将日期与 Rails3 中的 Datetime Created_at 进行比较

Question

So I'm trying to do things like so:

today = Date.today - 1
todaysReport = Report.where(:created_at => today).find_by_user_id(user.id)

The problem is created_at is a datetime, so it won't find any matches..Any suggestions?

Answer 1

You probably want something like this:

yesterday = Time.now - 1.day
user = User.find(user_id)

todaysReport = user.reports.where(["created_at >= ? AND created_at <= ?", yesterday.beginning_of_day, yesterday.end_of_day])

Answer 2

In postgres, you can cast a timestamp as a date. For example:

Report.where("created_at::date =?", Date.today - 1)

Extract date (yyyy/mm/dd) from a timestamp in PostgreSQL

Answer 3

You need to compare against a range from one midnight to the next. Also, this is a good candidate for making your own class method for higher flexibility.

class Report
  # All reports created on the specified Date
  def self.created_on(date)
    where(['created_at >= ? AND created_at < ?', date, date + 1])
  end
end

# Find all reports created yesterday by our user
Report.created_on(Date.today - 1).where(:user_id => user.id)

Answer 4

In Rails 5.1 and greater, you can use all_day instance method like this:

today = Date.today - 1
todaysReport = Report.where(created_at: today.all_day).find_by_user_id(user.id)

Answer 5

It can also be TimeWithZone if time zone specified in application config. To get Date to TimeWithZone you have to do like Date.today.to_time.in_time_zone.

Answer 6

Have you tried using #to_datetime , which Rails adds to the Date and Time classes?

Report.where(:created_at => today.to_datetime).find_by_user_id(user.id)

Actually surprised AR doesn't handle this for you.