Question

I want to create a subclass of Time, let’s say MyTime, so that I can define (especially formatting-related) methods without polluting the Time class.

class MyTime < Time; end

For some constructor methods defined on Time, I can use them in MyTime like this:

MyTime.now

but sometimes I need to create an instance of MyTime based on an instance of Time. For example, I would like to have an instance of MyTime based on:

File.mtime(path_to_some_file)

which is a Time instance. The constructor Time#new does not accept Time instances, so I cannot use that. How can I do it?

Answer 1

The Time class has an at class method that takes a Time instance as an argument:

at(time) → time
[…]

Creates a new time object with the value given by time, […]

So you can say things like this:

>> class MyTime < Time; end
>> mt = MyTime.at(File.mtime(path_to_some_file))
>> mt.class
=> MyTime

So converting a Time to a MyTime is a simple matter of calling MyTime.at.