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Build a Grocery List Program: Part 2

3:58 with Jason Seifer

Now that we know how to use arrays and hashes, we're going to build a small program that makes a grocery list for us. In this video, we'll modify our program make use of the methods we've written.

Code Samples

Here's what our code looks like now:

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

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    So when we just left off we had created a shopping list and 0:00
    printed out the contents. 0:03
    Now let's go ahead and add on to this and add an item to this list. 0:05
    So let's go ahead and call add_list_item dot inspect, and 0:11
    what that's gonna do is the call the add_list_item method and 0:15
    then we're just gonna see what the output is first. 0:20
    So we click down into the console and type ruby shopping_list.rb. 0:26
    The list name is "Groceries", and we don't have any items, so let's go ahead and 0:30
    add an item. 0:34
    And the item is Milk. 0:35
    Uh-oh. 0:38
    Undefined local variable or method name for main object. 0:39
    That's because we spelled it wrong. 0:44
    Our program freaked out a little bit, and that's okay. 0:47
    It exited, but nothing catastrophic happened. 0:51
    So let's go ahead and clear the screen, and run that again. 0:53
    And actually, let's put a space here, format that just a little bit better. 0:56
    List name is "Groceries", and go ahead and add "Milk" to our grocery list. 1:01
    And we can see that we return a new hash with the key of "name", 1:06
    and the value of Milk. 1:12
    And that's okay, but what I think I would like to do is also get the quantity back. 1:15
    So let's go ahead and ask how much. 1:22
    And we'll get from standard input again, and 1:28
    then call to_i on that, which will turn it into a number. 1:32
    And now we'll put that into the hash. 1:40
    Now let's go ahead and run this again and see what happens. 1:44
    List name is "Groceries". 1:48
    Item is "Milk". 1:51
    And I only want one. 1:53
    Now we can see that this add_list_item method is returning a hash with two keys, 1:56
    "name" and "quantity". 2:01
    Now let's go ahead and take a look at our list and see how it looks. 2:04
    Gonna clear my screen here and run the program again. 2:10
    So here is the item that we're returning, but 2:19
    it's not being added to our list of items inside of the hash. 2:22
    So let's go ahead and fix that. 2:29
    What we're gonna do is use the push method and the reason is "items" is an array. 2:32
    So let's go ahead and type list.push, and 2:40
    then the argument that we're adding to push is all_list_item. 2:44
    Now, we can print out the contents of the list again. 2:54
    Let me clear my screen here and run it again. 3:01
    Okay, we've got our grocery list created, "Milk", and we only need one. 3:05
    Uh-oh, undefined method push for this hash. 3:12
    Now what could that be? 3:17
    Well, we're not pushing onto the list hash. 3:20
    We're pushing onto the list items inside of the hash. 3:24
    Now let's clear this and run it again. 3:31
    Okay. 3:38
    Now this is what our grocery list looks like. 3:40
    It's a hash with two keys, "name" which is "Groceries", 3:43
    "items", which is an array, which contains a hash. 3:49
    In our next video we're going to format this. 3:55

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