- 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!
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 set a conditional to iterate through the hash for
Freddy Mercuryonly; when you reach the appropriate level, check to see if the key==("is equal to"):favorite_ice_cream_flavors. If it is, check to see if the array of flavors contains"strawberry". If it does, then delete it from theArray.
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
endWe can enter the pry in one of two ways: by running learn test or by
running ruby lib/contacts.rb. We'll use learn test.
Let's run learn test in the terminal and, at the pry prompt, 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!
Type exit while in pry to continue. The pry should trigger a second time
because we have two contacts. You can verify that we're in the second loop
through our hash by checking the values of person and data at the pry
prompt.
Typing exit now will end the loop and exit pry since we've finished
iterating through our contacts. It will also display the results of the test,
which we haven't passed just yet.
contacts.each do |person, contact_details_hash|
if person == "Freddy Mercury"
contact_details_hash.each do |attribute, data|
binding.pry
end
end
endAgain, let's jump into our binding.pry using learn test. We can verify that
we've found the record for Freddy Mercury by checking the values of our
variables:
attribute
# => :name
data
# => "Freddy"Before we move on, you will need to exit pry again so you can see the results
of the new code we'll be writing in Step 3. We are now inside the loop through
the attributes. Because there are three of them, we will need to run exit
three times to finish the loop and exit pry. Alternatively, you can run
exit! or !!! at any time to exit out of pry entirely.
contacts.each do |person, contact_details_hash|
if person == "Freddy Mercury"
contact_details_hash.each do |attribute, data|
if attribute == :favorite_ice_cream_flavors
binding.pry
end
end
end
endThis time we are still iterating through the attributes but we've added a
conditional so the pry will only hit when the attribute is equal to
:favorite_ice_cream_flavors. If we check the value of data in our
binding, we should see the array containing Freddy's favorite flavors.
Lastly, we will use delete_if to iterate through the ice cream array and
remove any element that matches "strawberry". Recall that data is the array
containing Freddy's favorite ice cream flavors. delete_if will iterate through
the array, check each element to see if it is equal to "strawberry", 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|
if person == "Freddy Mercury"
contact_details_hash.each do |attribute, data|
if attribute == :favorite_ice_cream_flavors
data.delete_if {|ice_cream| ice_cream == "strawberry"}
end
end
end
endThe full method should now be:
def remove_strawberry(contacts)
contacts.each do |person, contact_details_hash|
if person == "Freddy Mercury"
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
endCongrats! 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.
React
Typescript
Django
Laravel
Facebook
Microsoft
Google
Alibaba
D3
Tencent