Ruby Koans

This is my attempt to solve the Ruby Koans

Ruby version: 3.0.0

What I've Learned

• Basic TDD
  - Red, Green, Refactor
  - asert, asert_equal methods (File: about_asserts.rb line 19-34)

• Boolean:
  - false and nil is treated as false
  - Everything esle is treated as true. Example: 0, "", [], {}

• String:
  - Create string using single quotes, double quotes, flexible quotes, HERE docs.
  - Using backslash (\) for special characters (escape character)
  - Difference bettween flexible quotes and HERE docs (File: about_strings.rb line 38-56)
  - Prefer the shovel operator (>>) to the plus equal operator (+=) when concatenate strings (File about_strings.rb line 71-105)
  - String interpolation: "After 2 is #{2+1}"
  - Double quotes strings support string interpolation and all escape characters (ie: \n), single quotes strings don't
  - How to split and join strings
  - Strings are unique objects (2 variables with the same string value have different object id)

• Symbol:
  - Symbols can be compared
  - Identical symbols are the same object
  - String to Symbol: "cat".to_sym
  - Symbol to String: :cat.to_s
  - Symbol can have space between: :"cats and dogs"
  - Symbol interpolation is supported: :"cats #{value} dogs
  - Symbol doesn't have String methods
  - It's not a good idea to dynamically create a lot of symbols

• Array:
  - Interesting read about splat operator

• Object:
  - Everything is object
  - Every object have an unique object ID

• Hash:
  - hash[:doesnt_exist_key] return nil
hash.fetch(:doesnt_exist_key) throw KeyError exception
  - Hash is unordered
  - Hash default value is the same object h = Hash.new([]). To prevent this, use:
  - Hash default value with block: h = Hash.new {|hash, key| hash[key] = []}

• Method:
  - Method with default value for arguments: method_with_defaults(a, b=:default_value)
  - Method with variable arguments: method_with_var_args(*args)
  - Can't call private methods with an explicit receiver: self.private_method will raise NoMethodError exception
  - Keword arguments:
  method_with_keyword_arguments(one: 1, two: 'two')