Converting an array with only one object in Ruby

Question

Say I have an array, and I use the keep_if or select methods to delete everything but one object for the array -- is there a way to take that object out of the array, so it's not an array any more?

For example, the way my models are set up, previous and current will only ever have one object.

 def more_or_less?(project, current_day)
    words = project.words
    current = words.select {|w| w.wrote_on == current_day}
    previous = words.select {|w| w.wrote_on == (current_day - 1.day)}
 end

So, if I want to do a comparison, like if current.quantity > previous.quantity -- I've resorted to actually writing if current.last.quantity > previous.last.quantity but I'm assuming there's a more idiomatic way?

mu is too short · Accepted Answer · 2011-09-09 04:20:28Z

2

If you're deleting all but one entries, why not use find to choose the one thing you care about? Something like this:

def more_or_less?(project, current_day)
  words    = project.words
  current  = words.find { |w| w.wrote_on == current_day }
  previous = words.find { |w| w.wrote_on == (current_day - 1.day) }
  if current.quantity > previous.quantity
    #...
  end
end

If you're in ActiveRecord land, then you can use detect as derp says or to_a to get a plain array that you can use find on:

def more_or_less?(project, current_day)
  words    = project.words
  current  = words.detect    { |w| w.wrote_on == current_day }
  previous = words.to_a.find { |w| w.wrote_on == (current_day - 1.day) }
  if current.quantity > previous.quantity
    #...
  end
end

edited Sep 9, 2011 at 4:20

answered Sep 9, 2011 at 3:43

mu is too short

436k71 gold badges863 silver badges822 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

Slick23 Over a year ago

No, that's what I was looking for. Why didn't occur to me that find would work, I don't know.

Slick23 Over a year ago

Actually -- I'm in a Rails project, so when I use find it's looking for a primary key.

mu is too short Over a year ago

What is words then? Is it a single ActiveRecord object?

Slick23 Over a year ago

words is an array (project has_many => :words), that's why I'm selecting out of it in the first place.

derp · Accepted Answer · 2011-09-09 04:01:39Z

1

detect is an alias for find, maybe that would work

answered Sep 9, 2011 at 4:01

derp

3,07020 silver badges16 bronze badges

Collectives™ on Stack Overflow

Converting an array with only one object in Ruby

2 Answers 2

4 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

4 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related