A PR Has Been Submitted

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1. @PauloAncheta
8. A Pull Request Has Been Submitted
10. 1. Remove @instance_variables
11. # test.rb puts @car puts car $ ruby test.rb NameError: undefined local variable or method `car` for main:Object
12. # test.rb puts “#{@car} #{car}” $ ruby test.rb NameError: undefined local variable or method `car` for main:Object
13. # test.rb puts @car.class puts “This car is #{@car}” $ ruby test.rb NilClass This car is
15. # test.rb puts “This car is #{@car.capitalize}” $ ruby test.rb NoMethodError: undefined method `capitalize’ for nil:NilClass
16. 2. Avoid Hash[key]
17. Hash[ ]
20. # test.rb hash = {a: {b: {c: {d: “ ”}}}} puts hash[:a][:b][:c][:d] $ ruby test.rb
21. # test.rb hash = {a: {b: {c: {z: “ ”}}}} puts hash[:a][:b][:c][:d] $ ruby test.rb # nil
22. # test.rb hash = {a: {b: {z: {d: “ ”}}}} puts hash[:a][:b][:c][:d] $ ruby test.rb NoMethodError: undefined method `[]' for nil:NilClass
23. # test.rb hash = {a: {b: {c: {d: “ ”}}}} puts hash.dig(:a, :b, :c, :d) $ ruby test.rb
24. # test.rb hash = {a: {y: {c: {d: “ ”}}}} puts hash.dig(:a, :b, :c, :d) $ ruby test.rb # empty output
25. hash = {a: {y: {c: {d: “ ”}}}} puts hash.fetch(:a) .fetch(:b) .fetch(:c) .fetch(:d) $ ruby test.rb KeyError: key not found: :b # test.rb
27. 3. (rails) Use ! more
28. 3. (rails) Use ! more
30. $ bin/rails c irb(main):1:0> Account.first.update(name: “this is too long”) Account Load (0.4ms) SELECT `accounts`.* FROM `accounts` ORDER BY `accounts`.`id` ASC LIMIT 1 (0.1ms) BEGIN Account Exists (0.2ms) SELECT 1 AS one FROM `accounts` WHERE (`accounts`.`token` = BINARY 'a6db14e97e1f9fe7' AND `accounts`.`id` != 1) LIMIT 1 (0.1ms) ROLLBACK false
31. $ bin/rails c irb(main):1:0> Account.first.update!(name: “this is too long”) Account Load (0.4ms) SELECT `accounts`.* FROM `accounts` ORDER BY `accounts`.`id` ASC LIMIT 1 (0.1ms) BEGIN Account Exists (0.2ms) SELECT 1 AS one FROM `accounts` WHERE (`accounts`.`token` = BINARY 'a6db14e97e1f9fe7' AND `accounts`.`id` != 1) LIMIT 1 (0.1ms) ROLLBACK ActiveRecord::RecordInvalid: Validation failed: Name is too long (maximum is 20 characters) … … …
33. Conclusion