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Ruby Ruby Collections Build a Grocery List Program Build a Grocery List Program: Part 3

Posted by darrell mayson
darrell mayson
5,215 Points

Error thrown: "in `print_list': undefined method `each' for nil:NilClass (NoMethodError)"

Immediately after I enter the quantity the programme throws this error after printing to the console the "----" under the list name. I've Googled it to death and updated my version of Ruby to ruby 1.9.3p484 (2013-11-22 revision 43786) [i686-linux]. Cannot resolve. Any help appreciated!

Code snippet... def print_list(list) puts "List: #{list['name']}" puts "----"

list["items"].each do |item| puts "Item: " + item['name'] puts "Quantity: " + item['quantity'].to_s puts "---" end end

David O' Rojo
David O' Rojo
11,051 Points
David O' Rojo
David O' Rojo
11,051 Points

Just to clarify your code:

def print_list(list)
  puts "List: #{list['name']}"
  puts "----"

  list["items"].each do |item|
    puts "Item: " + item['name']
    puts "Quantity: " + item['quantity'].to_s
    puts "---"
  end
end

You can use Markdown to give format to snippets.

David O' Rojo
David O' Rojo
11,051 Points
David O' Rojo
David O' Rojo
11,051 Points

Note: Moved this as a comment to your question as it is not the answer.

Checking your code, your function works just fine, so maybe your problem is at the definition of the collection:

def print_list(list)
  puts "List: #{list['name']}"
  puts "----"

  list["items"].each do |item|
    puts "Item: " + item['name']
    puts "Quantity: " + item['quantity'].to_s
    puts "---"
  end
end

grocery_list = {
  'name' => 'groceries',
  'items' => [
    { 'name' => 'milk', 'quantity' => 6  },
    { 'name' => 'eggs', 'quantity' => 12 },
  ]
}

print_list(grocery_list)

# List: groceries
# ----
# Item: milk
# Quantity: 6
# ---
# Item: eggs
# Quantity: 12
# ---

2 Answers

David O' Rojo
David O' Rojo
11,051 Points
David O' Rojo
David O' Rojo
11,051 Points

No offence intended, but you need to learn to present your code in a way that is easy to read, as it will help you and other programmers that read and debug the code. With Markdown is pretty easy to show coloured code in this forums.

Here is what your code looks like:

def create_list
  print "What is the list named? "
  name = gets.chomp

  hash = { "name" => name, "items" => Array.new }
  return hash
end

def add_list_item
  print "What is the item called? "
  item_name = gets.chomp

  print "How many of item? "
  qty = gets.chomp.to_i

  hash = { "name" => item_name, "qty" => qty }  # first error
  return hash
end

def print_list(list)
  puts "List: #{list['name']}"
  puts "----"

  list["items"].each do |item|
    puts "Item: " + item['name']
    puts "Quantity: " + item['quantity'].to_s # first error
    puts "---"
  end
end

def print_list(list)
  puts "List: #{list['name']}"
  puts "----"

  list["items"].each do |item|
    puts "Item: " + item['name']
    puts "Quantity: " + item['quantity'].to_s
    puts "---"
  end
end

list = create_list()
puts list.inspect
list['items'].push(add_list_item())

puts list.inspect
print_list('list') # second error

You have two errors there:

  • At add_list_item you're defining a key with the name of qty while in print_list you're referencing the same key as quantity.
  • When calling print_list at the end of the code, you're passing in a String instead of a Hash.
darrell mayson
darrell mayson
5,215 Points
darrell mayson
darrell mayson
5,215 Points

Thanks for your reply David. Yeah probably should have included full listing. Sorry it's not formatted but TBH learning a new syntax to post code for a language I'm learning may break me ><

def create_list print "What is the list named? " name = gets.chomp #chomp removes trailing white space hash = {"name" => name, "items" => Array.new} #eg., name='Groceries', items = [] return hash end

def add_list_item #returns: key/value hash # what will the item appear as in your list?
print "What is the item called? " item_name = gets.chomp

# what quantity of 'item' do you want?
print "How many of item? "
qty = gets.chomp.to_i # convert input from string to integer
hash = {"name" => item_name, "qty" => qty}
return hash

end

def print_list(list) puts "List: #{list['name']}" puts "----" list["items"].each do |item| puts "Item: " + item['name'] puts "Quantity: " + item['quantity'].to_s puts "---" end end

list = create_list() puts list.inspect list['items'].push(add_list_item()) # use 'push' method to insert new value into 'items' array.

puts list.inspect print_list('list')