I'm at a loss. We have two classes, Sample and Workflow, that have a many-to-many relationship, using has_many, :through.
At Rails Console, I get the following:
[3] pry(main)> s = Sample.find(1)
Sample Load (0.2ms) SELECT `samples`.* FROM `samples` WHERE `samples`.`id` = 1 LIMIT 1
=> #<Sample id: 1, name: "Some sample", experiment_type: "Some type", category_id: nil,
created_at: "2014-01-14 21:24:14", updated_at: "2014-01-14 21:24:14">
[4] pry(main)> wf = Workflow.new
=> #<Workflow id: nil, name: nil, description: nil>
[5] pry(main)> wf.samples.include?(s)
Sample Exists (0.2ms) SELECT 1 AS one FROM `samples` INNER JOIN `sample_workflows` ON
`samples`.`id` = `sample_workflows`.`sample_id` WHERE `sample_workflows`.`workflow_id` IS NULL
AND `samples`.`id` = 1 LIMIT 1
=> true
[6] pry(main)> wf.samples
=> []
[7] pry(main)> wf.samples.include?(s)
=> false
wf is a brand new workflow, should not have any samples attached to it. wf.samples.include? indicates that sample 1 is already linked to the workflow. But if I try to look at the samples, the array comes back blank, and further include? queries return false (as they should). The same thing happens for sample 2, but not for any others I've tried. Is there some way I could have made the workflow link to two samples by default by mistake?
Related
I have created a Ruby on Rails job (extending from ActiveJob::Base) that parses a CSV file and inserts its rows as records (Students) in a database. That is working as expected.
However, when I try to fetch another object from the DB (the Career for each Student, which is part of each CSV row as a pair (career_code, career_name)), I'm getting this error:
undefined method 'find_by' for Career:Class
(I have also tried using Career.where instead).
I find this quite strange, since I'm already saving my Student, which is also an ActiveRecord::Base child class.
Here's the relevant part of my job:
ActiveRecord::Base.transaction do
student_hash.keys.each do |k|
some_student = student_hash[k]
student = Student.new
student.csv_id = some_student.id
student.first_name = some_student.first_name
student.last_name = some_student.last_name
student.file_number = some_student.file_number
# student.career = Career.where(code: some_student.career_code)
student.career = Career.find_by code: some_student.career_code
puts student.save! # Why this works, and the above line doesn't?
end
end
And also, the desired output, as I can see it in the Rails console:
Loading development environment (Rails 4.2.4.rc1)
2.1.3 :001 > Career.where(code: 11)
Career Load (0.5ms) SELECT "careers".* FROM "careers" WHERE "careers"."code" = ? [["code", 11]]
=> #<ActiveRecord::Relation [#<Career id: 4, name: "Informática", created_at: "2015-09-30 22:05:07", updated_at: "2015-09-30 22:05:07", code: 11>]>
2.1.3 :002 > Career.where code: 11
Career Load (0.2ms) SELECT "careers".* FROM "careers" WHERE "careers"."code" = ? [["code", 11]]
=> #<ActiveRecord::Relation [#<Career id: 4, name: "Informática", created_at: "2015-09-30 22:05:07", updated_at: "2015-09-30 22:05:07", code: 11>]>
2.1.3 :003 > Career.find_by code: 11
Career Load (0.4ms) SELECT "careers".* FROM "careers" WHERE "careers"."code" = ? LIMIT 1 [["code", 11]]
=> #<Career id: 4, name: "Informática", created_at: "2015-09-30 22:05:07", updated_at: "2015-09-30 22:05:07", code: 11>
2.1.3 :004 >
Probably this is a really stupid question, but I'm quite a beginner using Rails. Do I need to import some sort of "Context" (this seems unlikely, since Student seems to be properly resolved)? I'm using Rails 4.2.4.rc1 by the way.
Thanks in advance
Any chance at that point in the code Career isn't an AR, but some other class? That would at least explain why the methods don't exist.
I start to using pry in a rails console.
