Rails supports Single Table Inheritance. From the AR docs: Active Record allows inheritance by storing the name of the class in a column that by default is named “type” (can be changed by overwriting Base.inheritance_column). This means that an inheritance looking like this: class Company < ActiveRecord::Base; end class Firm < Company; end class Client … Read more
Credits to http://moeffju.net/blog/using-bigint-columns-in-rails-migrations class CreateDemo < ActiveRecord::Migration def self.up create_table :demo, :id => false do |t| t.integer :id, :limit => 8 end end end See the option :id => false which disables the automatic creation of the id field The t.integer :id, :limit => 8 line will produce a 64 bit integer field
This is because attributes/associations are actually methods(getters/setters) and not local variables. When you state “parent = value” Ruby assumes you want to assign the value to the local variable parent. Somewhere up the stack there’s a setter method “def parent=” and to call that you must use “self.parent = ” to tell ruby that you … Read more
By default you’ll only get the JSON that represents modelb in your example above. But, you can tell Rails to include the other related objects as well: def export @export_data = ModelA.find(params[:id]) respond_to do |format| format.html format.json { render :json => @export_data.to_json(:include => :modelb) } end end You can even tell it to exclude certain … Read more
In Rails 3.1 you can just class Form < ActiveRecord::Base serialize :column, JSON end
where(‘archived IS NOT NULL’, null, false)
Bah, found it here: https://stackoverflow.com/a/5570221/417872 City.includes(:photos).where(photos: { city_id: nil })
Rails 6 Rails 6 added an upsert and upsert_all methods that deliver this functionality. Model.upsert(column_name: value) [upsert] It does not instantiate any models nor does it trigger Active Record callbacks or validations. Rails 5, 4, and 3 Not if you are looking for an “upsert” (where the database executes an update or an insert statement … Read more
You can convert an array of objects arr to an ActiveRecord::Relation like this (assuming you know which class the objects are, which you probably do) MyModel.where(id: arr.map(&:id)) You have to use where though, it’s a useful tool which you shouldn’t be reluctant to use. And now you have a one-liner converting an array to a … Read more
1) To get Projects with at least 1 vacancy: Project.joins(:vacancies).group(‘projects.id’) 2) To get Projects with more than 1 vacancy: Project.joins(:vacancies).group(‘projects.id’).having(‘count(project_id) > 1’) 3) Or, if Vacancy model sets counter cache: belongs_to :project, counter_cache: true then this will work, too: Project.where(‘vacancies_count > ?’, 1) Inflection rule for vacancy may need to be specified manually?