merging JSON Array with object - Rails 4- Ruby

Question

I am using Rails 4 and got following JSON output from different sources

source1

@something1 =   book.find().to_json

output

"[{\"a\": \"val1\"}]"

source2

@something2 =   Author.where(title: :autitle).pluck(:val2).to_json

Output

"[{\"b\": \"val2\"}]"

source 3

@something3 = Publications.find_by_pub_id(id)

Output

{ 
  "c":"val3",
  "d":" val4"
}

I want the final output like

{
  "a": "val1",
  "b": "val2",
  "c":"val3",
  "d":" val4"
}

I have used merge like

@newval= @something1[0].merge(@something2[0]).merge(@something3)

But, it gives error

undefined method merge!

Those variables are inside index method like

class Test controller < api::controller
  def index
   @something1 = ..
   @something2 = ..
   @something3 = ..
  end
end

Hope it is clear.

Can you include the complete log/error message? With the provided examples Ursus answer works fine (you can see it in action here), so maybe you are getting different outputs in the @something variables. — Gerry
– Gerry, Commented Aug 8, 2017 at 13:13
@Gerry while that example is nice (and functional) maybe we should be clear that the output in the question is inaccurate. JSON is a String and thus the correct output for the first example is actually "[{\"a\":\"val1\"}]". String does not have a merge method which would have been more obvious had the OP posted the full message. e.g. undefined method merge! for "[{\"a\":\"val1\"}]":String editted question for correct output — engineersmnky
– engineersmnky, Commented Aug 8, 2017 at 14:44
@Khoga remove the to_json calls from the first 2 and add it to the end of the merge chain. See Updated version of @Gerry's repl — engineersmnky
– engineersmnky, Commented Aug 8, 2017 at 14:54
@engineersmnky You are right, i completely missed (ignored?) the to_json, so now it makes sense. Thank you for claryfing it. — Gerry
– Gerry, Commented Aug 8, 2017 at 15:08
@engineersmnky Maybe you should add an answer, yours is the correct solution. — Gerry
– Gerry, Commented Aug 8, 2017 at 15:15

Ursus · Accepted Answer · 2017-08-08 11:44:53Z

2

With no more information this seems enough

@something1[0].merge(@something2[0]).merge(@something3)
{
    :a => "val1",
    :b => "val2",
    :c => "val3",
    :d => " val4"
}

answered Aug 8, 2017 at 11:44

Ursus

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1 Comment

Khoga Over a year ago

I have updated my question. Please let me know if you need more info.

engineersmnky · Accepted Answer · 2017-08-08 15:32:41Z

Your problem here is that JSON is a String thus

@something1 =   book.find().to_json
#=> "[{\"a\": \"val1\"}]"

This will make it far more difficult to deal with when trying to "merge" them together.

The error you are receiving is because String does not have a merge method (Next time please post the full error or at least the object reference) e.g. undefined method merge! for "[{\"a\":\"val1\"}]":String

Luckily the fix is extremely simple just remove to_json from the original 2 calls as such

require 'json'

@something1 = [{"a": "val1"}] # no to_json
@something2 = [{"b": "val2"}] # no to_json
@something3 = { "c": "val3", "d": " val4" } # no to_json

@something1[0].merge(@something2[0]).merge(@something3).to_json
#=> "{\"a\":\"val1\",\"b\":\"val2\",\"c\":\"val3\",\"d\":\" val4\"}"

See Example (based on @Gerry's original commented example)

Since this appears rails like we can probably simplify this whole process if we understood the relation ship between Book, Author and Publication eg.

Book.find().to_json(include: [:author,:publications]) 
# Or 
Book.find().to_json(include: [{author: {only: :name}},:publications])

This will avoid the need to merge as I fear the original example might actually need to be

@something1 =   book.find()
@something2 =   book.author
@something3 =   book.publications

@something1.attributes.merge({author: @something2.attributes,
    publications: @something3.map(&:attributes)}).to_json

m3characters · Accepted Answer · 2017-08-08 12:15:00Z

1

You can create a function like:

def mergejson(*args)
  merged = {}
  args.each do |a|
    merged.merge!(a.is_a?(Hash) ? a : a.first)
    # or use .deep_merge! if the hashes can contain nested hashes
  end
  return merged
end

irb(main):025:0> test = mergejson(something1, something2, something3)
=> {:a=>"val1", :b=>"val2", :c=>"val3", :d=>"val4"}

answered Aug 8, 2017 at 12:15

m3characters

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Comments

Evan · Accepted Answer · 2017-08-08 12:17:13Z

0

Also worked by:

@something1.first.merge(@something2.first).merge(@something3)

#=>{:a => "val1",:b => "val2",:c => "val3",:d => " val4"}

answered Aug 8, 2017 at 12:17

Evan

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1 Comment

Gerry Over a year ago

This is pretty much the same answer as the one provided by Ursus.

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