Storing and Retrieving postgres nested JSONB data type in rails form

Question

I realised there is not much information about how to use rails form to store and retrieve JSON type data. I am currently facing the following problem:

I have a form that creates a nested structure in JSON:

= form_for(@car) do |cf|
    = cf.fields_for :locations do | locations_f |
        = locations_f.fields_for :primary_location do | primary_location_f |
            .sm-col.md-col.sm-col-6.px2
                label.inline-block.mb1 District
                = primary_location_f.text_field :district 
            .sm-col.md-col.sm-col-6.px2
                label.inline-block.mb1 Street
                = primary_location_f.text_field :street

It will generate input HTML tags as such:

<input name="car[locations][primary_location][district]">

<input name="car[locations][primary_location][street]">

I am able to persist it in database after doing params.permit:

params.require(:car).permit([
    locations:[primary_location:[:street, :district]]
])

I also create store_accessor in the model

store_accessor :locations, :primary_location, :other_locations

However, after I persisted the data, I want it to be shown in the text_field what is already persisted in the database. I try to do something like:

= primary_location_f.text_field :district, value: @car.locations['primary_location']['district']

However, it will run into NilClass Error as sometimes @car.locations['primary_location'] may be nil, and error will arise when I call @car.locations['primary_location']['district'].

I wonder what is the best way to store and retrieve JSON data type. And what is a good way when the JSON is nested.

Thanks

Uzbekjon · Accepted Answer · 2016-05-21 17:21:51Z

1

However, it will run into NilClass Error as sometimes @car.locations['primary_location'] may be nil, and error will arise when I call @car.locations['primary_location']['district'].

Use .try() method.

@car.locations.try(:[],:primary_location).try(:[], :district)

I wonder what is the best way to store and retrieve JSON data type. And what is a good way when the JSON is nested.

I prefer built in JSON store. Similar to what you are using.

edited May 21, 2016 at 17:21

answered May 21, 2016 at 13:31

Uzbekjon

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3 Comments

Chris Yeung Over a year ago

Hi how would you use store to achieve it? How can it retrieve the data to the form?

Uzbekjon Over a year ago

The form simply calls accessors to your fields, so just add corresponding store_accessors. As for json with levels deeper than 1 I would write loops in the view.

Chris Yeung Over a year ago

Thanks. Will you be able to write an example to help me understand better? Thanks!

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