Scenario: I have a quiz type setup where Questions have many Answers and also have a Response provided by the user (omitted). A response has a selected attribute to indicate the user's choice and a correct? method that compares selected with the correct_answer.
Code: is here in this GitHub repo, along with seed data. Quick links to:
Question.rb
Answer.rb
Response.rb
Problem: I want to return all responses for a question that are correct however, unsaved records are not included.
I've tried a couple of different ways, as you'll see in the code including scope, question.correct_responses and also inverse_of (which I've read is supposed to be automatic now) - but to no avail.
Basically, I'm expecting following code to return 1, not 0.
q=Question.first
r=q.responses.build
r.selected = q.correct_answer
q.responses.correct.size # => 0??! wtf man!?
Your assistance is greatly appreciated.
When you use a scope you're going to the database.
Since you aren't saving the response, you don't want to go to the database. Instead, you should use something like the line below, which will select all of the question's "correct" responses and then count them.
q.responses.select { |r| r.correct? }.size
EDIT: or the short syntax for select:
q.responses.select(&:correct?).size
Related
I am pretty new in rails and honestly, I am struggling with queries even after multiple researchs.
Here is my simple schema:
So basically, a question has many options, an option belongs to a question and has many answer, and an answer belongs to an option and has many users.
I don't think it s necessary to post the models code since it is just like i mentioned above.
What i would like to do is given a question option, see if a particular user already checked it (so look in the answer table if there is a row matching a given id_option, user_id and user_type). So in my haml loop, when displaying the different question option, i'm calling a method of my question_option model just like this :
- question.question_option.all.each do |option|
#{option.title}
.check
- if option.selected_by(current_actor)
= check_box_tag(option.id, "checked",true, class: 'styled-checkbox')
- else
= check_box_tag(option.id, "checked",false, class: 'styled-checkbox')
and the method called :
def selected_by(answerer)
answer_match =
::Vacancies::QuestionOption
.joins(:answers)
.where(answerer_id: answerer.id, answerer_type:answerer.type )
response = answer_match.find(self.id)
return response
end
This method is located in my QuestionOption model and leads to no errors but it s not working ever.
Can you help me transform this query to make it work with ActiveRecord ? Thanks
Try the below code. It checks if there are any answers by the user passed in the params on the question. I think this is what you intended to do as well-
def selected_by(answerer)
answers =
Answer.where(answerer_id: answerer.id, answerer_type:answerer.type, id_option: self.id)
answers.exists?
end
So I have 2 fields in my Articles table.
- :vote_up
- :vote_down
I have methods in my app of updating the :vote_up and :vote_down fields that work fine. What I want to do is order my articles by total votes (:vote_up minus :vote_down).
What is the best way to do this. Can I do this directly in the controller with a certain method? Or must I create a :vote_total field that updates automatically according to the values of the other two fields (if so how do you do this).
Many thanks!
Don't do this in your controller. This is meant to be done in your model. Controllers should just use the model.
You can do this in 2 ways:
Solution 1
Try this in your console (rails c)
Article
.unscoped
.select(%q(articles.*, (articles.vote_up - articles.vote_down) AS vote_total))
.order(%q(vote_total DESC))
and the implement it as a scope in your Article class
scope :order_by_total_votes, -> {
select(%q(articles.*, (articles.vote_up - articles.vote_down) AS vote_total))
.order(%q(vote_total DESC))
}
Solution 2
Create a field vote_total for your Article and update it every time one of the vote fields gets updated (use a before_save callback). Then you can do the same as in solution 1, but without the select part.
Suggestion
I would go with solution 2, because amongst others it is faster in queries
Hope this helps.
Thanks #Hiasinho for your direction. I ended up just creating a :vote_total to my Article database and updated it on both my upvote and downvote methods like so
#article.update_attributes(vote_total: #article.vote_total + 1)
Obviously it was a -1 for downvotes.
I'm writing an application that allows users to send one another messages about an 'offer'.
I thought I'd save myself some work and use the Mailboxer gem.
I'm following a test driven development approach with RSpec. I'm writing a test that should ensure that only one Conversation is allowed per offer. An offer belongs_to two different users (the user that made the offer, and the user that received the offer).
Here is my failing test:
describe "after a message is sent to the same user twice" do
before do
2.times { sending_user.message_user_regarding_offer! offer, receiving_user, random_string }
end
specify { sending_user.mailbox.conversations.count.should == 1 }
end
So before the test runs a user sending_user sends a message to the receiving_user twice. The message_user_regarding_offer! looks like this:
def message_user_regarding_offer! offer, receiver, body
conversation = offer.conversation
if conversation.nil?
self.send_message(receiver, body, offer.conversation_subject)
else
self.reply_to_conversation(conversation, body)
# I put a binding.pry here to examine in console
end
offer.create_activity key: PublicActivityKeys.message_received, owner: self, recipient: receiver
end
On the first iteration in the test (when the first message is sent) the conversation variable is nil therefore a message is sent and a conversation is created between the two users.
