CODEWITHSUNDEEP
ruby-on-railsruby
Pedro Souza
Pedro Souza

Reputation: 337

Using Callback Rails with parameter - Ruby

EDITED:

I trying to refactore this:

self.before_create do |obj|
  obj.position = self.class.count
end

to this: 

self.before_create :set_position

private

def set_position
  obj.position = self.class.count
end

But, Its displaying Error: 

 undefined local variable or method `obj'

How fix this?

Upvotes: 0

Views: 88

Answers (2)

captainpete
captainpete

Reputation: 6222

class Something < ActiveRecord::Base
  before_create :set_position

  protected
  def set_position
    self.position = self.class.count
  end
end

Be aware that if you use class variables you might run into trouble if your server uses multiple processes (@@count getting out of sync between them). A functional style queries count from the db.

Note: A lot of this behavior (including properly implemented atomic changes to lists) can be found in the acts_as_list gem, that used to be part of Rails a while back. I suggest using that.

Upvotes: 1

megas
megas

Reputation: 21791

class YourClass < AR

  before_create :set_position

  private

  def set_position
    self.position = @@count
  end
end

The set_position method is instance method, so self is assigned to the instance. The count I believe should be a class variable.

Upvotes: 2

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