Exercism: Grade School (Ruby)

A presentation outlining my solution to the Exercism Grade School problem in Ruby (http://exercism.io/exercises/ruby/grade-school/readme).

Presented at the Ruby on Rails Oceania meetup on 12 June 2018.

Presentation slide deck markdown and speaker notes (useable in Deckset 2):
https://github.com/paulfioravanti/presentations/tree/master/exercism_ruby_grade_school

Transcript

1. Exercism: Grade School
3. School Roster !
4. School Roster
5. School Roster ! Add a student's name to the roster for a grade
6. School Roster ! Add a student's name to the roster for a grade ! Get a list of all students enrolled in a grade
7. School Roster ! Add a student's name to the roster for a grade ! Get a list of all students enrolled in a grade ! Get a sorted list of all students in all grades
8. ! Take 1
9. Create a School Roster class School def initialize @roster = [] end private attr_reader :roster end
10. A Roster is filled with Enrollments > @roster => [ { grade: 1, students: ["Paul", "RobC"] }, { grade: 2, students: ["Nick"]) }, { grade: 3, students: ["Cath", "RobH"]) } ]
11. Add Student Name to Roster
12. Add Student Name to Roster def add(name, grade) grade_enrollment = roster.find { |enrollment| enrollment[:grade] == grade } if grade_enrollment grade_enrollment[:students] << name else roster << { grade: grade, students: [name] } end end
13. Add Student Name to Roster def add(name, grade) grade_enrollment = roster.find { |enrollment| enrollment[:grade] == grade } if grade_enrollment grade_enrollment[:students] << name else roster << { grade: grade, students: [name] } end end
14. Add Student Name to Roster def add(name, grade) grade_enrollment = roster.find { |enrollment| enrollment[:grade] == grade } if grade_enrollment grade_enrollment[:students] << name else roster << { grade: grade, students: [name] } end end
15. Add Student Name to Roster def add(name, grade) grade_enrollment = roster.find { |enrollment| enrollment[:grade] == grade } if grade_enrollment grade_enrollment[:students] << name else roster << { grade: grade, students: [name] } end end
16. Add Student Name to Roster def add(name, grade) grade_enrollment = roster.find { |enrollment| enrollment[:grade] == grade } if grade_enrollment grade_enrollment[:students] << name else roster << { grade: grade, students: [name] } end end
17. Add Student Name to Roster def add(name, grade) grade_enrollment = roster.find { |enrollment| enrollment[:grade] == grade } if grade_enrollment grade_enrollment[:students] << name else roster << { grade: grade, students: [name] } end end
18. Add Student Name to Roster def add(name, grade) grade_enrollment = roster.find { |enrollment| enrollment[:grade] == grade } if grade_enrollment grade_enrollment[:students] << name else roster << { grade: grade, students: [name] } end end
19. Get list of students in a grade
20. Get list of students in a grade def students(grade) grade_enrollment = roster.find { |enrollment| enrollment[:grade] == grade } if grade_enrollment grade_enrollment[:students].sort else [] end end
21. Get list of students in a grade def students(grade) grade_enrollment = roster.find { |enrollment| enrollment[:grade] == grade } if grade_enrollment grade_enrollment[:students].sort else [] end end
22. Get list of students in a grade def students(grade) grade_enrollment = roster.find { |enrollment| enrollment[:grade] == grade } if grade_enrollment grade_enrollment[:students].sort else [] end end
23. Get list of students in a grade def students(grade) grade_enrollment = roster.find { |enrollment| enrollment[:grade] == grade } if grade_enrollment grade_enrollment[:students].sort else [] end end
24. Get list of students in a grade def students(grade) grade_enrollment = roster.find { |enrollment| enrollment[:grade] == grade } if grade_enrollment grade_enrollment[:students].sort else [] end end
25. Get list of students in a grade def students(grade) grade_enrollment = roster.find { |enrollment| enrollment[:grade] == grade } if grade_enrollment grade_enrollment[:students].sort else [] end end
26. Get sorted list of students in all grades
27. Get sorted list of students in all grades def students_by_grade roster .sort_by { |enrollment| enrollment[:grade] } .map do |enrollment| enrollment[:students] = enrollment[:students].sort enrollment end end
28. Get sorted list of students in all grades def students_by_grade roster .sort_by { |enrollment| enrollment[:grade] } .map do |enrollment| enrollment[:students] = enrollment[:students].sort enrollment end end
29. Get sorted list of students in all grades def students_by_grade roster .sort_by { |enrollment| enrollment[:grade] } .map do |enrollment| enrollment[:students] = enrollment[:students].sort enrollment end end
30. Get sorted list of students in all grades def students_by_grade roster .sort_by { |enrollment| enrollment[:grade] } .map do |enrollment| enrollment[:students] = enrollment[:students].sort enrollment end end
