Working with Hashes (1)

Before you get started, make sure you have your text editor and terminal open, and you have navigated to your exercises directory in the terminal. E.g. cd ~/ruby-for-beginners/exercises.

Exercise 4.1

Make a new file hashes_1-1.rb, and fill in the following line:

dictionary = { :one => 'uno', :two => 'dos', :three => 'tres' }
# your code goes here

So that it prints out dos.

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Exercise 4.2

Make a new file hashes_1-2.rb, and fill in the following line:

dictionary = { :one => 'uno', :two => 'dos', :three => 'tres' }
# your code goes here
puts dictionary[:four]

So that it prints out cuatro.

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Exercise 4.3

Copy that file to a new file cp hashes_1-2.rb hashes_1-3.rb, and change your code so that it prints out the following.

Cuatro

There’s a method that upcases the first letter of a string. Find it by googling for “ruby string upcase first letter”.

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Exercise 4.4

There is a method on hashes that allows to check if a certain key is defined on the hash. Find that method by googling for “ruby hash key defined”.

Try this method in irb by creating a hash like the one above, calling the method and passing keys like :one, :two, :four, and :ten.

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Exercise 4.5

There is a method on hashes that flips keys and values. Find that method on the Ruby documentation about hashes

Make a new file hashes_1-5.rb, and fill in the following line using that method:

dictionary = { :one => 'uno', :two => 'dos', :three => 'tres' }
# your code goes here

This should then output:

{ 'uno' => :one, 'dos' => :two, 'tres' => :three }

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