Check for Dates Overlap in Ruby on Rails

Question

I have a model that has two columns (started_at and ended_at). I want to add a custom validator that ensures that no other record exists with dates that overlap with the record I'm validating. So far I have:

# app/models/event.rb

class Event < ActiveRecord::Base
  validates_with EventValidator
end

# app/validators/event_validator.rb

class EventValidator < ActiveModel::Validator
  attr_reader :record

  def validate(record)
    @record = record

    validate_dates
  end

  private

  def validate_dates
    started_at = record.started_at
    ended_at   = record.ended_at
    arel_table = record.class.arel_table

    # This is where I'm not quite sure what type of query I need to perform...
    constraints = arel_table[:started_at].gteq(ended_at)
      .and(arel_table[:ended_at].lteq(started_at))

    if record.persisted?
      constraints = constraints
        .and(arel_table[:id].not_eq(record.id))
    end

    if record.class.where(constraints).exists?
      record.error[:base] << "Overlaps with another event"
    end
  end 
end

I don't know exactly what query I need to ensurethat there is no overlapping. Any help is greatly appreciated

Plamena Gancheva · Accepted Answer · 2016-02-12 07:25:07Z

1

I don't use Arel but I think the query should be:

 constraints = arel_table[:started_at].lteq(ended_at)
      .and(arel_table[:ended_at].gteq(started_at))

Two periods overlap when

period1.start < period2.end
period1.end > period2.start

edited Feb 12, 2016 at 7:25

answered Feb 11, 2016 at 14:54

Plamena Gancheva

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Comments

mikdiet · Accepted Answer · 2016-02-11 14:53:29Z

0

Have a look at Validates Overlap gem

You can either use it instead your code or take condition code from it

  # Return the condition string depend on exclude_edges option.
  def condition_string(starts_at_attr, ends_at_attr)
    except_option = Array(options[:exclude_edges]).map(&:to_s)
    starts_at_sign = except_option.include?(starts_at_attr.to_s.split(".").last) ? "<" : "<="
    ends_at_sign = except_option.include?(ends_at_attr.to_s.split(".").last) ? ">" : ">="
    query = []
    query << "(#{ends_at_attr} IS NULL OR #{ends_at_attr} #{ends_at_sign} :starts_at_value)"
    query << "(#{starts_at_attr} IS NULL OR #{starts_at_attr} #{starts_at_sign} :ends_at_value)"
    query.join(" AND ")
  end

answered Feb 11, 2016 at 14:53

mikdiet

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Comments

ConnorCMcKee · Accepted Answer · 2016-02-11 14:56:11Z

0

I would construct a query that looks something like this:

Event.exists?( 'started_at < ? AND ended_at > ?', ended_at, started_at )

If this returns true, an overlapping record exists.

answered Feb 11, 2016 at 14:56

ConnorCMcKee

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