Question

i want to add the “available time” when the user establish a vote . how to implement?

For example i set up a vote ,and it is available to vote by 2012.1.1.In addition ,the vote’s “available time” range from one day to one year.

Answer 1

add a date column like “expires_at” and then you run a custom validation like:

Solution A*

if you have one single table called votings:

id | name | votes | expires_at

expires_at is a Date column

Now your model looks like (voting.rb):

class Voting < ActiveRecord::Base
  validate :check_expiry_date, :on => :update

  def check_expiry_date
    self.errors.add('base', 'Voting is closed') if self.expired?
  end

  def expired?
    self.expires_at < Date.today
  end
end

Now in your controller:

@voting = Voting.find(someid)
@voting.votes += 1

if @voting.save
  # everyhing ok
else
  # maybe the voting is closed, check validation messages
end

Solution B

If you have a 2-Table approach like:

Table Votings:

id | name | expires_at

Table Votes:

id | user_id | voting_id

You need two models:

voting.rb

class Voting < ActiveRecord::Base
  has_many :votes

  def expired?
    self.expires_at < Date.today
  end   
end

votes.rb

class Vote < ActiveRecord::Base
  belongs_to :voting
  belongs_to :user

  # only one vote per user per voting
  validates_uniqueness_of :user_id, :scope => :voting_id

  # check expiry date
  validate :check_expiry_date, :on => :create

  def check_expiry_date
    self.errors.add('base', 'Voting is closed') if self.voting.expired?
  end
end

Your Controller:

@vote = Vote.new
@vote.user_id   = some_user_id
@vote.voting_id = some_voting_id

if @vote.save
  # everything ok
else 
  # maybe the voting is closed
end

---

Creating a new Voting:

@voting             = Voting.new
@voting.name        = 'President Election 2011'
@voting.expires_at  = 1.year.from_now
@voting.save