How do you subtract from a datetime?

Question

I'd like to write a simple function to say in hours:

How much time has passed since this has been created?

My attempts:

-time = DateTime.now.hour - (self.created_at.hour)

Does anyone know how to do this in Ruby on Rails?

Answer 1

Rails usually uses Time, not DateTime. Why don't you do Time.now - self.created_at? Then you can convert from seconds to hours by dividing by 3600.

Answer 2

Got it!. First you have to make sure your data is in the same data it will be subtracted from whether its a Time or a DateTime. I chose time. Then you divide it by Ruby's built in time methods. This translates into how many days, but it can also be, 1.hour. etc.

(Time.now - self.created_at.to_time)/1.day