activerecord – Page 14

How do i work with two different databases in rails with active records?

June 4, 2023 by Tarik

Add new sections to your database.yml e.g. other_development: adapter: mysql database: otherdb_development username: root password: host: localhost other_production: adapter: mysql database: otherdb_production username: root password: host: localhost Add a class in lib/other_database.rb class OtherDatabase < ActiveRecord::Base establish_connection “other_#{RAILS_ENV}” end and then for each model which isn’t in the default database subclass from OtherDatabase e.g.: class … Read more

Why polymorphic association doesn’t work for STI if type column of the polymorphic association doesn’t point to the base model of STI?

June 1, 2023 by Tarik

Good question. I had exactly the same problem using Rails 3.1. Looks like you can not do this, because it does not work. Probably it is an intended behavior. Apparently, using polymorphic associations in combination with Single Table Inheritance (STI) in Rails is a bit complicated. The current Rails documentation for Rails 3.2 gives this … Read more

Finding nil has_one associations in where query

June 1, 2023 by Tarik

It’s quite common task, SQL OUTER JOIN usually works fine for it. Take a look here, for example. In you case try to use something like not_purchased_items = Item.joins(“LEFT OUTER JOIN purchases ON purchases.item_id = items.id”).where(“purchases.id IS null”)

Possible to specify unique index with NULLs allowed in Rails/ActiveRecord?

May 31, 2023 by Tarik

Your migration will work and will allow multiple null values (for the most database engines). But your validation for the user class should look like below. validates :email, uniqueness: true, allow_nil: true

Rails includes with scope

May 31, 2023 by Tarik

I think the best solution would be: Author.includes(:articles).where(:articles=>{published: true}).find(params[:author_id]) Or you can create scope: class Author < ActiveRecord::Base scope :with_published_articles, -> { includes(:articles).where(articles: { published: true}) } end and then: Author.with_published_articles.find(params[:author_id].to_s)

Rails: Is it bad to have an irreversible migration?

May 31, 2023 by Tarik

If you are dealing with production-grade systems then yes, it is very bad. If it is your own pet project, then anything is allowed (if nothing else, it will be a learning experience 🙂 though chances are that sooner rather than later, even in a pet project, you will find yourself having put a cross … Read more

hash[‘key’] to hash.key in Ruby

May 29, 2023 by Tarik

>> require ‘ostruct’ => [] >> foo = {‘bar’=>’baz’} => {“bar”=>”baz”} >> foo_obj = OpenStruct.new foo => #<OpenStruct bar=”baz”> >> foo_obj.bar => “baz” >>

Error Handling in ActiveRecord Transactions?

May 28, 2023 by Tarik

If you are using the save! method with a bang (exclamation point), the application will throw an exception when the save fails. You would then have to catch the exception to handle the failure. begin @ticket.transaction do @ticket.save! @user.save! end #handle success here rescue ActiveRecord::RecordInvalid => invalid #handle failure here end

How to get the latest record from each group in ActiveRecord?

May 27, 2023 by Tarik

Postgres In Postgres, this can be achieved with the following query. SELECT DISTINCT ON (“group”) * FROM projects ORDER BY “group”, date DESC, id DESC Because the date column might not be unique here, I have added an additional ORDER BY clause on id DESC to break ties in favor of the record with the … Read more

Rails ActiveRecord Query Date Range

May 26, 2023 by Tarik

Should be: @due_this_week = current_user.tasks.where(due_date: 1.week.ago..Date.today)