31. Get sorted list of students in all grades def students_by_grade roster .sort_by { |enrollment| enrollment[:grade] } .map do |enrollment| enrollment[:students] = enrollment[:students].sort enrollment end end
32. Get sorted list of students in all grades def students_by_grade roster .sort_by { |enrollment| enrollment[:grade] } .map do |enrollment| enrollment[:students] = enrollment[:students].sort enrollment end end
33. exercism submit grade_school.rb
34. Done!
35. Done?
36. What gives?
37. What gives? ! Methods are kind of long...
38. What gives? ! Methods are kind of long... ! Is the naming right...?
39. What gives? ! Methods are kind of long... ! Is the naming right...? ! There's code repe99on...
40. What gives? ! Methods are kind of long... ! Is the naming right...? ! There's code repe99on... ! Something doesn't feel right...
41. ! Take 2
42. Create a School Roster class School def initialize @roster = [] end private attr_reader :roster end
43. A Roster is filled with Enrollments > @roster => [ { grade: 1, students: ["Paul", "RobC"] }, { grade: 2, students: ["Nick"]) }, { grade: 3, students: ["Cath", "RobH"]) } ]
44. Simplify to a Hash of Enrollments > @enrollments => { 1 => ["Paul", "RobC"], 2 => ["Nick"], 3 => ["Cath", "RobH"] }
45. Create a Hash of Enrollments class School def initialize @enrollments = {} end private attr_reader :enrollments end
46. Add Student Name to Roster def add(name, grade) grade_enrollment = roster.find { |enrollment| enrollment[:grade] == grade } if grade_enrollment grade_enrollment[:students] << name else roster << { grade: grade, students: [name] } end end
47. Add Student Name to Roster def add(name, grade) grade_enrollment = roster.find { |enrollment| enrollment[:grade] == grade } if grade_enrollment grade_enrollment[:students] << name else roster << { grade: grade, students: [name] } end end
48. Add Student Name to Roster def add(name, grade) grade_enrollment = roster.find { |enrollment| enrollment[:grade] == grade } if grade_enrollment grade_enrollment[:students] << name else roster << { grade: grade, students: [name] } end end
49. Get list of students in a grade def students(grade) grade_enrollment = roster.find { |enrollment| enrollment[:grade] == grade } if grade_enrollment grade_enrollment[:students].sort else [] end end
50. Get list of students in a grade def students(grade) grade_enrollment = roster.find { |enrollment| enrollment[:grade] == grade } if grade_enrollment grade_enrollment[:students].sort else [] end end
51. Get list of students in a grade def students(grade) grade_enrollment = roster.find { |enrollment| enrollment[:grade] == grade } if grade_enrollment grade_enrollment[:students].sort else [] end end
52. Too much repetition
53. Create a Hash of Enrollments class School def initialize @enrollments = {} end private attr_reader :enrollments end
54. Create a Hash of Enrollments class School def initialize @enrollments = Hash.new { |hash, key| hash[key] = [] } end private attr_reader :enrollments end
55. Create a Hash of Enrollments class School def initialize @enrollments = Hash.new { |hash, key| hash[key] = [] } end private attr_reader :enrollments end
56. Add Student Name to Roster def add(name, grade) grade_enrollment = roster.find { |enrollment| enrollment[:grade] == grade } if grade_enrollment grade_enrollment[:students] << name else roster << { grade: grade, students: [name] } end end
57. Add Student Name to Enrollments def add(name, grade) enrollments[grade] << name end
58. Get list of students in a grade def students(grade) grade_enrollment = roster.find { |enrollment| enrollment[:grade] == grade } if grade_enrollment grade_enrollment[:students].sort else [] end end
59. Get list of students in a grade def students(grade) enrollments[grade].sort end
61. Get sorted list of students in all grades def students_by_grade roster .sort_by { |enrollment| enrollment[:grade] } .map do |enrollment| enrollment[:students] = enrollment[:students].sort enrollment end end
62. Get sorted list of students in all grades def students_by_grade enrollments.sort.map do |grade, students| { grade: grade, students: students.sort } end end
63. Get sorted list of students in all grades def students_by_grade enrollments.sort.map do |grade, students| { grade: grade, students: students.sort } end end
64. Get sorted list of students in all grades def students_by_grade enrollments.sort.map do |grade, students| { grade: grade, students: students.sort } end end
65. Get sorted list of students in all grades def students_by_grade enrollments.sort.map do |grade, students| { grade: grade, students: students.sort } end end
66. Get sorted list of students in all grades > school.students_by_grade => [ { grade: 1, students: ["Paul", "RobC"] }, { grade: 2, students: ["Nick"]) }, { grade: 3, students: ["Cath", "RobH"]) } ]
67. You'll rarely get it right the first time
68. Submit often, get feedback
69. Read other people's code
70. Refactor until you're happy
71. github.com/paulfioravanti/exercism
72. Thanks! @paulfioravanti