Nested json from ruby hash

Question

Trying to build a json out of Ruby hash

require 'json'
temp_rides = {"rides": {}}
rides = {:lyft => "car", :scoot => "scooter", :blade => "helicopter"}
rides.each do |key, value|
 temp_rides["rides"].push({"key" => "value"})
 puts temp_rides
end

apparently it fails with undefined methodpush'` I believe I need to load the json object before append (based on my python background).

I am looking for a output something like this

{
    "rides": {
        "lyft": {
            "type": "car"
        },
        "scoot": {
            "type": "scooter"
        },
        "blade": {
            "type": "helicopter"
        }
    }
}

That's going to require some work as your keys are labelled rideN, but not very consistently. type vs. type2 for instance. — tadman
– tadman, Commented Oct 18, 2019 at 1:07
@tadman thanks for the input, true not consistent. I just fixed it. — Chucks
– Chucks, Commented Oct 18, 2019 at 1:56
You changed the question! You can't do that. Among other things it renders answers nonsensical. — Cary Swoveland
– Cary Swoveland, Commented Oct 18, 2019 at 2:22

Cary Swoveland · Accepted Answer · 2019-10-18 03:05:22Z

This is an answer to the OP's original question. I have no interest in changing it to attempt to answer a moving target.

Code

def doit(rides)
  { rides: rides.slice_before { |k,_| k.to_s.match? /\Aride\d*\z/ }.
                 map { |a| hashify(a.flatten.drop(1)) }.
                 reduce(&:merge) }
end

def hashify(arr)
  f,*rest = arr
  return f if rest.empty?
  { f.to_sym=>hashify(rest) }
end

Examples

Here is an example of the use of the (recursive) helper method hashify:

hashify ["lyft", :type, "car"]
  #=> {:lyft=>{:type=>"car"}}

We are given the hash rides:

rides = {:ride1=>"lyft", :type=>"car", :ride2=>"Scoot",
         :type2=>"scooter", :ride3=>"blade", :type3=>"helicopter"} 
doit rides
  #=> {:rides=>{:lyft=>{:type=>"car"},
  #             :Scoot=>{:type2=>"scooter"},
  #             :blade=>{:type3=>"helicopter"}}}

Let's add some more key-value pairs to rides:

rides = {:ride1=>"lyft", :type=>"car", :color=>"blue",
         :ride2=>"Scoot", :type2=>"scooter", :make=>"Vespa", :model=>"98",
         :ride3=>"blade", :type3=>"helicopter"} 
doit rides
  #=> {:rides=>{:lyft=>{:type=>{:car=>{:color=>"blue"}}},
  #             :Scoot=>{:type2=>{:scooter=>{:make=>
  #                       {:Vespa=>{:model=>"98"}}}}},
  #             :blade=>{:type3=>"helicopter"}}}

Explanation

The steps for the first example are as follows.

enum = rides.slice_before { |k,_| k.to_s.match? /\Aride\d*\z/ }
  #=> #<Enumerator: #<Enumerator::Generator:0x00005a49d68217f0>:each>

We can see the elements that will be generated by this enumerator by converting it to an array.

enum.to_a
  #=> [[[:ride1, "lyft"], [:type, "car"]],
  #    [[:ride2, "Scoot"], [:type2, "scooter"]],
  #    [[:ride3, "blade"], [:type3, "helicopter"]]]

Continuing,

a = enum.map { |a| hashify(a.flatten.drop(1)) }
  #=> [{:lyft=>{:type=>"car"}},
  #    {:Scoot=>{:type2=>"scooter"}},
  #    {:blade=>{:type3=>"helicopter"}}] 
h = a.reduce(&:merge)
  #=> {:lyft=>{:type=>"car"}, :Scoot=>{:type2=>"scooter"},
  #    :blade=>{:type3=>"helicopter"}} 
{ rides: h } 
  #=> <as above>

halfelf · Accepted Answer · 2019-10-18 02:09:06Z

1

It gave you undefined method push because there is no such method for a hash.

temp_rides = {"rides": {}} 
# This create a hash with `:rides` symbol as the key {:rides=>{}}

# To push an object into a hash. Use operator[]= or #store method
temp_rides[:rides][:key1] = 'value1'
temp_rides[:rides].store(:key2, 'value2')

A working example:

require 'json'

temp_rides = {"rides": {}}
rides = {:lyft => "car", :scoot => "scooter", :blade => "helicopter"}
rides.each_pair do |k, v|
    temp_rides[:rides][k] = {:type => v}
end

puts JSON.pretty_generate(temp_rides)

edited Oct 18, 2019 at 2:09

answered Oct 18, 2019 at 2:02

halfelf

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Comments

tadman · Accepted Answer · 2019-10-18 01:59:56Z

1

This is actually pretty easy to do with a simple transform:

def rejig(rides)
  rides.map do |name, type|
    [ name, { type: type } ]
  end.to_h
end

Where that will rework your structure into the desired shape.

Using it is easy:

require 'json'

rides = { lyft: "car", scoot: "scooter", blade: "helicopter" }

puts JSON.dump(rejig(rides))
# => {"lyft":{"type":"car"},"scoot":{"type":"scooter"},"blade":{"type":"helicopter"}}

answered Oct 18, 2019 at 1:59

tadman

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1 Comment

Nate Over a year ago

Any reason you’re creating so many needless arrays when the output is all hashes? You’ve got N+1 arrays and N hashes when you need N+2 hashes. That’s a lot of waste.

Ashok Damaniya · Accepted Answer · 2019-10-18 04:47:05Z

0

require 'json'
temp_rides = {"rides": {}}
rides = {:lyft => "car", :scoot => "scooter", :blade => "helicopter"}
temp_rides[:rides].merge!(rides)

to get ruby hash output

temp_rides

to get json format output

JSON.dump temp_rides

answered Oct 18, 2019 at 4:47

Ashok Damaniya

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Comments

Nate · Accepted Answer · 2019-10-18 05:37:43Z

0

require 'json'

rides = {:lyft => "car", :scoot => "scooter", :blade => "helicopter"}

transformed = {
  'rides' => rides.inject({}) { |h,(k,v)| h[k] = { 'type' => v }; h }
}

JSON.dump(transformed)

answered Oct 18, 2019 at 5:37

Nate

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