Ruby - Filtering array of hashes based on another array

Question

I am trying to filter an array of hashes based on another array. What's the best way to accomplish this? Here are the 2 brutes I've right now:

x=[1,2,3]
y = [{dis:4,as:"hi"},{dis:2,as:"li"}]

1) aa = []
x.each do |a|
  qq = y.select{|k,v| k[:dis]==a}
  aa+=qq unless qq.empty?
end

2) q = []
y.each do |k,v|
  x.each do |ele|
    if k[:dis]==ele
      q << {dis: ele,as: k[:as]}
    end
  end
end

Here's the output I'm intending:

[{dis:2,as:"li"}]

What's your desired output?

Mark Thomas
– Mark Thomas

2017-07-07 15:25:56 +00:00
Commented Jul 7, 2017 at 15:25 — Mark Thomas
– Mark Thomas, Commented Jul 7, 2017 at 15:25
@MarkThomas updated

linuxNoob
– linuxNoob

2017-07-07 15:28:56 +00:00
Commented Jul 7, 2017 at 15:28 — linuxNoob
– linuxNoob, Commented Jul 7, 2017 at 15:28

Mark Thomas · Accepted Answer · 2017-07-07 15:45:03Z

7

If you want to select only the elements where the value of :dis is included in x:

y.select{|h| x.include? h[:dis]}

edited Jul 7, 2017 at 15:45

answered Jul 7, 2017 at 15:29

Mark Thomas

37.6k11 gold badges78 silver badges101 bronze badges

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

5 Comments

linuxNoob Over a year ago

Simple and concise, thanks! I didn't know about include?

linuxNoob Over a year ago

Just one more question - Is it a bad idea to use select!, would storing it off and re-using be preferable? I don't need y anywhere else.

Cary Swoveland Over a year ago

The only possible improvement I can think of is to substitute the word "included" for "contained", so it reads "...select...included...".

Mark Thomas Over a year ago

Haha @CarySwoveland I thought the same thing, just didn't get around to updating it. Nice to meet a fellow pedant! (Now if we can just get the Ruby maintainers to make those methods plural...)

Mark Thomas Over a year ago

@linuxNoob Using select! is fine if you want to change it in place (or use keep_if which usually reads better to me).

dawg · Accepted Answer · 2017-07-07 17:29:43Z

1

You can delete the nonconforming elements of y in place with with .keep_if

> y.keep_if { |h| x.include? h[:dis] }

Or reverse the logic with .delete_if:

> y.delete_if { |h| !x.include? h[:dis] }

All produce:

> y
=> [{:dis=>2, :as=>"li"}]

edited Jul 7, 2017 at 17:29

answered Jul 7, 2017 at 17:06

dawg

105k24 gold badges142 silver badges217 bronze badges

Comments

Sagar Pandya · Accepted Answer · 2017-07-07 15:40:05Z

0

Yes use select, nonetheless here's another way which works:

y.each_with_object([]) { |hash,obj| obj << hash if x.include? hash[:dis] }

answered Jul 7, 2017 at 15:40

Sagar Pandya

9,5282 gold badges28 silver badges38 bronze badges

Collectives™ on Stack Overflow

Ruby - Filtering array of hashes based on another array

3 Answers 3

5 Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

5 Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related