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.
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"}
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"}]
