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Ruby Ruby Collections Build a Grocery List Program Build a Grocery List Program: Part 2

Posted by Oğulcan Girginc
Oğulcan Girginc
24,848 Points

undefined method `push' for nil:NilClass (NoMethod Error)

def create_list
  print "What is the list name?: "
  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 much?: "
  quantity = gets.chomp.to_i

  hash = { name: item_name, quantity: quantity }
  return hash
end

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

puts list.inspect

When I use 

hash = { name: name, items: Array.new }

instead of 

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

I am getting an error. Does anyone know why?

3 Answers

Martin Cornejo Saavedra
Martin Cornejo Saavedra
18,132 Points

The error is here:

list['items'].push(add_list_item())

#Should be
list[:items].push(add_list_item())
Oğulcan Girginc
Oğulcan Girginc
24,848 Points

So if I want to use

name: item_name

I always need to use

list[:name]

Am I correct?

Alan Matthews
Alan Matthews
10,161 Points
Alan Matthews
Alan Matthews
10,161 Points

I believe it would depend upon on what the hash key is. In your above code you made hash = { name: name, items: Array.new } a hash, where items: is a symbol that is the key and a new Array is the value. Newer versions of Ruby are deprecating the old hash syntax in favor of using symbols as keys. Docs here: http://rubylearning.com/satishtalim/ruby_hashes.html

If you had made items a string in the create_list method, then your original syntax list['items'].push(add_list_item()) should work if I'm not mistaken.

Alan Matthews
Alan Matthews
10,161 Points
Alan Matthews
Alan Matthews
10,161 Points

You also don't need to specifically return anything in a Ruby method. It will always return the last expression evaluated.