JSON Attribute

json_attribute is a gem allows Ruby on Rails ActiveRecord model can use one column with jsonb or json type to generate many attributes. in this way, you can store many attributes into one column but manipulating them individually.

Installation

Install

• Add to gem file

gem 'json_attribute'

• Install required gems

$ bundle install

Add json_attribute column to the table of your model

• Create migration

# jsonb is only for PostgresSQL version >= 9.4
$ rails g migration add_json_attribute_to_[table] json_attribute:jsonb

# take json type if your version under 9.4
$ rails g migration add_json_attribute_to_[table] json_attribute:json

• Migrate database

$ rails db:migrate

Add has_json_attribute to your model

• Add to app/models/your_model.rb:

# app/models/your_mode.rb

class YourModel < ActiveRecord::Base
   has_json_attribute :attr_1
   has_json_attribute :attr_2, default: 'hello'
   has_json_attribute :attr_3, type: :string, allow_nil: true
end

• Your model has attr_1, attr_2, attr_3 attributes now. all of them will be save into json_attribute column.

Options for has_json_attribute

has_json_attribute attribute_name[, options]

the options as the following:

• type validates values must be a certain type before saving. can be :boolean, :integer, :float, :string. default value: nil (attribute can be value of any primitive type).

• default used to set attribute default value. this options can be lambda. for example, default: ->(record) { "#{record.fistr_name} #{record.last_name}" }. default value: nil

• presence validates value must be present. default value: nil

• column to determine which table column will be used to provide attributes. default value: :json_attribute

• allow_nil when type is set, this option can allow attribute to be nil.

Examples

class Model < ActiveRecord::Base
  has_json_attribute :attr_1
  has_json_attribute :attr_2, type: :string, default: 'hello'
  has_json_attribute :attr_3, type: :string, default: 'hello', allow_nil: true
  has_json_attribute :attr_4, presence: true, default: true
end

# set value
record = Model.new
record.attr_1 = 3.14
record.save!
record.attr_1 # => 3.14 

# attribute default value
record = Model.new
record.attr_2 # => 'hello'

# type casting before saving
record = Model.new
record.attr_2 = 123
record.attr_2 # => '123'

# allow nil for attribute with type
record = Model.new
record.attr_3 = nil
record.valid? # => true

# attribute must be present
record = Model.new
record.attr_4 = nil
record.valid? # => false

License

The gem is available as open source under the terms of the MIT License.