Question

The actual problem I was originally doing was converting a hash of arrays into an array of hashes. If anyone has any comments on doing the conversion then that’s fine but the actual question I have is why the order of the hash keys change after editing them.

I’m fully aware of this question but this is not a duplicate. In fact I’m just having specific toruble in the order they are coming out in.

I have one array and one hash.

The array (@headers) contains a list of keys. @contents is a Hash filled with arrays. As explained, my task is to get an Array of hashes. So here’s my code, pretty straightforward.

@headers = (params[:headers])
puts "ORIGINAL PARAMS"
puts YAML::dump(@headers)


 @contentsArray = []  #The purpose of this is to contain hashes of each object

    @contents.each_with_index do |page,contentIndex|
      @currentPage = Hash.new

      @headers.each_with_index do |key, headerIndex|
        @currentPage[key] ="testing"
      end
      puts YAML::dump(@currentPage)
      @contentsArray[contentIndex] =@currentPage
    end
    puts "UPDATED CONTENTS"
    puts YAML::dump(@contentsArray[0])

Heres the bit I cant wrap my head around. The keys of the original params are in a different order than the updated one.

Note the :puts “ORIGINAL PARAMS” & puts “UPDATED CONTENTS” parts. This is their output:

ORIGINAL PARAMS
--- 
- " Page Title      "
- " WWW "
- " Description     "
- " Keywords        "
- " Internal Links  "
- " External Links  "
- " Content files   "
- " Notes           "
--- 


UPDATED CONTENTS
--- 
" WWW ": page
" Internal Links  ": testing
" External Links  ": testing
" Description     ": testing
" Notes           ": testing
" Content files   ": testing
" Page Title      ": testing
" Keywords        ": testing

Why is this?

for the record. Printing @currentPage after the header loop gives this:

" WWW ": page
" Internal Links  ": page
" External Links  ": page
" Description     ": page
" Notes           ": page
" Content files   ": page
" Page Title      ": page
" Keywords        ": page

So it must be the way the values and keys are assigned to the @currentPage and not when It goes into the array.

Answer 1

In Ruby 1.8+ Hashes are UNSORTED lists

The order in which you traverse a hash by either key or value may seem arbitrary, and will generally not be in the insertion order.

While in RUBY 1.9+ they are sorted in order you push items.

Hashes enumerate their values in the order that the corresponding keys were inserted.

http://apidock.com/ruby/v1_9_2_180/Hash