panpsychism/ruby_rails_sql_resources/morning_Ex/ruby_methods.md

SELECTED RUBY METHODS

Here are some exercises to become more acquainted with the following Ruby methods:

1. .each
2. .class
3. .select
4. .reject
5. .flatten
6. .permutation.to_a
7. .first
8. .last
9. .count
10. .reduce
11. .uniq
12. .shuffle
13. .each_slice
14. .sample
15. .each_cons

1

Given the following array

arr = [["Live", "Laugh", "Love"], {hello: 'hi back'}, false, 333.333, nil, nil, ["Joy", "Joke", "Jerk"]]

1. Use .each and .class to print the class of each array element to the console

2. Use .select and .class to return an array of only those elements whose class is Array. http://ruby-doc.org/core-2.3.0/Enumerable.html#method-i-select

3. Use .reject and .class to return an array of only those elements whose class is not Hash. http://ruby-doc.org/core-2.3.0/Enumerable.html#method-i-reject

4. Use .flatten on the result of your previous .select operation to flatten out the array

5. Use .permutation.to_a on the flattened result to return all possible permutations of all the items within the inner arrays.

6. Use .count to get the number of those permutations.

2

Given the following array

numbers = [4, 7, 8, 7, 9, 0, 4]

1. Use .permutation.to_a and .count to return a count of all permutations

2. .select only those permutations where the .first number is 7 and the .last number is also 7, and return a .count of those permutations.

3. Use .reduce to get the sum of the array.

4. Use .reduce to get the product of the array.

3

Given the following array

strings = ["Paloma", "Grits", "Ziti", "Carbohydrates", "Grits", "Corn", "Wizard_robe", "Ziti", "Corn", "Corn", "Maize"]

and the empty hash

hash = {}

1. Using .each and .uniq, populate the hash using the elements in the array as keys. Remember that keys must be unique, so don't include any double-ups. Set the values of those keys to "Fun" except for Maize, which is "Not Fun".

4

students =  [
							"Amber",
							"Nicole",
							"Christine",
							"Dan",
							"Ashleigh",
							"Jordan",
							"Alex",
							"Emily",
							"John",
							"Sharon",
							"Levi",
							"Pauline",
							"Masha",
							"Matt",
							"Andy",
							"Sammy",
							"Dominic",
							"Vincent",
							"Jesse",
							"Juan",
							"Josh",
							"Derek"
						];

1. Pretend that group projects are coming up again, and you have to split the class up into random groups of three. Use .shuffle and .each_slice to generate groups of three (there will be one remainder). http://ruby-doc.org/core-2.3.0/Enumerable.html#method-i-each_slice.

2. Use .sample to return a single random student to be taken to jail. http://ruby-doc.org/core-2.1.4/Array.html#method-i-sample

5. Make your own problem

Look into the Ruby method .each_cons, http://ruby-doc.org/core-2.3.0/Enumerable.html#method-i-each_cons

Make your own problem where the answer should use .each_cons.