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.

Teacher's Notes
Video Transcript
Downloads

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

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

You need to sign up for Treehouse in order to download course files.

Ruby Collections

Build a Grocery List Program: Part 2

Code Samples

Sign in