在Rails的4 has_​​and_belongs_to_many关系使用的uniq [英] Using uniq in a has_and_belongs_to_many relationship in Rails 4

问题描述

我想实现像这样一个 has_​​and_belongs_to_many 关系的唯一约束：

 类用户
  has_and_belongs_to_many：FOOS，uniq的：真正的
结束
 

由于我只希望唯一的 FOOS 当我打电话 user.foos ，我加了 uniq的选项。由于升级到Rails 4，我开始得到以下警告：

  

DE preCATION警告：在下列选项您   User.has_and_belongs_to_many：FOOS声明是代precated：uniq的。   请使用范围块来代替。例如，以下内容：

 的has_many：spam_comments，条件：{垃圾邮件：真}，将class_name：注释
 

     

应该被改写为：

 的has_many：spam_comments， - ＆GT; {其中，垃圾邮件：真}，将class_name：注释
 

我已经尝试了许多不同的组合，并通过源读取，但无法弄清楚如何写的唯一约束删除警告？

解决方案

 类用户
  has_and_belongs_to_many：FOOS， - ＆GT; {}的uniq
结束
 

根据<一href="http://edgeguides.rubyonrails.org/association_basics.html#scopes-for-has-and-belongs-to-many">documentation这里

I'm trying to implement a unique constraint on a has_and_belongs_to_many relationship like so:

class User
  has_and_belongs_to_many :foos, uniq: true
end

Because I only want unique foos when I call user.foos, I added the uniq option. Since upgrading to Rails 4 I've started to get the following warning:

DEPRECATION WARNING: The following options in your User.has_and_belongs_to_many :foos declaration are deprecated: :uniq. Please use a scope block instead. For example, the following:

  has_many :spam_comments, conditions: { spam: true }, class_name: 'Comment'

should be rewritten as the following:

  has_many :spam_comments, -> { where spam: true }, class_name: 'Comment'

I've tried a number of different combinations, and read through the source, but can't figure out how to write the unique constraint to remove the warning?

解决方案

class User
  has_and_belongs_to_many :foos, -> { uniq }
end

According to the documentation here

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