Covered In This Episode:
- What are Hashes?
- Hash Creation
- Hash Accessing
- Hash iteration
- Hash Methods
Transcript:
Hello Everybody and welcome to Programming With Ruby Episode 8,
Hashes. I’m Tyler,and this video is brought to you by, manwithcode.com
In this episode I will be telling you what hashes are, how you can
create them, access them, and iterate over them. Finally at the end I
will show you some useful methods that hashes have.
What Are Hashes?
Hashes are like arrays, which you learned about in the previous
episode. Except that they have no order, and instead of being accessed
by an index number, they are accessed by what is called a key (which
can be anything). That key points to a value, which is the actual data
inside the hash
Arrays are used for lists of data, where hashes are used to relate
data. I may have a hash where the keys are my friend’s names, and the
values are their birthdays.
Hash Creation
Similarly to how arrays are created with square brackets, hashes are
created with curly brackets:
my_hash = {}
Items are defined like this:
birthdays = {"Amy" => "May", "Dakota" => "January"}
Each key-value pair are separated by a comma, and their relation is
defined with =>
Accessing Hashes
You can access hashes in almost the same way you access arrays, except
by using the key value, instead of an index number:
brithdays["Amy"] #=> May
You can define new keys and values:
birthdays["Zack"] = "April"
Iterating Over Hashes
Hashes have an each method like arrays do:
my_hash = {"cat" => "hat", "dog" => "log"}
my_hash.each do |pair|
puts "Key: " + pair[0]
puts "Value: " + pair[1]
end
#=> Key: cat
#=> Value: hat
#=> Key: dog
#=> Value: log
They also have each_key and each_value which let you iterate over each
key or value in a similar way.
Useful Hash Methods
delete(key) deletes a key-value pair
empty? True or False if the hash is empty
keys returns the keys
values returns the values
size how many key-value pairs there are
That wraps it up for this episode!
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If you have any questions or comments leave a comment on this page or
email me at tyler@manwithcode.com
Thanks for watching, goodbye!