Appending data to JSON column - Rails 4, Postgres

Question

Model Listing has a json column named vendors, which defaults to {}:

add_column :listings, :vendors, :json, null: false, default: {
  hd: {}
  ...
  }
end

Inside the Listing class, I am trying to merge! in a hash to hd: {..} like so:

def self.append_vendor_attrs(sku)
  listing = find_by(sku: sku) || Listing.new(sku: sku)
  listing.vendors[:hd].merge!({ foo: 'bar' })
  listing.vendors_will_change!
  listing.save! # throws no exceptions in the log
end

but vendors[:hd] remains empty. if I try to replicate this manually with:

l = Listing.create... 
l.vendors[:hd].merge!({ foo:'bar' })

my hash persists.

Have you tried moving listing.vendors_will_change! above the line where you modify the attribute in place? My hunch is that the code you have in your method tells AR that the value of the attribute was the new value, so that it doesn't see the object as dirty when you call save!. — hoffm
– hoffm, Commented Jan 5, 2017 at 14:59
@hoffm of course! I was calling will_change after the data was already appended, triggering AR to "listen" to any changes to that row but nothing was changed. Go Brooklyn! Turn this into an answer so I can accept? — dimitry_n
– dimitry_n, Commented Jan 5, 2017 at 16:21

hoffm · Accepted Answer · 2017-01-05 21:55:27Z

1

Calling listing.vendors_will_change! tells Active Record that the value of the attribute "was" the new value. From AR's perspective, then, the old and new values match, and so the record is not dirty when you call save!.

The fix is to move listing.vendors_will_change! above the line where you modify the attribute. So the new code will look like this:

def self.append_vendor_attrs(sku)
  listing = find_by(sku: sku) || Listing.new(sku: sku)
  listing.vendors_will_change!
  listing.vendors[:hd].merge!({ foo: 'bar' })
  listing.save! # throws no exceptions in the log
end

answered Jan 5, 2017 at 21:55

hoffm

2,43624 silver badges36 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Appending data to JSON column - Rails 4, Postgres

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related