre:"
  post[:genre] = gets.chomp
  puts "Please enter a title:"
  post[:title] = gets.chomp
  puts "Please enter your thoughts:"
  post[:review] = gets.chomp
  line = "---------------------------"

  #Drawing a review
  puts "Genre: #{post[:genre]}\n#{line}"
  puts "title: #{post[:title]}\n#{line}"
  puts "Impressions:\n#{post[:review]}\n#{line}"

  #Add to array object
  a_posts << post

  # a_returns posts to the method caller
  return a_posts
end

#Generate array object posts
posts = []

while true do
  #Display menu
  puts "Number of reviews: 0"
  puts "[0]I write a review"
  puts "[1]Read reviews"
  puts "[2]Quit the app"
  input = gets.to_i

  if input == 0 then
    posts = post_review(posts)  # post_Call review method
  elsif input == 1 then
    read_reviews                # read_Call the reviews method
  elsif input == 2 then
    end_program                 # end_Call the program method
  else
    exception                   #call the exception method
  end
end

The caller should assign this return value to the variable posts. I was able to add review information posts to the array object posts that manage reviews by using arguments.

① Call the post_review method with posts = post_review (posts) with posts as an argument

② In the post_review method, copy posts to a variable called a_posts.

③ Add a hash to a_posts in the post_review method and return a_posts

④ Substitute the returned a_posts for posts by posts = post_review (posts)

def multi(number)         #In the method definition, number is used as a formal argument.
  puts number * number
end

puts "Please enter some number"
value = gets.to_i

multi(value)             #When actually using the multi method, I put the value instead of the number.