CODEWITHSUNDEEP
ruby-on-railsrubyruby-on-rails-4
Petros Kyriakou
Petros Kyriakou

Reputation: 5343

Record not always found

Consider the following

# setup an array of the question ids so far
questions_array = []
questions_array.push(session[:questions_array])

# take a random question whom id is not included in the session[:questions_array]
@question = Question.offset(rand(Question.count)).where('id NOT IN (?)',questions_array).take

# push id to array and later on assign the new array to the session
questions_array.push(@question.id)
session[:questions_array] = questions_array

I have two questions database. One of the two gets returned the other one gives me the error

NoMethodError (undefined method 'id' for nil:NilClass):

this line gives the error questions_array.push(@question.id)

this does not happen everytime! and that is what's strange!

Upvotes: 0

Views: 36

Answers (2)

Arup Rakshit
Arup Rakshit

Reputation: 118289

This is how, you can solve it though:

Question
  .where.not(id: questions_array)
  .order('random()')
  .first

But if the questions table get say more than 10,000 records for example, it will be slow. Then you could write recursive procedure, which will pick a random record and check some condition. if condition matches, returns the record, or recursion will go on with some base condition to break in worst case.

Upvotes: 2

Petros Kyriakou
Petros Kyriakou

Reputation: 5343

My bad seems that the problem lies in the fact that i first get a random id and then check if that id is not in the array which is not what i wanted. So if the random id was included in the array it would give an error as there is none to take.

this is the new line of code.

@question = Question.where('id NOT IN (?)',questions_array).first

Upvotes: 0

Related Questions