• Access specific data in Hashes
• Modifying data in Hashes
• Perform operations on Hashes guided by tests

We've discussed a few different ways that Hashes can be created and how useful they are in storing and retrieving associated data with ease. In this lesson, we're going to practice accessing and modifying Hashes.

We're going to host a dinner party! We have a list of nutritious ingredients we will be using to make dinner, but we want to prepare separate dishes for guests with dietary restrictions: vegetarian, ketogenic, and mediterranean.

Here is our full list of ingredients:

shopping_list = {
    :sweets => ["soda", "candy", "potato chips"],
    :protein => {
        :meat => ["chicken", "fish", "steak"],
        :other => ["eggs", "nuts","beans"]
    },
    :dairy => ["milk", "yogurt", "cheese"],
    :fruits => ["bananas", "oranges", "apples", "grapes"],
    :vegetables => ["cabbage", "broccoli", "tomatoes", "carrots"],
    :grains => ["crackers", "rice", "bread", "pasta", "cereal"]
}

We will have to make sure only some of these items are used in our special dishes. Since our recipes will require some attention to detail, we're going to write methods that filter out the appropriate content.

We don't want to modify our original list, instead creating new Hashes to represent the 3 separate ingredients lists for our guests with dietary restrictions.

In lib/hash_drills.rb, we've got a method, shopping_list, that returns a Hash of our main shopping list. Your first task is to write three methods that return Hashes with only the appropriate keys from our shopping_list Hash:

vegetarian_ingredients: Vegetarian dishes cannot include meat or fish. While some vegetarians are okay with eggs, leave them off as well.

ketogenic_ingredients: Ketogenic dishes have very few carbs and sugars, and cannot include grains, fruits, or sweets. Cheese is great for keto, but not milk or yogurt. Also, leave out the beans.

mediterranean_ingredients: For mediterranean dishes, we can only include chicken, fish, nuts, yogurt, cheese, fruits, vegetables, and grains.

After writing each method, run learn to confirm your solutions before continuing.

It turns out you've got a last minute addition to your guest list: your vegan friend is coming as well! We'll need to prepare a vegan_ingredients list. However, vegan diets are similar to vegetarian diets, so rather than write a method that filters from from our shopping_list, let's use use the Hash returned by vegetarian_ingredients, remove all dairy items from it, and return this updated Hash.

You found a great recipe online for sweet and salty party nuts, and are eager to try it out on your guests. However, a dear friend RSVP'd saying she may or may not be able to make it. She has a severe nut allergy, and if she is able to come, you will need to modify all of your ingredients lists to make sure there are no nuts in anything.

Write a method remove_allergens that takes in any one of our ingredients Hashes as an argument, and returns a new Hash with nuts removed.

There are so many things to do to get ready for our party. With a little help from Ruby Hashes, though, we've got our lists of ingredients and can start preparing our menu! The guests will be elated. Bon appetit!

• Hashes