ruby on rails jsonb column default value

Question

I have a model ProjectKeyword where I use jsonb datatype in the column :segemnted_data

class ProjectKeyword < ApplicationRecord   belongs_to :project   belongs_to :keyword   has_many :project_keyword_dimensions   has_many :dimensions, through: :project_keyword_dimensions    validates :project_id, :keyword_id, presence: true end 

Migration

class AddSegemtnedDataToProjectKeywords < ActiveRecord::Migration[5.0]   def change     add_column :project_keywords, :segmented_data, :jsonb, default: '{}'     add_index  :project_keywords, :segmented_data, using: :gin   end end 

My problem is when I create new project_keyword instance the default value of the segmented_data is a string not a hash and I cannot update this field or merge with another hash For example

[12] pry(#)> new_pr_keyword = ProjectKeyword.new(project_id: 1671333, keyword_id: 39155) => #<ProjectKeyword:0x007fd997641090 id: nil, project_id: 1671333, keyword_id: 39155, segmented_data: "{}"> [13] pry(#)> new_pr_keyword.save! => true [14] pry(#)> new_pr_keyword.segmented_data.update({'new_data' => 'some_data'}) NoMethodError: undefined method `update' for "{}":String from (pry):14:in `block (3 levels) in <top (required)>' 

But when I asign hash value to the field segmented_data before update then update method works fine.

For example

[15] pry(#)> new_pr_keyword.segmented_data = {'new_data' => 'some_data'} => {"new_data"=>"some_data"} [16] pry(#)> new_pr_keyword.save! => true [17] pry(#)> new_pr_keyword.segmented_data.update({'new_data_2' => 'some_data_2'}) => {"new_data"=>"some_data", "new_data_2"=>"some_data_2"} [18] pry(#)> new_pr_keyword.save! => true 

The question is how to make default value of segmented_data to be a Hash class not a String so method update then will work straight away on this field, after object just was created.

Answer 1

This has worked for me on several projects:

add_column :project_keywords, :segmented_data, :jsonb, default: {} 

(not a string, a ruby hash)

I seem to recall this not working on Rails 3, but it should be fine in Rails 4.