How can I iterate over an array of hashes and form new one

Question

I have a call to Companies House API and response I get from API is an array of hashes.

companies = { "total_results" => 2, "items" => [{ "title" => "First company", "date_of_creation" => "2016-11-09", "company_type" => "ltd", "company_number" => "10471071323", "company_status" => "active" }, { "title" => "Second company", "date_of_creation" => "2016-11-09", "company_type" => "ltd", "company_number" => "1047107132", "company_status" => "active" }] }

How I can iterate over companies and get a result similar to:

[{ title: "First company", company_number: "10471071323" }, { title: "Second company", company_number: "1047107132" }]

Does this answer your question? What is the "right" way to iterate through an array in Ruby? — cesartalves
– cesartalves, Commented Jun 12, 2020 at 12:44

Fernando Briano · Accepted Answer · 2020-06-12 12:47:46Z

You can use map which will iterate through the elements in an array and return a new array:

companies["items"].map do |c| { title: c['title'], company_number: c['company_number'] } end => [ {:title=>"First company", :company_number=>"10471071323"}, {:title=>"Second company", :company_number=>"1047107132"} ]

Thanks @Fernando, this worked out for me. I have as well added #dig method to avoid NoMethodError: undefined method '[]' for nil:NilClass

Clemens Kofler · Accepted Answer · 2020-06-14 10:01:07Z

0

companies.map { |company| company.slice('title', 'company_number').symbolize_keys }

This should do the trick.

If you're not using Rails (or, more specifically, ActiveSupport), then symbolize_keys won't be available. In this case, you'd have to go for a more standard-Ruby approach:

companies.map do |company| { title: company["title"], company_number: company["company_number"] } end

edited Jun 14, 2020 at 10:01

answered Jun 12, 2020 at 12:47

Clemens Kofler

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3 Comments

Sebastián Palma Over a year ago

slice keeps the string keys.

Clemens Kofler Over a year ago

Fair enough. If Rails is being used, you can add symbolize_keys: companies.map { |company| company.slice('title', 'company_number').symbolize_keys }

Jeremy Caney Over a year ago

@ClemensKofler: It may be useful to update your original answer to include that alternate option, and a better explanation of when one is useful compared to the others.

Tom Harvey · Accepted Answer · 2020-06-15 17:10:12Z

The answers are totally correct; but you should be made aware that what you’re looking at from companies house is not just an array of hashes - it’s a valid JsonApi response.

You might find your job easier if you’re using a gem which is aware of JsonApi specs, or if you’re just approaching it as that kind of data.

Have a look at the ruby implementations of https://jsonapi.org/implementations/

Or ActiveModelSerializer for ways to not only reform your hashes but deserialise this very structured data into ruby objects.

But like I say, if all you’re looking for is a quick way to reform the data as you describe. The above answers are perfect.

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