Ruby Variable Binding Inside Loops

Question

I need to loop through an aliases hash, and transform the header array by assigning it values from the aliases hash in a Ruby class.

I can't seem to transform the header array and then have it available after the loop.

How do I transform the header array so it is available for use after the loop?

 header = ["City", "State"]

 aliases = {"City"=>"Las Vegas", "State"=>"Nevada"}

 aliases.each do |k,v|
   header.each do |s|   
     if s == k then
       s = v            
     end
   end
 end

 puts header

This code runs fine. "sees" everything it should see (but you assert that it doesn't). — Sergio Tulentsev
– Sergio Tulentsev, Commented Feb 1, 2018 at 15:52
You're correct, I think the issue may be that s=v does not change the header. — GavinBelson
– GavinBelson, Commented Feb 1, 2018 at 16:07
In future, don't be in such a rush to select an answer! Quick selections may discourage other answers, and by waiting awhile (at least a couple of hours, say) readers may point out weaknesses in answers that you may not have thought of. Note that you can always change your selection. Incidentally, I see no reason for the Rails tag. — Cary Swoveland
– Cary Swoveland, Commented Feb 1, 2018 at 20:35

Ronan Lopes · Accepted Answer · 2018-02-01 18:01:09Z

2

Try it like this:

header = ["City", "State"]

 aliases = {"City"=>"Las Vegas", "State"=>"Nevada"}

 aliases.each do |k,v|
   header.each do |s|   #doesn't see header variable
     if s == k 
      header[header.index(s)] = v            #doesn't see v variable
     end
   end
 end

 puts header

Don't know if I got it right, think it's what you're looking for. Good luck!

EDIT: I would still simplify it like this:

header = ["City", "State"]

aliases = {"City"=>"Las Vegas", "State"=>"Nevada"}

header.each do |s|
  aliases.select{|k,v| k==s}.each do |k,v|
    header[header.index(s)] = v
  end
end
puts header

edited Feb 1, 2018 at 18:01

answered Feb 1, 2018 at 15:54

Ronan Lopes

3,4004 gold badges31 silver badges52 bronze badges

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

14 Comments

GavinBelson Over a year ago

Thanks, that works. It looks like header was getting looped over but the values did not change with my code. Indexing it solves the issue

Sergio Tulentsev Over a year ago

you call that a simplification? :) header.map! {|s| aliases[s] }

Sergio Tulentsev Over a year ago

header = aliases.values_at(*header)

Sergio Tulentsev Over a year ago

OP would do well to learn to avoid mutating stuff like this. Suddenly header is not a header (does not contain header-y values). Makes code impossible to read.

Sergio Tulentsev Over a year ago

@RonanLopes: I wasn't. That snippet is objectively more complex than the one before. If you don't mind, what exactly is simpler about it? :)

|

Collectives™ on Stack Overflow

Ruby Variable Binding Inside Loops

1 Answer 1

14 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

14 Comments

Your Answer

Sign up or log in

Post as a guest

Related