问题描述
有一个简单的方法来获取集合中属性的平均值吗？
Is there an easy way to obtain the average of an attribute in a collection?
例如，每个用户都有一个分数。
For instance, each user has a score.
给定一个用户集合（@users），如何获得该组的平均分数？
Given a collection of user(s) (@users), how can you get the average score for the group?
有什么像@ users.average（：score）？我想我为数据库字段遇到类似这样的东西，但我需要它为一个集合工作
Is there anything like @users.average(:score)? I think I came across something like this for database fields, but I need it to work for a collection...
推荐答案
你的问题，实际上可以做：
For your question, one could actually do:
@users.collect(&:score).sum.to_f/@users.length if @users.length > 0
早些时候我想，@ users.collect（&：score）。对于数据库字段，User.average（：score）将工作。您还可以添加：条件，如其他activerecord查询。
Earlier I thought, @users.collect(&:score).average would have worked. For database fields, User.average(:score) will work. You can also add :conditions like other activerecord queries.
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