Rails 4, nested attributes, strong parameters & JSON

Question

Rails 4, basic JSON API - I am tying to update Status object with association Position objects.

Job Status model:

class JobStatus < ActiveRecord::Base

    belongs_to :job
    has_many :positions

    accepts_nested_attributes_for :positions, limit: 1

    validates :job_id,
                    :slug,
                    presence: true

end

Position Model:

class Position < ActiveRecord::Base
  belongs_to :agent
  belongs_to :job_status

  validates :job_status_id,
                    :agent_id,
                    :lat,
                    :lng,
                    presence: true

end

Job Statuses Controller:

class Api::V1::Jobs::JobStatusesController < ApplicationController

    wrap_parameters format: [:json]

    def create

        @status = JobStatus.new(status_params)

        @status.job_id = params[:job_id]

        @status.positions.build

        if @status.save
            render :json => {status: 'success', saved_status: @status}.to_json
        else
            render :json => {status: 'failure', errors: @status.errors}.to_json
        end

    end

    private

        def status_params
            params.permit(:job_id, :slug, :notes, :positions_attributes => [:lat, :lng, :job_status_id, :agent_id])
        end

end

This is the JSON I am posting:

{
  "slug":"started",
  "notes":"this xyz notes",
  "positions_attributes":[{
    "lat" : "-72.348596",
    "lng":"42.983456"
  }]
}

When I do "logger.warn params" immediately above the @status.positions.build:

{"slug"=>"started", "notes"=>"this xyz notes", "positions_attributes"=>[{"lat"=>"-72.348596", "lng"=>"42.983456"}], "action"=>"create", "controller"=>"api/v1/jobs/job_statuses", "job_id"=>"3", "job_status"=>{"slug"=>"started", "notes"=>"this xyz notes"}}

And the error message that gets returned to me:

{
"status":"failure",
"errors":{
"positions.job_status_id":[
"can't be blank"
],
"positions.agent_id":[
"can't be blank"
],
"positions.lat":[
"can't be blank"
],
"positions.lng":[
"can't be blank"
]
}

So I'm not really sure where my problem is - are my strong parameters not allowed correctly? Should I be posting an array of positions because it's a has_many relationship, even though I only want to create one at a time? Am I not using .build correctly? I've playing monkeying around with all of these, but not luck - I'm pretty sure there's something obvious I am just not seeing.

Also, if anyone has a way to log output the data from wherever the problem is coming from, that would be v. helpful in the future.

San San · Accepted Answer · 2014-07-11T14:09:48

Your problem is this line:

@status.positions.build

This is only required in the new method to build HTML form, which is obviously not applicable in this case. This method is actually blanking out all position parameters that you are posting.

Removing this line will fix your issue.

Rails 4, nested attributes, strong parameters & JSON

1 Answers