On the second iteration the conversation created in the first iteration is returned and the user replies to that conversation, but a new conversation isn't created.
This all works, but the test fails and I cannot understand why!
When I place a pry binding in the code in the location specified above I can examine what is going on... now riddle me this:
self.mailbox.conversations[0] returns a Conversation instance
self.mailbox.conversations[1] returns nil
self.mailbox.conversations clearly shows a collection containing ONE object.
self.mailbox.conversations.count returns 2?!
What is going on there? the count method is incorrect and my test is failing...
What am I missing? Or is this a bug?!
EDIT
offer.conversation looks like this:
def conversation
Conversation.where({subject: conversation_subject}).last
end
and offer.conversation_subject:
def conversation_subject
"offer-#{self.id}"
end
EDIT 2 - Showing the first and second iteration in pry
Also...
Conversation.all.count returns 1!
and:
Conversation.all == self.mailbox.conversations returns true
and
Conversation.all.count == self.mailbox.conversations.count returns false
How can that be if the arrays are equal? I don't know what's going on here, blown hours on this now. Think it's a bug?!
EDIT 3
From the source of the Mailboxer gem...
def conversations(options = {})
conv = Conversation.participant(#messageable)
if options[:mailbox_type].present?
case options[:mailbox_type]
when 'inbox'
conv = Conversation.inbox(#messageable)
when 'sentbox'
conv = Conversation.sentbox(#messageable)
when 'trash'
conv = Conversation.trash(#messageable)
when 'not_trash'
conv = Conversation.not_trash(#messageable)
end
end
if (options.has_key?(:read) && options[:read]==false) || (options.has_key?(:unread) && options[:unread]==true)
conv = conv.unread(#messageable)
end
conv
end
The reply_to_convesation code is available here -> http://rubydoc.info/gems/mailboxer/frames.
Just can't see what I'm doing wrong! Might rework my tests to get around this. Or ditch the gem and write my own.
see this Rails 3: Difference between Relation.count and Relation.all.count
In short Rails ignores the select columns (if more than one) when you apply count to the query. This is because
SQL's COUNT allows only one or less columns as parameters.
From Mailbox code
scope :participant, lambda {|participant|
select('DISTINCT conversations.*').
where('notifications.type'=> Message.name).
order("conversations.updated_at DESC").
joins(:receipts).merge(Receipt.recipient(participant))
}
self.mailbox.conversations.count ignores the select('DISTINCT conversations.*') and counts the join table with receipts, essentially counting number of receipts with duplicate conversations in it.
On the other hand, self.mailbox.conversations.all.count first gets the records applying the select, which gets unique conversations and then counts it.
self.mailbox.conversations.all == self.mailbox.conversations since both of them query the db with the select.
To solve your problem you can use sending_user.mailbox.conversations.all.count or sending_user.mailbox.conversations.group('conversations.id').length
I have tended to use the size method in my code. As per the ActiveRecord code, size will use a cached count if available and also returns the correct number when models have been created through relations and have not yet been saved.
# File activerecord/lib/active_record/relation.rb, line 228
def size
loaded? ? #records.length : count
end
There is a blog on this here.
In Ruby, #length and #size are synonyms and both do the same thing: they tell you how many elements are in an array or hash. Technically #length is the method and #size is an alias to it.
In ActiveRecord, there are several ways to find out how many records are in an association, and there are some subtle differences in how they work.
post.comments.count - Determine the number of elements with an SQL COUNT query. You can also specify conditions to count only a subset of the associated elements (e.g. :conditions => {:author_name => "josh"}). If you set up a counter cache on the association, #count will return that cached value instead of executing a new query.
post.comments.length - This always loads the contents of the association into memory, then returns the number of elements loaded. Note that this won't force an update if the association had been previously loaded and then new comments were created through another way (e.g. Comment.create(...) instead of post.comments.create(...)).
post.comments.size - This works as a combination of the two previous options. If the collection has already been loaded, it will return its length just like calling #length. If it hasn't been loaded yet, it's like calling #count.
It is also worth mentioning to be careful if you are not creating models through associations, as the related model will not necessarily have those instances in its association proxy/collection.
# do this
mailbox.conversations.build(attrs)
# or this
mailbox.conversations << Conversation.new(attrs)
# or this
mailbox.conversations.create(attrs)
# or this
mailbox.conversations.create!(attrs)
# NOT this
Conversation.new(mailbox_id: some_id, ....)
