Class inheritance (from Array) and custom methods in Ruby

Question

I'm up against something I don't quite understand.

Here's the class I've created, and the driver code I'm running to test my method:

class Dog < Array
  def breathing?
    self.length > 1
  end
end

the_dog = Dog.new(["Arf", "Woof"])

puts the_dog.breathing?
# true

the_dog.shift

puts the_dog.breathing?
# false

How come, when I call #shift on the_dog, the_dog stops breathing?

Because the_dog.length isn't greater than 1. Did you want to use>=? Also, inheriting from core classes might not go well (sadly), use instance variables. — cremno
– cremno, Commented Jul 10, 2015 at 18:02
Especially inheriting from Array is bad. I have yet to see a use case where it'd be warranted. — Sergio Tulentsev
– Sergio Tulentsev, Commented Jul 10, 2015 at 18:06
I think it's disrespectful to name man's best friend, "the_dog". — Cary Swoveland
– Cary Swoveland, Commented Jul 11, 2015 at 4:36

MurifoX · Accepted Answer · 2015-07-10 19:58:47Z

1

Shift method returns the first element of self and removes it (shifting all other elements down by one). Returns nil if the array is empty.

a = [1,2,3]
a.shift
=> [2,3]

So, In your case the first argument of the array is removed. Once its removed, the condition the_dog.breathing? is returned false.

edited Jul 10, 2015 at 19:58

MurifoX

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answered Jul 10, 2015 at 18:22

Venkatesh Dhanasekaran

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