- 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: "jon_snow@thewall.we",
favorite_ice_cream_flavors: ["chocolate", "vanilla"]
},
"Freddy Mercury" => {
name: "Freddy",
email: "freddy@mercury.com",
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 Mercury
only 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 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
end
In the terminal, let's hit the pry
by running learn
, and check
that our defined variables (person
and contact_details_hash
) match our
expectations.
> person
=> "Jon Snow"
> contact_details_hash
=> {:name=>"Jon", :email=>"jon_snow@thewall.we", :favorite_ice_cream_flavors=>["chocolate", "vanilla"]}
Excellent! They do!
Type exit
while in pry to continue (a second pry
will trigger since we have
two contacts). Running learn
will also display a test, which we haven't
passed just yet.
You can also run ruby lib/contacts.rb
in the terminal - instead of displaying the
the test results, this will reach the binding.pry
.
contacts.each do |person, contact_details_hash|
if person == "Freddy Mercury"
contact_details_hash.each do |attribute, data|
binding.pry
end
end
end
Again, let's jump into our binding.pry
using learn
. You should see:
> attribute
=> :name
> data
=> "Jon"
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
end
What is data
when we hit the binding? If it's unclear, let's go into our
binding.
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|
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
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
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.