When I get a instance of a Rails model, the values are shown without line breaks like this:
pry(#<Class:0x1022f60e0>):1> first
=> #<Article id: 1, name: "What is Music", content: "Music is an art form in which the medium is sound o...", created_at: "2011-08-24 20:35:29", updated_at: "2011-08-24 20:37:22", published_at: "2011-05-13 23:00:00">
from http://railscasts.com/episodes/280-pry-with-rails?view=asciicast
Is there way to show the values with line breaks like this?
Article
id: 1
name: "What is Music"
content: "Music is an art form in which the medium is sound o..."
created_at: "2011-08-24 20:35:29"
updated_at: "2011-08-24 20:37:22"
published_at: "2011-05-13 23:00:00"
You could call .to_yaml on the model instance! It returns a string that's formatted almost exactly like you're requesting it to be.
Here are some examples of to_yaml output:
http://yaml4r.sourceforge.net/doc/page/examples.htm
I would recommend that you install awesome_print.
Add it to your Gemfile:
group :development do
gem 'awesome_print'
end
And install it with bundle install.
Now use ap to print it in the console:
pry(#<Class:0x1022f60e0>):1> ap first
#<Article:0x1022f60e0> {
:id => 1,
:name => "What is Music"
:content => "Music is an art form in which the medium is sound o..."
:created_at => "2011-08-24 20:35:29"
:updated_at => "2011-08-24 20:37:22"
:published_at => "2011-05-13 23:00:00"
}
I think, the below trick will work for you.
arup#linux-wzza:~/Rails/model_prac> rails c
Loading development environment (Rails 4.1.4)
2.1.2 :001 > Comment.first
Comment Load (0.4ms) SELECT "comments".* FROM "comments" ORDER BY "comments"."id" ASC LIMIT 1
=> #<Comment id: 1, value_old: "I am a good Boy.", value_new: "I am a bad Boy.", created_at: "2014-08-02 17:36:14", updated_at: "2014-08-02 18:21:42">
2.1.2 :002 > y Comment.first
Comment Load (0.4ms) SELECT "comments".* FROM "comments" ORDER BY "comments"."id" ASC LIMIT 1
--- !ruby/object:Comment
attributes:
id: 1
value_old: I am a good Boy.
value_new: I am a bad Boy.
created_at: 2014-08-02 17:36:14.249466000 Z
updated_at: 2014-08-02 18:21:42.511522000 Z
=> nil
2.1.2 :003 >
I run into a weird issue since I upgraded to Rails 3.2.
My application have some objects managed with nested_forms, but when i try to reach a collection's size after having built a new nested object, the nested object is taken in count.
For ex.:
1.9.3p0 :004 > e = Expense.last
Expense Load (22.6ms) (...)
=> #<Expense id: 1, (...)
1.9.3p0 :005 > e.comments.size
(0.3ms) SELECT COUNT(*) (...)
=> 0
1.9.3p0 :006 > e.comments.build
=> #<Comment id: nil, content: nil, commentable_id: 1, commentable_type: "Expense", created_at: nil, updated_at: nil, creator_id: nil>
1.9.3p0 :007 > e.comments.size
=> 1
In this case, I expect the e.expense.size to return 0 since the Commentobject has not been saved yet.
Building the comment creates ... 1 comment. It doesn't exist in the database (yet) so e.commment.count would return 0, but it exists in the application, so size returns 1. So that sort of makes sense.
But I do see there's a little potentially unexpected result here. If a comment doesn't exist in memory, it looks like Rails checks with the DB (the SELECT COUNT(*)...), whereas if it finds one in memory it does not.
I wonder what would happen if you had several existing comments already, then checked e.comments.size in that case?
Which version of Rails were you coming from that worked differently?
