CODEWITHSUNDEEP
mysqlruby-on-railsruby
7elephant
7elephant

Reputation: 2929

Rails: auto increment column with scope

I have projects and issues. The issue number (not ID) must be auto-increment but scoped with project_id. Any gem or easy way to accomplish that? Thank you!

Edit: acts_as_list will do the job, but what if a record is deleted? The next issue will be with it's number.

Upvotes: 6

Views: 2832

Answers (2)

graywh
graywh

Reputation: 9840

You could use the counter_cache on the Project issues association and override Project's decrement_counter to do nothing.

Upvotes: 0

elijah
elijah

Reputation: 2924

in your Issue class:

belongs_to :project
before_validation( :on => :create ) do 
  self.issue_number = self.project.issues.collect { | issue | issue.issue_number }.max + 1
end

(or thereabouts) -- essentially, before the new object is created, find the max issue number of the issues associated with the issue's project, increment that, and use it for the new issue number...

Upvotes: 3

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