CODEWITHSUNDEEP
arraysjsonrubyhash
adbarads
adbarads

Reputation: 1303

ruby how to add a hash element into an existing json array

I have code that outputs the following:

car_id = ["123"]
model = [:model].product(car_id).map { |k,v| {k=>v} }
model = [{:model=>"123"}]

I would like to then add a new hash :make into the json like this:

model_with_make = [{:model=>"123", :make => "acura"}]

How do I do this?

Unfortunately, every solution I find produces this: [{:model=>"123"}, {:make => "acura"}] and that is not what I want.

Upvotes: 0

Views: 240

Answers (2)

Cary Swoveland
Cary Swoveland

Reputation: 110675

Ruby convention for showing result of a calculation

I assume you mean that

model = [:model].product(car_id).map { |k,v| {k=>v} }

produces an array containing a single hash:

[{:model=>"123"}]

and that you are not then executing the statement:

model = [{:model=>"123"}]

which would overwrite the the value of model from the previous statement, rendering the previous statement meaningless. If so, the normal way to write that is as follows.

model = [:model].product(car_id).map { |k,v| {k=>v} }
  #=> [{:model=>"123"}]

Computing the array

Next,

arr = [:model].product(car_id)
  #=> [[:model, "123"]]

But why use Array#product when the arrays [:model] and car_id both contain a single element? It's simpler to just write

arr = [[:model, car_id.first]]
  #=> [[:model, "123"]]

Converting the array to a hash

Since arr contains only one element, there's not much point to mapping it; just convert it to a hash:

Hash[arr]
  #=> {:model=>"123"}

or (for Ruby versions 1.9+):

arr.to_h
  #=> {:model=>"123"}

Add a key-value pair to the hash

If you wish to add the key-value pair :make => "acura" to

h = {:model=>"123"}

you can simply write

h[:make] = "acura"
  #=> "acura" 
h #=> {:model=>"123", :make=>"acura"}

or, in one line,

(h[:make] = "acura") && h
  #=> {:model=>"123", :make=>"acura"}

Wrapping up

Putting this together, you could write

h = [[:model, car_id.first]].to_h
  #=> {:model=>"123"} 
(h[:make] = "acura") && h
  #=> {:model=>"123", :make=>"acura"}

Upvotes: 2

Aleksei Matiushkin
Aleksei Matiushkin

Reputation: 121000

model = [{:model=>"123"}]
model_with_make = model.map { |m| m.merge(make: 'acura') }
#⇒ [{:model=>"123", :make => "acura"}]

If you are concerned that there is the only element in the array model, you might modify it inplace:

model.first.merge!(make: 'acura')
model
#⇒ [{:model=>"123", :make => "acura"}]

Upvotes: 1

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