The document discusses common mistakes made by workshop applicants including string concatenation versus string interpolation, control flow issues like nested if/else statements that could be simplified with guard clauses, N+1 query problems that can be solved with eager loading, passing too many options to methods, exposing secrets in code repositories, duplicating styles, and using incorrect syntax for the template language being used. It provides examples of better approaches for each case discussed.

1. Most common mistakes of
workshops’ applicants
Robert Kuśmirek

2. String concatenation
def full_name_with_title
full_name + ” [“ + title + “]”
end

3. It works… But it’s not ruby!

4. def full_name_with_title
“#{full_name} [#{title}]”
end
Use string interpolation
In 99.9999% cases that’s what you need

5. if kitten.cute?
attempt_capture
else # highly unlikely
kitten.groom
kitten.apply_ribbon
kitten.pat_on_the_head
end
Control flow

6. I’d rather see you using Guard Clause
Again, this is a better choice in 99.99999% cases
return attempt_capture if kitten.cute?
kitten.groom
kitten.apply_ribbon
kitten.pat_on_the_head

7. During code review, what would you rather see…
~ or ~
Big Commits

8. Exactly.

9. N+1 Query
# models
class Cat < ActiveRecord::Base
belongs_to :crazy_cat_lady
end
class CrazyCatLady < ActiveRecord::Base
has_many :cats
end
# in controller
expose(:cats) { Cat.limit(5) }
# in view
cats.each do |cat|
= cat.crazy_cat_lady
end

10. This results in mayhem in your logs
Cat Load (0.9ms) SELECT 'cats'.* FROM 'cats'
CrazyCatLady Load (0.4ms) SELECT 'crazy_cat_ladies'.* FROM 'crazy_cat_ladies' WHERE
'crazy_cat_ladies'.'id' = ? ORDER BY 'crazy_cat_ladies'.'id' ASC LIMIT 1 [["id", 1]]
CrazyCatLady Load (0.3ms) SELECT 'crazy_cat_ladies'.* FROM 'crazy_cat_ladies' WHERE
'crazy_cat_ladies'.'id' = ? ORDER BY 'crazy_cat_ladies'.'id' ASC LIMIT 1 [["id", 2]]
CrazyCatLady Load (0.4ms) SELECT 'crazy_cat_ladies'.* FROM 'crazy_cat_ladies' WHERE
'crazy_cat_ladies'.'id' = ? ORDER BY 'crazy_cat_ladies'.'id' ASC LIMIT 1 [["id", 3]]
CrazyCatLady Load (0.3ms) SELECT 'crazy_cat_ladies'.* FROM 'crazy_cat_ladies' WHERE
'crazy_cat_ladies'.'id' = ? ORDER BY 'crazy_cat_ladies'.'id' ASC LIMIT 1 [["id", 4]]
CrazyCatLady Load (0.4ms) SELECT 'crazy_cat_ladies'.* FROM 'crazy_cat_ladies' WHERE
'crazy_cat_ladies'.'id' = ? ORDER BY 'crazy_cat_ladies'.'id' ASC LIMIT 1 [["id", 5]]

11. Eager loading for the rescue!
expose(:cats) { Cat.includes(:crazy_cat_ladies).limit(5)}

12. Cat Load (0.4ms) SELECT 'cats'•.* FROM 'cats'•
CrazyCatLady Load (0.4ms) SELECT 'crazy_cat_ladies'•.* FROM 'crazy_cat_ladies'•
WHERE 'crazy_cat_ladies'•.'•id'•IN (1,2,3,4,5)
Much better.

13. Bullet

14. def cuddle_with_kitten(options = {})
# cuddling-related code
end
cuddle_with_kitten({cat: ‘Pinky’, cuddle: :furiously})
So many options!

15. You can drop the {braces} when options are
the last argument!
How cool is that? And cleaner too.
cuddle_with_kitten(cat: ‘Pinky’, cuddle: :furiously)

16. Decorator Pattern

17. DON’T push API tokens and secrets to repos.
Everytime you do it a cute kitten dies.

18. Use secrets.yml.
Or figaro.
Or something.
Anything!

19. There are variables in scss.
Use them!
.kitten {
fur-color: #e2e2e2;
}
.horse {
fur-color: #e2e2e2; <= duplication spotted!
}

20. Duplication is #uncool.
$gray-fur-color: #e2e2e2;
.kitten {
fur-color: $gray-fur-color;
}
.horse {
fur-color: $gray-fur-color;
}

21. And last but not least...
# in view
= “#{t(‘something.clever’)}”

22. This is HAML, doug!
It tries very hard to be your best friend!
# in view
= t(‘something.clever’)}
~ or ~
#{t(‘something.even.cleverer’)} # Look, Ma! No ‘=’!