I don't know if this explains what's going on, but the ActiveRecord count method queries the database for the number of records stored. The length of the Relation could be different, as discussed in http://archive.railsforum.com/viewtopic.php?id=6255, although in that example, the number of records in the database was less than the number of items in the Rails data structure.
Try
self.mailbox.conversations.reload; self.mailbox.conversations.count
or perhaps
self.mailbox.reload; self.mailbox.conversations.count
or, if neither of those work, just try reloading as many of the objects as possible to see if you can get it to work (self, mailbox, conversations, etc.).
My guess is that something is messed up between memory and the DB. This is definitely a really weird error though, might wanna put in an issue on Rails to see why this would be the case.
The result of mailbox.conversations is cached after the first call. To reload it write mailbox.conversations(true)
How would I define in my controller to run and do the following when the Class is fetched in URL;
I need to find all "jobs" to current_user I'm guessing something like this;
#joblisting = current_user.Joblisting.find(params[:id])
Then I need to take those jobs and check if their column "job_status" has the text "completed" in them or other"
If the jobs_status is "completed" then I need to run code so I do an "if"
I would have to pass the calculation.
#joblisting = current_user.Joblisting.find(params[:id])
if #joblisting.where(:project_status => "completed")
number_to_currency(current_user.Joblisting.where(:project_status => 'completed').sum('jobprice') * 1.60 - current_user.Joblisting.where(:project_status => 'completed').sum('jobprice'))
Notifier.notify_payout(current_user).deliver
#joblisting.project_status = 'paid'
#joblisting.save
end
This is what I've got and I'm stuck with passing the calculation to the Notifier.notify_payout template.
I'm sure whomever knows rails better then me, will right away see my mistakes.
My answer will not give you the code you seek. I'm doing this because I feel like you still have a lot to learn, but I will tell you what to do, just not give you the code. If you say that this line of code works....
#joblisting = Joblisting.where(:developer_id => current_developer[:id])
if #joblisting.where(:project_status => "completed")
Notifier.notify_payout(current_developer).deliver
end
then so be it. As for updating the :project_status column from "completed" to "paid", there can be multiply ways to handle this. You could create a method inside your model (let's call it project_is_paid) that changes project status to paid and declare it inside notify_payout method on success.
But that might be confusing for someone else looking at your code and wondering why all of a sudden the record is changing from "completed" to "paid" inside the database. Plus you would have to pass the joblisting object as an argument which is even more work.
Another way to think of it is to just write a simple conditional statement inside the controller. If the mail is delivered, then call the method project_is_paid. Just be careful not to start adding all this logic to your controller, your controller should be concise and short. Let the model deal with the logic.
I want to conclude with going back to your working controller code you posted. I'm willing to bet that you can turn the two following lines into one.
#joblisting = Joblisting.where(:developer_id => current_developer[:id])
if #joblisting.where(:project_status => "completed")
Why do I say that? Well you are making two queries to the same table Job Listings. Here is a little help if you can't figure out how... link
And if I failed to answer your latest question in the comments, I'm sorry. Post an update in your question and I would be happy to update my own answer.
I periodically fetch the latest tweets with a certain hashtag and save them locally. In order to prevent saving duplicates, I use the method below. Unfortunately, it does not seem to be working... so what's wrong with this code:
def remove_duplicates
before = #tweets.size
#tweets.delete_if {|tweet| !((Tweet.all :conditions => { :twitter_id => tweet.twitter_id}).empty?) }
duplicates = before - #tweets.size
puts "#{duplicates} duplicates found"
end
Where #tweets is an array of Tweet objects fetched from twitter. I'd appreciate any solution that works and especially one that might be more elegant...
you can validate_uniqueness_of :twitter_id in the Tweet model (where this code should be). This will cause duplicates to fail to save.
Since it sounds like you're using the Twitter search API, a better solution is to use the since_id parameter. Keep track of the last twitter status id you got from your previous query and use that as the since_id parameter on your next query.
More information is available at Twitter Search API Method: search
array.uniq!
Removes duplicate elements from self. Returns nil if no changes are made (that is, no duplicates are found).
Ok, turns out the problem was a bit of different nature: When looking closer into it, I found out that multipe Tweets were saved with the twitter_id 2147483647... This is the upper limit for integer fields :)
Changing the field to bigint solved the problem. It took me very long to figure out since MySQL did silently fail and just reverted to the maximum value as long as it could. (until I added the unique index). I quickly tried it out with postgres, which returned a nice "Integer out of range" error, which then pointed me to the real cause of the problem here.
Thanks Ben for the validation and indexing tips, as they lead to much cleaner code now!