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Formatting Dates: the Rails way

4th May 2018

Working with dates in Rails can become a problem after a while, especially when in your project you have code like this:

t = Time.now
t.strftime("Printed on %m/%d/%Y")

At first glance, this might look good because this is a very simple date being formatted. But what happens when there are a lot of dates in many places and all of them with the same format? You end with a lot of strftime calls with the same arguments spread all over your project.

You might be thinking the solution would be to wrap the formatting in a helper method like:

def formatted_date(date)
    date.strftime("Printed on %m/%d/%Y")

It does work, but there is a better way of doing it in Rails.

Managing custom date formats with Active Support

ActiveSupport is a Rails library that provides a lot of utility methods, one of those methods is the to_formatted_s, here’s how it works:

t = Time.now 
t.to_formatted_s(:iso8601) #=> "2018-05-03T16:17:33-05:00"

In order to add your own date formats you can create the following initializer file:

# config/initializers/date_formats.rb
Time::DATE_FORMATS[:flip_year] = '(╯°□°)╯︵%Y'

And now you can use your custom date formats everywhere like this:

t = Time.now 

puts t.to_formatted_s(:flip_year) # => (╯°□°)╯︵2018

# or alias:
puts t.to_s(:flip_year) # => (╯°□°)╯︵2018

As you can see, this is a more organized way to keep all your date formats in a single place. The initializer file can work as a reference for other developers to figure out if there’s a format they can use and avoid code duplication.

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