Pass variable from Controller to Serializer in Rails

Question

I have this code in my Controller to get distance in meters from one location to another location:

range = Geocoder::Calculations.distance_between([lat,lng],[Model.location.lat,Model.location.lng])
rangeInMeters = range * 1000            
rangeRounded = rangeInMeters.round
rangeRounded = rangeRounded / 100 * 100

and I have this code in my serializer to give a nicer output for the json response like this:

class ModelSerializer < ActiveModel::Serializer
  attributes :id, :name, :address, :range

  def range
  // something
  end
end

How to get rangeRounded be read by ModelSerializer so in json response it would be like this:

{
        "id": 1,
        "name": "Name A",
        "address": "Address A",
        "range": 500
    },

this answer should help: https://stackoverflow.com/a/37956952/2545197 — Abhinay, Jan 18 '18 at 11:48
sure, `attributes :id, :name, :address, :range # has_many :locations def range puts @instance_options[:rangeRounded] end` — rony, Jan 18 '18 at 11:56

Mikhail Katrin · Accepted Answer · 2018-01-18T12:33:27.957

3

If I understood correctly your model has location which has lat and lng. And you want to access these fields in your serializer method.

You can access these fields using object.

RailsCasts - Active Model Serializers episode

#controller
def action
    ...
    range = Geocoder::Calculations.distance_between([lat,lng],[Model.location.lat,Model.location.lng])
    range_in_meters = range * 1000            
    range_rounded = range_in_meters.round
    range_rounded = range_rounded / 100 * 100
    ...

    render json: @model, serializer: ModelSerializer, range_rounded: range_rounded
end


#serializer
class ModelSerializer < ActiveModel::Serializer
    attributes :id, :name, :address, :range
    #point assosiations here (same as in model)

    def range
        puts @instance_options[:range_rounded]
    end
end

edited Jan 18 '18 at 12:33

answered Jan 18 '18 at 11:58

Mikhail Katrin

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could you please elaborate? I'm still learning about this serializer. Thank you very much. – rony Jan 18 '18 at 12:14
Provide your controller code where you want to respond with serialized `model`, and model – Mikhail Katrin Jan 18 '18 at 12:21
the `rangeRounded` variable that needed to be serialized from the post above. – rony Jan 18 '18 at 12:27
this comes up, the same as I had before, Sir `undefined local variable or method rangeRounded` – rony Jan 18 '18 at 12:33
Made some chages. Try it again – Mikhail Katrin Jan 18 '18 at 12:35
it's even come up with weird error `undefined method id`, even the attributes :id I have explicitly mentioned. – rony Jan 18 '18 at 12:39
It will be much easier to figure out if you provide model and controller code – Mikhail Katrin Jan 18 '18 at 12:40
Hello, sir, I get resolved with this code render json: models, scope: { 'range': @rangeRounded } – rony Jan 18 '18 at 12:51

Pass variable from Controller to Serializer in Rails

1 Answers1