Difference between array.count and array.size

Question

Is there any difference between array.count and array.size?

I am getting errors sometimes on production environment while using array.count, but the same works fine when I use array.size.

There was a good post about this a few years back: blog.hasmanythrough.com/2008/2/27/count-length-size — William
– William, Commented Dec 9, 2010 at 16:51

Simone Carletti · Accepted Answer · 2010-12-09 09:11:39Z

28

Starting from Ruby 1.8.7, Array#count is the same of Array#size.

Please note that Array#count doesn't exist in Ruby versions lower than 1.8.7 so if you are running Ruby 1.8.6 in production, it will raise a NoMethodError.

Also, make sure you are talking about arrays. In ActiveRecord, for example, #size and #count are slightly different. #size understands caching like counter cache, while count doesn't.

answered Dec 9, 2010 at 9:11

Simone Carletti

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1 Comment

ssri Over a year ago

Thanks for that. Now only i realized my development system has ruby 1.8.7 and staging had 1.8.6.

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