I have 2 models. Report and Server that have a belongs_to and has_many relationship. I created an accessor method using delegate that allows a Report to find its associated Server.company_id. Now, I want to run a query on Report that allows me to find all Report that are associated with a specific Server that has a specific company_id attribute of 5.
Here are my two models. And yes I know the current query wont work since Report does not have an attribute company_id.
And no, I dont want to store company_id inside of Report since that information doesn't belong in Report.
Report
class Report < ActiveRecord::Base
belongs_to :server
delegate :company_id, :to => :server
class << self
def method(url, base_url)
#Report.where(company_id: 5)
end
end
end
Server
class Server < ActiveRecord::Base
attr_accessible :company_id
has_many :reports
end
You can perform a query like this:
Report.joins(:servers).where(:servers => {:company_id => 5})
To me, this is the cleaner solution to raw SQL.
I'm using Rails 4.1.7 and the accepted answer did not work for me. What did work is
Report.joins(:server).where(:servers => {:company_id => 5})
Note that the difference is the key in the where clause is pluralized (:servers instead of :server)
This should do the trick
Report.joins(:server).where('servers.company_id = ?', 5)
you could also add a scope for this like so
scope :with_company_id, lambda {|id| joins(:server).where('servers.company_id = ?', id) }
and then write
Report.with_company_id(5)
This maybe an overkill but we have Arel:
# Get the SQL
# arelise will return the SQL (string)
def arelise(company_id)
# Tables to query
reports = Report.arel_table # Main table
servers = Server.arel_table.alias('servers')
reports
.join(servers, Arel::Nodes::InnerJoin).on(reports[:server_id].eq(servers[:id]))
.where(servers[:company_id].eq(company_id))
# Select all (*)
.project(reports[Arel.star])
.to_sql
end
sql = arelise(1)
# puts sql
# To Execute:
reports = Report.find_by_sql(sql)
# puts reports
Related
Given the following models:
class Client < ApplicationRecord
has_many :preferences
validates_associated :preferences
accepts_nested_attributes_for :preferences
end
class Preference < ApplicationRecord
belongs_to :client
validates_uniqueness_of :block, scope: [:day, :client_id]
end
I'm still able to create preferences with duplicate days* when creating a batch of preferences during client creation. This is (seemingly) because the client_id foreign key isn't available when the validates_uniqueness_of validation is run. (*I have an index in place which prevents the duplicate from being saved, but I'd like to catch the error, and return a user friendly error message, before it hits the database.)
Is there any way to prevent this from happening via ActiveRecord validations?
EDIT: This appears to be a known issue.
There's not a super clean way to do this with AR validations when you're batch inserting, but you can do it manually with the following steps.
Make a single query to the database using a Postgresql VALUES list to load any potentially duplicate records.
Compare the records you are about to batch create and pull out any duplicates
Manually generate and return your error message
Step 1 looks a little like this
# Build array of uniq attribute pairs we want to check for
uniq_attrs = new_collection.map do |record|
[
record.day,
record.client_id,
]
end
# santize the values and create a tuple like ('Monday', 5)
values = uniq_attrs.map do |attrs|
safe = attrs.map {|v| ActiveRecord::Base.connection.quote(v)}
"( #{safe.join(",")} )"
end
existing = Preference.where(%{
(day, client_id) in
(#{values.join(",")})
})
# SQL Looks like
# select * from preferences where (day, client_id) in (('Monday',5), ('Tuesday', 3) ....)
Then you can take the collection existing and use it in steps 2 and 3 to pull out your duplicates and generate your error messages.
When I've needed this functionality, I've generally made it a self method off my class, so something like
class Preference < ApplicationRecord
def self.filter_duplicates(collection)
# blah blah blah from above
non_duplicates = collection.reject do |record|
existing.find do |exist|
exist.duplicate?(record)
end
end
[non_duplicates, existing]
end
def duplicate?(record)
record.day == self.day &&
record.client_id = self.client_id
end
end
I made a real basic github project here that demonstrates the issue. Basically, when I create a new comment, it is saved as expected; when I update an existing comment, it isn't saved. However, that isn't what the docs for :autosave => true say ... they say the opposite. Here's the code:
class Post < ActiveRecord::Base
has_many :comments,
:autosave => true,
:inverse_of => :post,
:dependent => :destroy
def comment=(val)
obj=comments.find_or_initialize_by(:posted_at=>Date.today)
obj.text=val
end
end
class Comment < ActiveRecord::Base
belongs_to :post, :inverse_of=>:comments
end
Now in the console, I test:
p=Post.create(:name=>'How to groom your unicorn')
p.comment="That's cool!"
p.save!
p.comments # returns value as expected. Now we try the update case ...
p.comment="But how to you polish the rainbow?"
p.save!
p.comments # oops ... it wasn't updated
Why not? What am I missing?
