检查一个时间范围是否在另一个时间范围和Ruby on Rails多少小时之间

Question

So I have a start_time and end_time. Which is maximum 24 hours. I guess I firstly need to check if this timerange is within another timerange say 21:00-01:00. If it is I need to know how many of the hours is within the timerange. Any ideas?

Answer 1

Use ((two- one) / 3600).round

for example

one=Time.now #=>2019-01-23 21:19:19 +0530
two=Time.now + 1*60*60 #=>2019-01-23 22:19:27 +0530
((two- one) / 3600).round #=>1 

difference is 1 hour for two different Time instance.

Answer 2

I assume the four arguments of the method below are strings of the form "HH:MM" or "HH:MM:SS". I have provided a pure-Ruby solution that makes string comparisons only (for example: "17:26" < "18:00" #=> true ). That is, I do not convert the strings to Time objects.

def time_within_ref?(time_start, time_end, ref_start, ref_end)
  (time_start >= ref_start) &&
  (adj_hour(time_start, time_end) <= adj_hour(ref_start, ref_end))
end

def adj_hour(start_str, end_str)
  end_str[0,2] = (end_str[0,2].to_i + 24).to_s if end_str < start_str
  end_str
end

Here are a few examples.

time_within_ref?("19:00", "02:00", "18:00", "03:00")
  #=> true 
time_within_ref?("19:00", "04:00", "18:00", "03:00")
  #=> false
time_within_ref?("17:00", "02:00", "18:00", "03:00")
  #=> false
time_within_ref?("18:00", "02:00", "18:00", "03:00")
  #=> true

Answer 3

What do you mean by "within"? Do you mean that you want to test if there's any overlap between the ranges, or if the first range is fully contained within another?

You can use Time objects in ranges and exploit #cover? to check for overlap

start_time = 5.hours.ago
end_time = 4.hours.ago

check_range_start = (4.5).hours.ago
check_range_end = (3.5).hours.ago
check_range = (check_range_start..check_range_end)

check_range.cover?(end_time)   # => true
check_range.cover?(start_time) # =>false

If both ends of the range is covered by your check range, then your range is fully covered. If only one end is covered, then you have overlap. If neither end is covered, then the ranges do not intersect.

Once you know if there's intersection, then you can trivially compute the distance from one end of the time range to one end of your check range; if you want to know how much time between your check range start and your input start time, simply subtract start_time - check_range_start .

Answer 4

There are several ways to perform this in the database which are far more performant than loading a bunch of records into Rails.

While "pure ruby" solutions are a quick fix they will exhaust the available memory and crash your server given a non-trivial amount of records.

You can use a range together with .where to create a WHERE start_time BETWEEN a AND b clause that ensures that a time is within A and B.

starts_today = Model.where(
  start_time: Time.current.beginning_of_day..Time.current.end_of_day
)

If you want to ensure that the entire span between start_time and end_time is within a set of bounds you can write you own where clause:

Model.where(
  "start_time > :a AND end_time < :b", 
  a: Time.current.beginning_of_day, 
  b: Time.current.end_of_day
)

I need to know how many of the hours is within the timerange.

You can do this with the time/date functions in your database. On postgres for example you can do:

bounds = Time.current.beginning_of_day..Time.current.end_of_day
Model.select(
  "models.*,  (EXTRACT(HOUR FROM end_time - start_time ) - EXTRACT(HOUR FROM end_time - '#{ bounds.end.iso8601 }')) AS number_of_hours"
)

Again calculating this in the DB is vital if you for example want to use this in a WHERE clause.

Answer 5

I think I figured it out. Shift.start_time.strftime("%H:%M") => '20:00' && Shift.end_time.strftime("%H:%M") <= '01:00' The .to_time was messing with me and also the ordering.