Ruby-on-rails array.count 和 array.size 的区别
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Difference between array.count and array.size
提问by ssri
Is there any difference between array.countand array.size?
有什么区别array.count和array.size？
I am getting errors sometimes on production environment while using array.count, but the same works fine when I use array.size.
我在生产环境中有时会收到错误，同时使用array.count，但同样的作品很好，当我使用array.size。
回答by Simone Carletti
Starting from Ruby 1.8.7, Array#countis the same of Array#size.
从 Ruby 1.8.7 开始，Array#count与Array#size.
Please note that Array#countdoesn'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.
请注意，Array#count在低于 1.8.7 的 Ruby 版本中不存在，因此如果您在生产中运行 Ruby 1.8.6，它将引发NoMethodError.
Also, make sure you are talking about arrays. In ActiveRecord, for example, #sizeand #countare slightly different. #sizeunderstands caching like counter cache, while count doesn't.
另外，请确保您在谈论数组。例如，在 ActiveRecord 中，#size和#count略有不同。#size像计数器缓存一样理解缓存，而 count 不理解。
