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Using Date Objects With Ruby Ranges

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I used to have some really ugly code to generate the archive links you see on the right column of this blog. It was terrible. Granted it was some of the first code I wrote on this blog, and I was cruising through it because I just wanted to get it done and working, but still, it's not really a valid excuse. It can be seen here.

I had a thought the other day that it would be much better handled by the Range class, and boy was I right, although it involved a tweak.

The Range class allows to request values from some value to another value (inclusive or exclusive) using this syntax:

1..10

See the little dots in the middle? That would return me a Range with the numbers 1 up to 10 (inclusive). If I use 3 dots like this:

1...10

I would get 1 up to 9, or 1 to 10 exclusive.

Inclusive and exclusive in this case refer to the last value in the Range.

How does Range get the values to put in there? The #succ method!

The successor is the thing that follows something, so the successor of 1 is 2 (in the Integer space anyway), and Range uses this to generate the list of items.

You can leverage this too, since #succ is just another method.

I created an ArchiveDate class which inherits from Date and defined #succ to be:

self + 1.month

I require active_support for the #month method. So now, if I do something like this:

ArchiveDate.new(2009,4,1)..ArchiveDate.new(2010,1,1)

I'll get a list of ArchiveDate objects, which are by extension Date objects, each one representing the first of the month. So I get April, May, June, etc. Then I can loop through them and print out the required archive links in my sidebar. Much better than the old code!

The commit where I changed this over is here so feel free to check it out, and make fun of it, or suggest even better ways to do it.


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