Note if you don't use "find_or_initialize", it works as ActiveRecord respects the association cache - otherwise it reloads the comments too often, throwing out the change. ie, this implementation works
def comment=(val)
obj=comments.detect {|obj| obj.posted_at==Date.today}
obj = comments.build(:posted_at=>Date.today) if(obj.nil?)
obj.text=val
end
But of course, I don't want to walk through the collection in memory if I could just do it with the database. Plus, it seems inconsistent that it works with new object but not an existing object.
Here is another option. You can explicitly add the record returned by find_or_initialize_by to the collection if it is not a new record.
def comment=(val)
obj=comments.find_or_initialize_by(:posted_at=>Date.today)
unless obj.new_record?
association(:comments).add_to_target(obj)
end
obj.text=val
end
I don't think you can make this work. When you use find_or_initialize_by it looks like the collection is not used - just the scoping. So you are getting back a different object.
If you change your method:
def comment=(val)
obj = comments.find_or_initialize_by(:posted_at => Date.today)
obj.text = val
puts "obj.object_id: #{obj.object_id} (#{obj.text})"
puts "comments[0].object_id: #{comments[0].object_id} (#{comments[0].text})"
obj.text
end
You'll see this:
p.comment="But how to you polish the rainbow?"
obj.object_id: 70287116773300 (But how to you polish the rainbow?)
comments[0].object_id: 70287100595240 (That's cool!)
So the comment from find_or_initialize_by is not in the collection, it outside of it. If you want this to work, I think you need to use detect and build as you have in the question:
def comment=(val)
obj = comments.detect {|c| c.posted_at == Date.today } || comments.build(:posted_at => Date.today)
obj.text = val
end
John Naegle is right. But you can still do what you want without using detect. Since you are updating only today's comment you can order the association by posted_date and simply access the first member of the comments collection to updated it. Rails will autosave for you from there:
class Post < ActiveRecord::Base
has_many :comments, ->{order "posted_at DESC"}, :autosave=>true, :inverse_of=>:post,:dependent=>:destroy
def comment=(val)
if comments.empty? || comments[0].posted_at != Date.today
comments.build(:posted_at=>Date.today, :text => val)
else
comments[0].text=val
end
end
end
We are using thinkingtank gem and having trouble indexing model associations, even simple ones. For example, a profile belongs to an institution, which has a name – we would like to do something like:
class Profile < ActiveRecord::Base
#model associations
define_index do
indexes institution(:name), :as => :institution_name
end
end
but that doesn't work. This must be very simple – what am I doing wrong?
a possible solution to this issue would be adding a method returning the element to index. For the profile.institution.name case:
# profile.rb
# ...
belongs_to :institution
# ...
define_index do
indexes institution_name
end
def institution_name
self.institution.name
end
# ...
Also the ", :as => ..." syntax is not supported on thinkingtank.
I would also recommend giving a try to Tanker: https://github.com/kidpollo/tanker
Regards.
Adrian
I've read this article, but it's for Rails 1.x.
I'd really like to create my own association methods:
user = User.find(1)
# Example of a normal association method
user.replies.create(:body => 'very informative. plz check out my site.')
# My association method
user.replies.find_by_spamminess(:likelihood => :very)
In Rails 3, what's the proper way of doing this?
The Rails 3 way of doing things is often to not use find methods, but rather scopes, which delays the actual database call until you start iterating over the collection.
Guessing at your first example, I would do:
in class Reply ...
scope :spaminess, lambda {|s| where(:likelyhood => s) }
and then using it:
spammy_messages = user.replies.spaminess(:very)
or to use it in a view
spammy_messages.each do |reply|
....
end
I think I found it!
If you search for "association extensions" the Rails API page for ActiveRecord::Assications, you'll see that this is the syntax (copied from that link):
class Account < ActiveRecord::Base
has_many :people do
def find_or_create_by_name(name)
first_name, last_name = name.split(" ", 2)
find_or_create_by_first_name_and_last_name(first_name, last_name)
end
end
end
I have a MailingList model that has_may :people
For most of my application, I only want to get people that are active
So #mailing_list.people should only return people that are active
In my model, I can't do
def people
self.people.find_all{ |p| !p.activated_at.nil? }
end
because that keeps calling itself. What is the ruby/rails way to automatically filter the people. Another possible issue is that I think self.people returns an array of active record objects where self.people.find_all... will return an array. This will cause some of my code to break. It's easy fixes but is there a way to return active record objects? It would be nice to have the option.
Thanks!
This is a perfect example for a named scope:
class Person < ActiveRecord::Base
named_scope :active, :conditions => 'activated_at is not null'
end
Then just call it:
# equivalent to Person.find(:all, :conditions => 'activated_at is not null')
#active_people = Person.active
You can also filter at the association level.
has_many :people, :conditions => {:activated => true}
You can used the standard find method or a dynamic finder. Your find might read as follows:
people.find(:all, :conditions => "activated_at = nil")
OR
people.find_all(:conditions => "activated_at = nil")
A dynamic version of this might read as:
people.find_by_activated_at(nil)