Ruby on Rails - How to arrange elements of array in particular order

Question

My array is:

[{:age=>28, :name=>"John", :id=>1}, {:name=>"David", :age=>20, :id=>2}]

Order:

[:id, :name, :age] or ['id', 'name', 'age']

The result should be:

[{:id=>1, :name=>"John", :age=>28}, {:id=>2, :name=>"David", :age=>20}]

P/s: I am using Ruby 1.8.7 and Rails 2.3.5

Thanks

If you want ordered hashes you'll need to upgrade to Ruby 1.9+. — Chris Heald, Feb 09 '15 at 17:43

score 2 · Answer 1 · answered Feb 09 '15 at 16:55

2

Order doesn't matter when it comes to hashes. You do not need to do that. Trust me.

What you're using is an Hash which, unlike Array doesn't care for positions. You only access the value by it's Symbol or Key.

So, there is no need of doing what you want to.

answered Feb 09 '15 at 16:55

Amit Joki

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OP clearly requested to sort an array and you are talking about hashes. – Aleksei Matiushkin Feb 09 '15 at 17:22
3

OP is obviously talking about hashes too, if you read the question. – Chris Heald Feb 09 '15 at 17:41
@ChrisHeald Yes, I misread a question as “sort an array by hash values.” My apologies. – Aleksei Matiushkin Feb 09 '15 at 18:12
1

I beg to differ. I have made good use of Ruby's maintenance of key insertion order in v. 1.9+. – Cary Swoveland Feb 09 '15 at 18:41

Cary Swoveland · Accepted Answer · 2015-02-09T21:32:55.583

As others have said, you cannot do that with Ruby 1.87 or prior. Here is one way to do that with Ruby 1.9+:

arr = [{:age=>28, :name=>"John", :id=>1}, {:name=>"David", :age=>20, :id=>2}]
order = [:id, :name, :age]

arr.map { |h| Hash[order.zip(h.values_at(*order))] }
  #=> [{:id=>1, :name=>"John", :age=>28}, {:id=>2, :name=>"David", :age=>20}]

In Ruby 2.0+, you can write:

arr.map { |h| order.zip(h.values_at(*order)).to_h }

I thought 1.8.7 went out with the steam engine.

Ruby on Rails - How to arrange elements of array in particular order

2 Answers2