hash assignment when (key => value) are stored in an array? (ruby)

Question

I have hash (@post) of hashes where I want to keep the order of the hash's keys in the array (@post_csv_order) and also want to keep the relationship key => value in the array.

I don't know the final number of both @post hashes and key => value elements in the array.

I don't know how to assign the hash in a loop for all elements in the array. One by one @post_csv_order[0][0] => @post_csv_order[0][1] works nicely.

#  require 'rubygems'
require 'pp'

@post = {}

forum_id = 123           #only sample values.... to make this sample script work
post_title = "Test post"

@post_csv_order = [
  ["ForumID" , forum_id],
  ["Post title", post_title]  
]

if @post[forum_id] == nil
  @post[forum_id] = {
    @post_csv_order[0][0] => @post_csv_order[0][1],
    @post_csv_order[1][0] => @post_csv_order[1][1]
    #@post_csv_order.map {|element| element[0] => element[1]}
    #@post_csv_order.each_index {|index|        @post_csv_order[index][0] => @post_csv_order[index][1] }
  }
end

pp @post

desired hash assignment should be like that

{123=>{"Post title"=>"Test post", "ForumID"=>123}}

---

Answers summary

working code #1

@post[forum_id] = @post_csv_order.inject({}) {|h,e| h[e[0]] = e[1]; h}

working code #2

@post[forum_id] = Hash[*@post_csv_order.flatten]

working code #3

@post[forum_id] ||= Hash[ @post_csv_order ] #requires 'require "backports"'

Answer 1

I am not sure I fully understand your question but I guess you want to convert a 2d array in a hash.

So suppose you have an array such as:

array = [[:foo,1],[:bar,2],[:baz,3]]

You can build an hash with:

hash = array.inject({}) {|h,e| h[e[0]] = e[1]; h}
# => {:foo=>1, :bar=>2, :baz=>3}

And you can retrieve the keys in correct order with:

keys = array.inject([]) {|a,e| a << e[0] }
=> [:foo, :bar, :baz]

Is it what you were looking for ?

Answer 2

Although it wasn't documented for a while, there is a very nice and simple answer to your question:

array = [[:foo,1],[:bar,2],[:baz,3]]
# then
Hash[ array ]  #= > {:foo => 1, :bar => 2, :baz => 3}

This is available in Ruby 1.8.7 and later, but if you are using Ruby 1.8.6 you can require "backports" and you are good to go.

In your case:

@post_csv_order = [
  ["ForumID" , forum_id],
  ["Post title", post_title]  
]
@post[forum_id] ||= Hash[ @post_csv_order ]