Learning From Other Languages - Immutability

So many talks are about learning new languages and technology, but what can we bring back from those into Ruby...

Transcript

1. Learning from other languages Immutability
5. Immutability In object-oriented and functional programming, an immutable object is an object whose state cannot be modified after it is created.
6. Mutability This is in contrast to a mutable object, which can be modified after it is created.
7. Why is immutability good?
8. Why is immutability good? → Inherently thread safe
9. Why is immutability good? → Inherently thread safe → More memory efficient
10. Why is immutability good? → Inherently thread safe → More memory efficient → No side effects
11. Side effects?
12. Side effects? In medicine, a side effect is an effect, whether therapeutic or adverse, that is secondary to the one intended;
13. Side effects? In computer science a side effect is when a function or expression modifies some state outside its scope.
14. Side effects? a = "string" def some_method(takes_a_string) takes_a_string.upcase! end some_method(a)
15. Side effects? a = "string" def some_method(takes_a_string) takes_a_string.upcase! end some_method(a) puts a # => "STRING"
16. Side effects? heros = {turtle: "Michaelenglo"} def mutate(hash) hash[:turtle] = "Rafael" end mutate heros # => "Rafael" heros # => {:turtle=>"Rafael"}
17. Side effects? my.contacts << Person.new # => [#<Person>, #<Person>]
19. Immutability in other languages Elixir - everything is immutable.
20. Immutability in other languages Ada, C#, C++, Java, Perl, Python, JavaScript, Racket, Scala
21. Immutability in Ruby
22. Immutability in Ruby → Frozen objects
23. Immutability in Ruby "my_string".freeze {a: :hash}.freeze any_object.freeze
24. Immutability in Ruby mutate("my_string".freeze) # => RuntimeError: can't modify frozen String {a: :hash}.freeze # => RuntimeError: can't modify frozen Hash any_object.freeze # => RuntimeError: can't modify frozen <Object>
25. Immutability in Ruby → Frozen objects → Primitives such as numbers and symbols
26. Immutability in Ruby 6 += 2 # SyntaxError: (irb):9: syntax error, # unexpected tOP_ASGN, expecting end-of-input
27. Immutability in Ruby → Frozen objects → Primitives such as numbers and symbols → String literals from Ruby 2.3, optionally
28. Frozen string ruby --enable-frozen-string-literal # frozen_string_literal: true
29. Frozen string # frozen_string_literal: true "Hello".upcase! `upcase!': can't modify frozen String (RuntimeError) x = String.new('Hello') x.upcase! puts x #=> 'HELLO'
30. Immutability in Ruby → Libararies such as: → ice_nine (deep freezing objects) → values immutable structs → immutable-ruby immutable enumerables
31. Conclusion
32. Conclusion - Benefits → Immutability helps with thread safety → Immutability can save memory usage → Immutability has the potential for cleaner, side effect free code.
33. Conclusion - Drawbacks → In some cases mutability is more performant (e.g. RSpec mutates strings to avoid allocations)
34. Thanks @jonrowe