Ruby gotchas Part 1

Feel free to skip this if you eat gems 💎 for breakfast or you take rails 🛤️ everyday.

🥁🥁 (Ba dum tss)

Here's some tidbits of information and "gotchas" that I had learning Ruby, as someone coming from JS-land.

NOTE: I'm using irb with Ruby 2.6.5

1.✨ Ruby is dynamically-typed like JS

Dynamic means the type of the variable is resolved on-the-fly and can be changed at run time (hence, dynamic).

compared to static typed like Java or TypeScript

No need for types when declaring variable, and the value assigned to variable can be of any type.

me = 3  # int
me = "I'm dynamic"  # string
me = {:a=>"fancy", :b=>"object"}  # object

2.🔢 Integer() vs to_i

Integer() errors out with non-Integer strings

while to_i tries really hard, and spits out 0 if it can't

"a1".to_i
=> 0

Integer("a1")
=> ArgumentError (invalid value for Integer(): "a1")

Same with Float(str) and str.to_f as well

floaty = "3.14"
puts floaty.to_f + 0.01
=> 3.15

Converting from other bases

The nice thing with Integer(str, radix) is that you can also use it to convert other bases to integer, just like parseInt() in JS.

E.g. if you want to convert binary to integer

Integer("101", 2)
=> 5

3.📦 Everything is an object

Just like in Python, but not exactly like Javascript (un-boxed primitives like strings, numbers are not objects).

You can use "me".methods to see all supported methods of String "me" and Integer 123

"me".methods
=> ["upcase!", "empty?, "to_f", "to_i", "length",...]

123.methods
=> ["to_s", "odd?", ".even?", ...]

4.🦆 Duck-typing and respond_to?

Duck-typed means an object is considered a "Duck" if it has methods of a duck: it walks like a duck, it quacks like a duck.

For example, if 123 has odd? and even? methods, then it must be an Integer?! Use respond_to? to check whether an object is able to do / has something, instead of using .methods everytime

123.respond_to?("odd?")
=> true

5.🎚️ Ranges (1..5) and using them in loops

A Range is a sequence of values that can be used as a collection or converted easily to an array using to_a

Use .. for including high value and ... for excluding it

Use as a collection for iterating

1..2
=> #<Enumerator: 1..2:each>

(1..3).each {|n| puts n}

1
2
3
=> 1..3

(1...3).each {|n| print n}
12=> 1...3

🔖 print doesn't include a newline like puts does

⚠️ Don't use for loops!

You can also use ranges in loops, but note that it is not common and iterators should be used most of the time.

For loops are also considered bad in the Rubocop style guide, since the variables defined inside it leaks outside of the loop

❌
for i in (1..5)
    print i
end
=> 12345

puts i
=> 5 
😱

✔️
(1..5).each {|i| print i}
12345=> 1..5

puts i
=> NameError (undefined local variable or method `i')
😎

For more info: https://rubystyle.guide/#no-for-loops

Use as an array

(1..5).to_a
=> [1, 2, 3, 4, 5]

(1...5).to_a
=> [1, 2, 3, 4]

Works in characters too!

('1x'..'2b').to_a
=> ["1x", "1y", "1z", "2a", "2b"]

And you can check if an item is inside a range

('a'...'e').include? 'b'
=> true
('a'...'e').include? 'z'
=> false

---

That's all for now. 😄

I'm not a Ruby ninja 🤺 (yet),
and these are mostly observations for me.
So let me know of any corrections and improvements in the comments. 👇

Happy Ruby-ing! 💎

Comments

[Daniel Kassen]

I've actually never used a for loop in ruby. It is most conventional to loop over an enumerable using something like .each

[Lenmor Ld]

Thanks for the note! 🙏🏻
It's actually even discouraged in Rubocop style guide. 😳
I'll update the post :)