A Dog is not a Dog

Switch statements and equivalence gotchas in Ruby

Transcript

1. A Dog is not a Dog equivalence gotchas in Ruby jcohenho.github.io
2. case @activity.class when UserLoggedInActivity “User has logged in.” when UserMessagedActivity “User sent a message.” when UserLoggedOutActivity “User logged out.” else “Why isn’t this working” end
3. case @activity.class when UserLoggedInActivity “User has logged in.” when UserMessagedActivity “User sent a message.” when UserLoggedOutActivity “User logged out.” else “Why isn’t this working” end => “Why isn’t this working”
4. case @activity.class when UserLoggedInActivity “User has logged in.” when UserMessagedActivity “User sent a message.” when UserLoggedOutActivity “User logged out.” else “Why isn’t this working” end => “Why isn’t this working”
5. case @activity when UserLoggedInActivity “User has logged in.” when UserMessagedActivity “User sent a message.” when UserLoggedOutActivity “User logged out.” else “Why isn’t this working” end => “User has logged in”
6. case @activity.class when UserLoggedInActivity “User has logged in.” when UserMessagedActivity “User sent a message.” when UserLoggedOutActivity “User logged out.” else “Why isn’t this working” end => “Why isn’t this working”
7. case @activity.class when UserLoggedInActivity “User has logged in.” when UserMessagedActivity “User sent a message.” when UserLoggedOutActivity “User logged out.” else “Why isn’t this working” end => “Why isn’t this working” => UserLoggedInActivity
8. case @activity.class when UserLoggedInActivity “User has logged in.” when UserMessagedActivity “User sent a message.” when UserLoggedOutActivity “User logged out.” else “Why isn’t this working” end => “Why isn’t this working” => UserLoggedInActivity UserLoggedInActivity == UserLoggedInActivity => true
9. UserLoggedInActivity == UserLoggedInActivity UserLoggedInActivity === UserLoggedInActivity
10. ===
11. === ‘Case equality operator’ ‘Triple equal operator’
13. What does the ‘===‘ do in Ruby?
14. What does the ‘===‘ do in Ruby?
15. What does the ‘===‘ do in Ruby?
16. What does the ‘===‘ do in Ruby?
17. What does the ‘===‘ do in Ruby?
19. Every object in Ruby inherits this method 1 === 1 1 == 1 => true => true “a” === “a” “a” == “a” => true => true @dog === @dog @dog == @dog => true => true
20. @activity.class === UserLoggedInActivity => false
21. @activity.class === UserLoggedInActivity => false @dog === Dog => false
22. String === “a” => true Array === [] => true Dog === @dog => true
23. String === “a” => true Array === [] => true Dog === @dog => true “Is this argument an instance of yourself?” “a”.is_a?(String) => true [].is_a?(Array) => true @dog.is_a?(Dog) => true
24. (1...10) === 5 => true Is 5 included in the range 1 through 10?
25. case @activity when UserLoggedInActivity “User has logged in.” when UserMessagedActivity “User sent a message.” when UserLoggedOutActivity “User logged out.” else “Why isn’t this working” end => “User has logged in” UserLoggedInActivity === @activity
27. String === “Thank you!” jcohenho.github.io