Question

I have a Rails 3 application with a prescription model. The model has a number of fields, two of them are to calculate and display the duration of a prescription.

At the moment the user enters a value in a text field such as ‘3 Months’ and then manually changes a datetime input to three months from now. This seems like a perfect form to automate for the user.

Currently the fields are like this:

Duration of Treatment

<%= f.text_field :duration, :class => "input-text" %>

Date of Expiry

<%= f.datetime_select :expiry, :order => [:day, :month, :year], :class => "input-text" %>

So, my question. How can I create two dropdown lists for the duration field such as:

[1] [Day]

The user can select the number from the first list and in the second they can choose Day, Week or Month.

The value they pick using the duration select boxes would be saved as a text string e.g. “1 month” and the value of the Time.now in 1 month would be saved as a datetime value in the expiry column.

Is something like this possible to do? If so, how?

Answer 1

I’ll provide an example of how you’d use the chronic gem, since it seems tailor-made for this purpose:

require 'chronic'
duration = "3 months" # => "3 months" 
Time.now # => 2012-07-09 18:43:50 -0700 
Chronic.parse(duration + " from now") # => 2012-10-09 18:43:55 -0700 

If I understand your use case correctly, you can then just get rid of the datetime select entirely. Ask the user for the text duration and assign that to the text attribute. Then use chronic to determine the time value from the text parameter and assign that to the datetime attribute. For extra credit get the parsed time value asynchronously and display it on the page before they submit the form so they can see that what they are submitting makes sense.