Ruby 010

1. `"` vs `'`

Use double quotes if you want to do:

String interpolation.
Using escape sequences.

2. Back-tick (`)

A special use of back-ticks is with the puts method.

puts `ls`

will send the string ls as a command to the operating system, which in this case I believe you certainly know what the command does (unless you’re from Windows).

3. `String.eql?` vs `String.equal?`

String.eql? acts like the double equals operator (==), checks if two strings are identical.

String.equal? checks whether two strings are the same object.

a = "hello"
b = "hello"
c = b

puts a.eql? b # prints "true"
puts a.equal? b # prints "false"
puts b.equal? c # prints "true"

4. `&&` vs `and`, `||` vs `or`, `!` vs `not`

They are not the same. They differ in precedence. The character operators (&&, ||, and !) have higher precedence than the word operators (and, or, and not).

5. Code blocks

Duck: “Hey, JavaScript developers! Take a look at this.”

foo() {
  puts "Hi there!"
}

JS devs: “What is this? Is this a function declaration?”

Duck: “Nah… Don’t be fooled! It’s a function (or more correctly, method) invocation. The braces are a code block that’s passed to the method foo. Think of it as a callback function in JavaScript. The foo method can execute the code block whenever it wants by using the keyword yield.”

def foo
  puts "I am a function, foo!"
  yield
end

foo() {
  puts "Hi there!"
}

# Output is:
# I am a function, foo!
# Hi there!

Code blocks also have another syntax: do ... end.

foo() do
  puts "Hi there!"
end

6. Multiple return values

def calc(n)
  return 1 * n, 2 * n, 3 * n
end

a, b, c = calc(5)
puts "#{a}, #{b}, #{c}" # prints "5, 10, 15"

Ruby can return multiple values from a method, much like Go. However, it’s not a native feature.

You have to explicitly use the return keyword for it to work. Under the hood, Ruby actually wraps the return values in an array and return it. On the left side of the assignment, we use a syntax called parallel assignment that extracts the corresponding values from the returned array and assign them to each variable.

7. Checking if a value falls within a range

def is_two_digit_number?(n)
  (10...99) === n
end

puts is_two_digit_number?(3) # prints "false"
puts is_two_digit_number?(33) # prints "true"

Ranges in Ruby can be created using the .. and ... operators.

.. creates an inclusive range. In math: [low, high]
... creates an exclusive range. In math: [low, high)

The triple equals operator (===) is used to check whether a value is within a range.

1. " vs '