Transmute hash structure [closed] - ruby

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I have a large JSON object as such (but x100+):
[
{
"category": "category1",
"text": "some text"
},
{
"category": "category2",
"text": "some more text"
},
{
"category": "category1",
"text": "even more text"
}
]
How would I transmute this into:
{
"category1": [
{
"text": "some text"
},
{
"text": "even more text"
}
],
"category2": {
"text": "even more text"
}
}
Any help in the right direction would be appreciated.

Answer 1

First you need to convert your JSON string into Ruby Object.
require "json"
json = %{
[
{
"category": "category1",
"text": "some text"
},
{
"category": "category2",
"text": "some more text"
},
{
"category": "category1",
"text": "even more text"
}
]
}
ary = JSON.parse(json)
Now that we have an array of hashes in Ruby form, we can manipulate it
h = ary.group_by {|i| i["category"]}
#=> {"category1"=>[{"category"=>"category1", "text"=>"some text"}, {"category"=>"category1", "text"=>"even more text"}], "category2"=>[{"category"=>"category2", "text"=>"some more text"}]}
h = h.map {|k,v| {k => v.map {|t| {"text" => t["text"]}}}}
#=> [{"category1"=>[{"text"=>"some text"}, {"text"=>"even more text"}]}, {"category2"=>[{"text"=>"some more text"}]}]
h = h.reduce(&:merge)
#=> {"category1"=>[{"text"=>"some text"}, {"text"=>"even more text"}], "category2"=>[{"text"=>"some more text"}]}
Print the JSON in pretty form to check the result
puts JSON.pretty_generate(h)
Output:
{
"category1": [
{
"text": "some text"
},
{
"text": "even more text"
}
],
"category2": [
{
"text": "some more text"
}
]
}

Answer 2

def transmute(arr)
out = Hash.new { |hash, key| hash[key] = [] }
arr.inject(out) do |h, e|
key = e[:category].to_sym
entry = {text: e[:text]}
h[key] << entry
h
end
end
Working code/spec snippet:
http://rubysandbox.com/#/snippet/56784c32793916000c000000

Answer 3

Assuming to get "category2": [{"text": "some more text"}] in the result:
array.map(&:dup).group_by{|h| h.delete(:category)}

Answer 4

Enumerable#each_with_object might help. Something like
json.each_with_object({}) do |h, acc|
acc[h[:category]] ||= []
acc[h[:category]] << {text: h[:text]}
end # {"category1"=>[{:text=>"some text"}, {:text=>"even more text"}], "category2"=>[{:text=>"some more text"}]}
where json is your original array.