Pattern match samples

assert.rb

# inspired by https://qiita.com/kentaro/items/477c92a57c8aaf694251

user = {
  id: 123_456,
  name: "ksss",
  profile: {
    real_name: "栗原勇樹",
    image: {
      original: "...",
      thumbnail: "...",
    }
  }
}

def test_user
  user => { id: _, name: "ksss", profile: profile }
  profile => { real_name: "栗原勇樹", image: image }
  image => { original: _, thumbnail: _ }
end

core-ext.rb

def tuplize
  [:ok, yield]
rescue => err
  [:error, err]
end

# NoMatchingPatternError
case tuplize { File.open("./notexists.txt") }
in [:ok, file]
  begin
    # file.read
  ensure
    file.close
  end
end

case tuplize { File.open("./notexists.txt") }
in [:ok, file]
  begin
    # file.read
  ensure
    file.close
  end
in [:error, error]
  # error handling
  pp error
end

fizzbuzz.rb

def fizzbuzz(num)
  case [num % 3, num % 5]
  in [0, 0]
    puts 'FizzBuzz'
  in [0, _]
    puts 'Fizz'
  in [_, 0]
    puts 'Buzz'
  else
    puts num
  end
end

(1..20).map(&method(:fizzbuzz))

keyword-arguments.rb

def keyword(foo:, bar:, baz:)
  p foo
  p bar
  p baz
end

[{foo: 1, bar: 2, baz: 3}, {foo: 10, bar: 20, baz: 30}].each do |obj|
  keyword(**obj)
end

# 1
# 2
# 3
# 10
# 20
# 30

overload.rb

class Overload
  def method_missing(name, *args)
    case [name, args]
    in [:hello, []]
      puts "hello"
    in [:hello, [a]]
      puts "hello #{a}"
    in [:hello, [a, Integer => i]]
      puts("hello #{a}!" * i)
    end
  end
end

o = Overload.new

o.hello #=> hello
o.hello('ksss') #=> hello ksss
o.hello('ksss', 3) #=> hello ksss!hello ksss!hello ksss!
o.hello('ksss', 'yo') #=> in `method_missing': [:hello, ["ksss", "yo"]] (NoMatchingPatternError)

rescue.rb

begin
  # I do not know what will happen...
  raise [Errno::ENOENT, ZeroDivisionError, KeyError].sample
rescue Errno::ENOENT => err
  pp err
rescue ZeroDivisionError => err
  pp err
rescue KeyError => err
  pp err
end