##Objectives
- Iterate through a nested hash
- Modify the correct element in a nested hash
So much of what we do in programming involves storing data in hashes. Often the hashes that we will encounter will have more than one level. As we get into the web, this will become abundantly clear. To build programs in the future, we'll absolutely need to get comfortable working with hashes. Let's get started!
##Code Along Exercise
Fork and clone this lab. You'll be coding your solution in lib/contacts.rb
. You'll be manipulating the following hash:
contacts = {
"Jon Snow" => {
name: "Jon",
email: "[email protected]",
favorite_ice_cream_flavors: ["chocolate", "vanilla"]
},
"Freddy Mercury" => {
name: "Freddy",
email: "[email protected]",
favorite_ice_cream_flavors: ["strawberry", "cookie dough", "mint chip"]
}
}
Your good buddy Freddy Mercury has recently developed a strawberry allergy! You need to delete "strawberry"
from his list of favorite ice cream flavors in the remove_strawberry
method.
Iterate over the contacts
hash and when you reach the key :favorite_ice_cream_flavors
, remove "strawberry"
from the array of Freddy's favorite ice cream flavors.
There are at least two ways you can accomplish this, and for this codealong, we'll work with the second way.
- You can directly iterate over the hash that is the value of the
"Freddy Mercury"
key by calling an enumerator method incontacts["Freddy Mercury"]
. - You can iterate through the hash and, when you reach the appropriate level, check to see if the key
==
("is equal to"):favorite_ice_cream_flavors
. If it does, check to see if that array contains"strawberry"
. If it does, then delete it from the array.
###Step 1. Iterate over the first level
Inside the remove_strawberry
method, let's take our first dive into the contacts hash. Then we'll use binding.pry
to see where we are.
We are going to first iterate over the top level of the hash where the keys should be the person and the values should be a hash of details about the person.
Note on variable naming: This process will be remarkably easier if you name your variables to accurately reflect the data they represent. For now, when the value we're iterating over is another hash, we will explicitly add a _hash
to the end of the variable name (E.G. contact_details_hash
below).
contacts.each do |person, contact_details_hash|
binding.pry
end
In the terminal, let's hit the pry
by running ruby bin/contacts
, and check that our defined variables (person
and contact_details_hash
) match our expectations.
> person
=> "Jon Snow"
> contact_details_hash
=> {:name=>"Jon", :email=>"[email protected]", :favorite_ice_cream_flavors=>["chocolate", "vanilla"]}
Excellent! They do.
###Step 2. Iterate over the second level
contacts.each do |person, contact_details_hash|
contact_details_hash.each do |attribute, data|
binding.pry
end
end
Again, let's jump into our binding.pry
. You should see:
> attribute
=> :name
> data
=> "Jon"
###Step 3. Locate the element we're looking for
contacts.each do |person, contact_details_hash|
contact_details_hash.each do |attribute, data|
if attribute == :favorite_ice_cream_flavors
binding.pry
end
end
end
What is data
when we hit the binding? If it's unclear, let's go into our binding.
###Step 4. Update the hash
Lastly, we will use delete_if
to iterate through the ice cream array and remove any element that matches "strawberry". delete_if
will iterate through the hash and delete the key/value pair if the block returns true
. Learn more about it in the ruby docs..
contacts.each do |person, contact_details_hash|
contact_details_hash.each do |attribute, data|
if attribute == :favorite_ice_cream_flavors
data.delete_if {|ice_cream| ice_cream == "strawberry"}
end
end
end
def remove_strawberry(contacts)
contacts.each do |person, contact_details_hash|
contact_details_hash.each do |attribute, data|
if attribute == :favorite_ice_cream_flavors
data.delete_if {|ice_cream| ice_cream == "strawberry"}
end
end
end
end
Congrats! You made it. Test that your method works by running ruby bin/contacts
in the terminal. It should output the hash without strawberry ice cream. Also, be sure to run the specs to make sure they pass.
View Code Along: Manipulating Nested Hashes on Learn.co and start learning to code for free.