It appears some of my seeds are not saving. For starters, I will show a console session so you can see that the 'instructor_id' is indeed being set in the console, but not when I seed.
ruby-1.9.2-p180 :015 > c = Course.find 2
Course Load (1.6ms) SELECT "courses".* FROM "courses" WHERE "courses"."id" = $1 LIMIT 1 [["id", 2]]
=> #<Course id: 2, name: "Microcomputers II Lab", course_code: "CE-420L", instructor_id: nil, school_id: nil, created_at: "2011-06-04 19:40:32", updated_at: "2011-06-04 19:40:32">
ruby-1.9.2-p180 :016 > c.instructor = Instructor.first
Instructor Load (0.6ms) SELECT "instructors".* FROM "instructors" LIMIT 1
=> #<Instructor id: 1, name: "Instructor Name", created_at: "2011-06-04 19:40:32", updated_at: "2011-06-04 19:40:32">
ruby-1.9.2-p180 :017 > c
=> #<Course id: 2, name: "Microcomputers II Lab", course_code: "CE-420L", instructor_id: 1, school_id: nil, created_at: "2011-06-04 19:40:32", updated_at: "2011-06-04 19:40:32">
From looking at the console, you can see that when I call c.instructor = Instructor.first, it is correctly setting my instructor_id.
Now, in the seeds file I have variables. (This is just a snippet)
### Instructors ###
puts "Creating Instructors"
instructor_1 = Instructor.find_or_create_by_name("Instructor Name")
### Courses ###
puts "Creating Courses"
ce420L = Course.find_or_create_by_name("Microcomputers II Lab", :course_code => "CE-420L")
### Add the Instructor to the Course ###
puts "Adding an Instructor to the Courses"
ce420L.instructor = instructor_1
But when I run the seeds using 'rake db:seed', it is correctly creating all of my models, and most of my relationships. But it is not setting the instructor properly.
Thoughts?
EDIT:
Just tried:
ce420 = Course.find_or_initialize_by_name("Microcomputers II")
ce420.instructor_id = instructor_1.id
ce420.save!
And it did not save my instructor.
Here are my models.
class Instructor < ActiveRecord::Base
### ASSOCIATIONS ###
has_many :courses
end
class Course < ActiveRecord::Base
belongs_to :instructor
end
Did you run...
ce420L.save!
... after assigning the instructor?
Much faster to do this:
### Courses ###
puts "Creating Courses belonging to Instructor 1"
ce420L = Course.find_or_initialize_by_name("Microcomputers II Lab") :course_code => "CE-420L")
ce420L.instructor_id = instructor_1.id
ce420L.save
Note the following:
You had an errant comma after your find_or_create on ce420L.
Doing the assignment together with the course creation prevents the system from validating and saving ce420L twice.
You can try assigning the specific ID as I did, i.e. ce420L.instructor_id = ...
If this doesn't work, check your Instructor Model to ensure you don't have any callbacks getting in the way.
I'm testing Rails 3 beta 4 on Ruby 1.9.2-head, and when I start a
console and do:
Game.first.to_sql
I get this error:
ArgumentError: wrong number of arguments (0 for 1)
I know it can find the Game record, because when I type:
Game.first
it returns:
=> #<Game id: 1, name: "Galaga", created_at: "2010-06-19 11:02:37",
updated_at: "2010-06-19 11:02:37">
What am I missing? I just want to make the to_sql work in a very simple
case.
.
When you run Game.first you are returning a Game object, not a ActiveRecord::Relation object as you are expecting.
To do what you're trying to do, you'll need to do:
Game.limit(1).to_sql
This lets you run it without to_sql and return the object as you expected it, although it will be in an array, which then you can run .first on it like you wanted anyways.
irb(main):004:0> Game.limit(1).to_sql
=> "SELECT `games`.* FROM `games` LIMIT 1"
irb(main):005:0> Game.limit(1).class
=> ActiveRecord::Relation
irb(main):006:0> Game.limit(1)
=> [#<Game id: 1, name: "Galaga", created_at: "2010-06-19 11:02:37", updated_at: "2010-06-19 11:02:37">]
irb(main):007:0> Game.limit(1).first
=> #<Game id: 1, name: "Galaga", created_at: "2010-06-19 11:02:37", updated_at: "2010-06-19 11:02:37">
When you dig into the source, when you run .first on an ActiveRecord::Relation it runs the following (which is the same as I showed you):
def find_first
if loaded?
#records.first
else
#first ||= limit(1).to_a[0]
end
end