Ruby Cookbook

Recipe 3.1. Finding Today's Date Problem You need to create an object that represents the current date and time, or a time in the future or past. Solution The factory method Time.now creates a Time object containing the current lo...

Recipe 3.2. Parsing Dates, Precisely or Fuzzily Problem You want to transform a string describing a date or date/time into a Date object. You might not know the format of the string ahead of time. Solution The best solution is to pas...

Recipe 3.3. Printing a Date Problem You want to print a date object as a string. Solution If you just want to look at a date, you can call Time#to_s or Date#to_s and not bother with fancy formatting: require 'date' Time.now.to_s ...

Recipe 3.4. Iterating Over Dates Problem Given a point in time, you want to get somewhere else. Solution All of Ruby's time objects can be used in ranges as though they were numbers. Date and DateTime objects iterate in increme...

Recipe 3.5. Doing Date Arithmetic Problem You want to find how much time has elapsed between two dates, or add a number to a date to get an earlier or later date. Solution Adding or subtracting a Time object and a number adds...

Recipe 3.6. Counting the Days Since an Arbitrary Date Problem You want to see how many days have elapsed since a particular date, or how many remain until a date in the future. Solution Subtract the earlier date from the later one. If you...

Recipe 3.7. Converting Between Time Zones Problem You want to change a time object so that it represents the same moment of time in some other time zone. Solution The most common time zone conversions are the conversion of syste...

Recipe 3.8. Checking Whether Daylight Saving Time Is in Effect Problem You want to see whether the current time in your locale is normal time or Daylight Saving/Summer Time. Solution Create a Time object and check its isdst method...

Recipe 3.9. Converting Between Time and DateTime Objects Problem You're working with both DateTime and Time objects, created from Ruby's two standard date/time libraries. You can't mix these objects in comparisons, iterations, or date arit...

Recipe 3.10. Finding the Day of the Week Problem You want to find the day of the week for a certain date. Solution Use the wday method (supported by both Time and DateTime) to find the day of the week as a number between 0 and 6. ...

Recipe 3.11. Handling Commercial Dates Problem When writing a business or financial application, you need to deal with commercial dates instead of civil or calendar dates. Solution DateTime offers some methods for working with commer...

Recipe 3.12. Running a Code Block Periodically Problem You want to run some Ruby code (such as a call to a shell command) repeatedly at a certain interval. Solution Create a method that runs a code block, then sleeps until it's time ...

Recipe 3.13. Waiting a Certain Amount of Time Problem You want to pause your program, or a single thread of it, for a specific amount of time. Solution The Kernel#sleep method takes a floating-point number and puts the current thread t...