activerecord

问题 There's a named_scope in a project I'm working on that looks like the following: # default product scope only lists available and non-deleted products ::Product.named_scope :active, lambda { |*args| Product.not_deleted.available(args.first).scope(:find) } The initial named_scope makes sense. The confusing part here is how .scope(:find) works. This is clearly calling another named scope (not_deleted), and applying .scope(:find) afterwards. What/how does .scope(:find) work here? 回答1: A quick

问题 There's a named_scope in a project I'm working on that looks like the following: # default product scope only lists available and non-deleted products ::Product.named_scope :active, lambda { |*args| Product.not_deleted.available(args.first).scope(:find) } The initial named_scope makes sense. The confusing part here is how .scope(:find) works. This is clearly calling another named scope (not_deleted), and applying .scope(:find) afterwards. What/how does .scope(:find) work here? 回答1: A quick

问题 I want to find all records, say Posts, created today with Ruby on Rails, then all Posts created yesterday, and so on… how should I do? Thank you, Kevin 回答1: Try this: #Today Posts.find(:all, conditions: { :created_at => Date.today...Date.today + 1 }) #Yesterday Posts.find(:all, conditions: { :created_at => Date.today - 1...Date.today }) Or this (preferable, in my opinion): #Today Posts.find(:all, conditions: ["DATE(created_at) = ?", Date.today] ) #Yesterday Posts.find(:all, conditions: ["DATE

问题 I'd like to select posts that have one or more comments using Rails 3 and a single query. I'm trying something like this: Post.includes(:comments).where('count(comments.id)>0') However I get this error: ActiveRecord::StatementInvalid: PGError: ERROR: aggregates not allowed in WHERE clause I've googled this and similar approaches, group by, etc with no luck. Any help will be appreciated. 回答1: I'm sure you may have figured this out by now, but I believe what you're looking for is the having(

问题 I am using Ruby on Rails 4 and I would like to properly handle the updating and creating process of associated records through the update_attributes method. That is, I have the following: # Model class Article < ActiveRecord::Base has_many :categories accepts_nested_attributes_for :categories end # Controller class ArticlesController < ApplicationController def update @article = Article.find(params[:id]) @article.update_attributes(update_params) ... end private def update_params params

问题 I have a User model which has_many experiments: class User < ActiveRecord::Base has_many :experiments, :dependent => :destroy and Experiment model: class Experiment < ActiveRecord::Base belongs_to :user has_attached_file :thumbnail I want to hook for destroy moment at the Experiment model after the owner User get destroyed. (ex user cancel his account) I need to do so to delete the attachment image of the Experiment model, which is stored at amazon. like experiment.thumbnail.destroy What is

问题 I'm trying to give admins of my web application the ability to add some new fields to a model. The model is called Artwork and i would like to add, for instante, a test_column column at runtime. I'm just teting, so i added a simple link to do it, it will be of course parametric. I managed to do it through migrations: def test_migration_create Artwork.add_column :test_column, :integer flash[:notice] = "Added Column test_column to artworks" redirect_to :action => 'index' end def test_migration

问题 Im having troubles with awesome Globalize3 gem. For now I`m having two languages :en and :ru. And :ru falls back to :en like this #/config/initializers/globalize.rb Globalize.fallbacks = {:ru => [:ru, :en]} In my controller I am trying to sort the whole collection of translated records either by name translations or by translations fallback values. But with_translations() does not seem to give me such opportunity! Country.with_translations(:ru).order('country_translations.name ASC') #this

问题 I have two models Album.rb class Album < ActiveRecord::Base has_many :tracks self.table_name = 'prefix_album' end Track.rb class Track < ActiveRecord::Base belongs_to :album self.table_name = 'prefix_track' end Now, because reasons, the table names are prefixed, so I have prefix_album and prefix_track tables in my database. For basic use, it works fine. Now the problem with the following query : Album.joins(:tracks).where(tracks: { id: [10, 15] }) Results in the following SQL : SELECT * FROM

问题 I'd like to use the rank() function PostgreSQL on one of my columns. Character.select("*, rank() OVER (ORDER BY points DESC)") But since I don't have a rank column in my table rails doesn't include it with the query. What would be the correct way to get the rank included in my ActiveRecord object? 回答1: try this: Character.find_by_sql("SELECT *, rank() OVER (ORDER BY points DESC) FROM characters") it should return you Character objects with a rank attribute, as documented here . However, this