Week 2 Diagnostic

week_2_diag.md

Week 2 Diagnostic

This exercise is intended to help you assess your progress with the concepts and techniques we've covered during the week.

For these questions, write a short snippet of code that meets the requirement. In cases where the question mentions a "given" data value, use the variable given to refer to it (instead of re-writing the information).

Use single (`) and triple backticks (```) to container code snippets.

1. Define a class called PizzaOven which has a method cook_pizza which returns the string "mmm 'za".

class PizaOven
	def cook_piza
	  "mmm `za"
	end
end

2. Define a class called Student which is instantiated with a "name" value and which has a method name that returns this value

class Student
  attr_reader :name

  def initialize
    @name = "name"
  end
end

3. Given an array of the numbers [1,2,3,4,5], how would you create a new array of all elements doubled? How would you return an array of all odd elements?

arr =[1,2,3,4,5]
arr.each{ |element| 2 *= element }

arr.each{ |el| el.odd? }

4. Give the command to create a new Git repository in a directory on your machine

git init

Pizza

5. Given a hypothetical Pizza class which has an instance method is_tasty? that always returns true, write a simple Minitest test that tests this behavior.

def test_does_is_tasty_return_true
  p = Pizza.new

  assert p.is_tasty?
end

6. Suppose the Pizza class also has a method style which randomly returns one of: "supreme", "mediterranean", or "cheese". Write a test that confirms that the returned pizza style is within this list.

def test_supreme_returns_one_of_three
  p = Pizza.new
  type = p.style

  assert_equal type, p.style
end

6. Give the Git commands needed to stage and then commit a set of changes to a file

git add file_name
git push -m "test message"

Student

7. Define a Student class which, when created, has an attitude attribute. attitude should start out with the value "cheerful", and the Student class should provide a "reader" method that allows us to access the value of its attitude.

class Student
  attr_reader :attitude

  def initialize(attitude="cheerful")
    @attitude = attitude
  end
end

8. Additionally, add an assign_homework method to Student. When assigned_homework is invoked, if the student's attitude is "cheerful", it should become "dubious". If the value is currently "dubious" it should become "perturbed". If the value is currently "perturbed", it should become "dazed". Assigning homework to a "dazed" student has no effect.

class Student
  ...
  def assign_homework
    if attitude == "cheerful"
      @attitude = "dubious"
    elsif attitude == "dubious"
      @attitude = "perturbed"
    elsif attitude == "perturbed"
      @attitude = "dazed"
    end
  end
end

9. Building on the Student class from the previous example, update the assign_homework method to accept an argument. The argument will be a String containing a short description of the assignment. For example we might use it like this:

s = Student.new
s.assign_homework("Write a linked list")

  attr_accessor :attitude, :assignemnts

  def initialize(attitude="cheerful")
    @attitude = attitude
    @assignments = []
  end

  def assign_homework(assignment)
    ..
    @assignments << assignment
  end
end

Then, add an assignments method to Student. assignments should return a list of all the assignments that have been given, separated by a comma and a space. For example:

s = Student.new
s.attitude
=> "cheerful"
s.assign_homework("write a linked list")
s.attitude
=> "dubious"
s.assign_homework("write a BST")
s.attitude
=> "perturbed"
s.assignments
=> "write a linked list, write a BST"

..
  def assignments
      return "#{@assignments[0], #{assignments[1]} }
  end
..

10. Given an array of 3 Student instances, generate a new string of all of their assignments

For example:

s1 = Student.new
s2 = Student.new
s3 = Student.new

s1.assign_homework("linked list")
s1.assign_homework("sorting algos")

s2.assign_homework("write a c compiler")
s2.assign_homework("write a pacman game")

s3.assign_homework("headcount")
s3.assign_homework("sales engine")

students = [s1,s2,s3]

# YOUR CODE HERE
final = ''

students.each do |student|
  final += "student.assignments.to_s + ', '"
  final
end

=> "linked list, sorting algos, write a c compiler, write a pacman game, headcount, sales engine"

11. What does the following code output?

def print_variables(x)
  puts "x: #{x}"
  puts "b: #{b}"
end

def b
  12
end

a = 4
print_variables(a)

x: 4
b: 12

12. Working with files: given a text file located at "~/Documents/pizza.txt", write code to read the file from the filesystem and print each line one at a time.

file = File.open("~/Documents/pizza.txt", "r")
puts file.read.split('\n')

13. Writing Files: given a text file located at "~/Documents/pizza.txt", write code to read the file from the filesystem, then write a new file at "~/Documents/line_count.txt" containing the number of lines in the original file.

file = File.open("~/Documents/pizza.txt", "r")
File.write("~/Documents/line_count.txt", file.read.to_s.length)

14. Imagine a simple ruby class designed to represent a Corgi dog. Write a test for each of the following features:

• A Corgi can be created with no arguments
• A Corgi can be assigned a name
• A Corgi can be asked for its name
• A Corgi can be asked for its posture, which should default to "standing"
• A Corgi can be asked to lie down, which should change its posture to "laying"

def test_corgi_is_created
  corgi = Corgi.new

  assert_instance_of Corgi, corgi
end

def test_corgi_with_name
  corgi = Corgi.new("roofus")

  assert_instance_of Corgi, corgi
end

def test_corgi_name_returns_name
  corgi = Corgi.new
  corgi.name = "roofus"

  assert_equal "roofus", corgi.name
end

def test_posture_returns_default_standing
  corgi = Corgi.new

  assert_equal "standing", corgi.posture
end

def test_corgi_lies_down
  corgi = Corgi.new
  corgi.lie_down

  assert_equal "laying", corgi.posture
end