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Build a Grocery List Program: Part 3

3:47 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 to output our list for us.

Code Samples

At the end of the video, your code should look like this:

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

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)

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    Okay, so when we last left off, 0:00
    we have added onto our shopping list after calling the add_list_item method. 0:02
    And that put list items into an array of hashes. 0:08
    So now that we have all of this done, let's go ahead and print out our list. 0:14
    And we'll create a new method to do that. 0:20
    So what I'm gonna do is click up in here and create a method called print_list. 0:24
    And we'll pass in as an argument the list that we want to print. 0:31
    So we know that our list has a name. 0:37
    So let's go ahead and print that out as the first item here. 0:42
    Now we do that by using string interpolation. 0:47
    Now we know that the list name is a string. 0:51
    And we access the value of that by calling list['name']. 0:54
    Since it's a string, string interpolation will work just the same. 1:01
    It's just like calling any other variable. 1:06
    Now, let's go ahead and create a line. 1:10
    That'll just be four dashes. 1:14
    Now what we want to do is print out the items in the list. 1:16
    Now we know that the list items is an array containing hashes. 1:21
    What we can do is use a method called each. 1:27
    We'll get into this method a little bit more in an upcoming course, 1:31
    but for right now, we'll just follow along. 1:34
    So we call the method each. 1:40
    Now when we call the method each, we use this new piece of Ruby syntax called 1:42
    a block, and then pass in an argument. 1:46
    Blocks are written by typing either curly braces or the words do and end. 1:54
    So what this is going to do is take each item in this array of list items and 2:01
    assign it to a variable called item. 2:09
    And now, we can print out the item name and the item quantity. 2:13
    Now remember the list items array is an array of hashes. 2:20
    So let's go ahead and 2:25
    print out the item['name'] because we want to know what the name is of the item. 2:27
    And we'll also print out quantity and the item's quantity. 2:34
    And then we'll print out another separator. 2:43
    Okay. 2:47
    Now that we have this, let's go ahead and call print_list and 2:48
    send in our shopping list. 2:52
    Let's run this and see what happens. 2:56
    The list name is Groceries, that item that we're adding is Milk, and 2:58
    we're adding one thing of milk. 3:03
    Oh, it looks like we have an error on line 26. 3:07
    And the error is, no implicit conversion of fixnum into String. 3:13
    So what we have to do is tell Ruby that we want this number to be a string. 3:19
    And we use the to_s method to do that. 3:25
    Let me clear my screen here. 3:27
    And we'll run this again and see what happens. 3:30
    Now we're going to add Milk and one thing of Milk. 3:34
    And now here is our grocery list. 3:38
    Alright, that looks good, but 3:42
    we're going to clean this up a little bit more in the next video. 3:44

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