CODEWITHSUNDEEP
ruby-on-rails
user1175969
user1175969

Reputation: 570

Generate unique sequential id

How do I generate a unique sequential ID (that follows a pattern), each time a record is created? How do I address concurrency issues?

I want this ID to follow a fixed pattern. e.g.: ABC00001, ABC00002, ABC00003, etc

I am doing this to generate student IDs, and I want student IDs within an institute to to be sequential. There will be multiple institutes using my tool.

Upvotes: 2

Views: 1939

Answers (1)

omnikron
omnikron

Reputation: 2321

If you're using active record then a unique sequential id (id) is already created by default and takes care of all concurrency issues for you. If you need to use it for queries then a separate column might be the way forward, but if you just need to display it in a certain format you could simply define a method on your model like:

class MyModel
  def my_unique_id
    "ABC%.5d" % id
  end
end

test = MyModel.create
test.id #=> 1
test.my_unique_id #=> "ABC00001"

test2 = MyModel.create
test2.id #=> 2
test2.my_unique_id #=> "ABC00002"

EDIT

Ah, you didn't mention that you needed the identifiers to be sequential within an Institute. Are you using PostgreSQL? If so the sequenced gem might be a good bet – it adds an acts_as_sequence method which allows you to do this:

class Student
  acts_as_sequenced scope: :institute_id, column: :sequential_id
  #...
end

If you are not using PostgreSQL you'd need to find a way of dealing with concurrency locks in your database system of choice, as the gem only caters for postgres (see here for how).

Upvotes: 6

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