Finding blank arrays within ruby arrays Rails 4

Question

I am trying build a sentence out of 3 arrays with the count of each array.

cats = Cat.all 
dogs = Dog.all
birds = Bird.all 

animals = ["#{cats.count} Cats", "#{dogs.count} Dogs", "#{birds.count} Birds"]

sentence = animals.each.map{ |r| r  }.join(",  ")

Right now, this works, but if I have no cats sentence outputs to

"O Cats, 5 Dogs, 4 Birds"

and I'ld like it to just say:

"5 Dogs & 4 Birds"

or, at the very least:

"5 Dogs, 4 Birds"

I feel like I might need to use an array of hashes, but I'm a bit lost.

something simpler is to declare your animals array empty like animals = [], and then add elements one by one like: animals << "#{cats.count} Cats" if cats.count > 0. It all depends on how your implementation is done, so, this might work or not for you. — fanta
– fanta, Commented Oct 5, 2016 at 21:42

Aetherus · Accepted Answer · 2016-10-05 22:02:11Z

3

Yes, you need a hash.

cats = Cat.all 
dogs = Dog.all
birds = Bird.all

animals = {
  cats: cats.count,
  dogs: dogs.count,
  birds: birds.count
}

sentence = animals.reject{|k, v| v.zero?}
                  .map{|k, v| "#{v} #{k.to_s.capitalize}"}
                  .join(', ')

My suggestion: keep data as data till the last moment, so that you can have maximum flexibility to display it in various ways. I feel that the animals in your code thinks rendering too soon.

edited Oct 5, 2016 at 22:02

answered Oct 5, 2016 at 21:44

Aetherus

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4 Comments

user229044 Over a year ago

FYI: [Cat, Bird, Dog].map { |c| [c.class.name.pluralize, c.count].select { |a,b| b > 0 }.map(&:join).join(","). This is overly clever but parts of it are definitely worth employing to shorten the creation of the hash.

Sagar Pandya Over a year ago

perhaps use zero? here.

Aetherus Over a year ago

@sagarpandya82 Oh I didn't know that there's the method Numeric#zero?. It does make the code a bit cleaner. Thanks.

Aetherus Over a year ago

@meagar That's an interesting one liner. I didn't do this because I thought maybe the local variable cats and dogs and birds have other uses in OP's program.

davidhu · Accepted Answer · 2016-10-05 21:37:04Z

2

To get "5 Dogs, 4 Birds", you can do

sentence = animals.each.map{ |r| /^0\s/.match(r) ? nil : r  }.compact.join(", ")

The regex matches anything that starts with 0 and a space. If there is a match, return nil, or return the original string. The compact method removes nil elements from the array, and finally you join the elements.

If you want 5 Dogs & 4 Birds, you can define a method that performs that function.

def english_join(array)
  return array.to_s if array.nil? or array.length <= 1
  array[0..-2].join(", ") + " & " + array[-1]
end

Then you can do

sentence = english_join(animals.each.map{ |r| /^0\s/.match(r) ? nil : r  }.compact)

If you have 0 cats, 5 dogs, and 4 birds, this returns 5 Dogs & 4 Birds.

If you have 2 cats, 5 dogs, and 4 birds, this returns 2 Cats, 5 Dogs & 4 Birds

answered Oct 5, 2016 at 21:37

davidhu

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1 Comment

NothingToSeeHere Over a year ago

I'm torn between these two answers. As you are both right. Plus your english join is right on.

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