如何获得此数组中的唯一元素? [英] How do I get unique elements in this array?

问题描述

使用 Mongoid.不幸的是，Mongoid 不允许选择独特的/独特的！得到了这些结果.如您所见，有 7 个结果.如果仔细看(在 user_id 处)，只有 2 个用户.

<预><代码>[#<Activity _id: 4cea6c4572357e00fa00011a, created_at: 2010-11-22 13:12:37 UTC, updated_at: 2010-11-22 13:12:37 UTC, action: "Attend":4cea2fb872357e00fa000025')，artist_id: nil, media_id: BSON::ObjectId('4cea447472357e00fa00009a')>,#<Activity _id: 4cea6c3072357e00fa000116, created_at: 2010-11-22 13:12:16 UTC, updated_at: 2010-11-22 13:12:16 UTC, action: "Attend: B'SONId", user_Id4cea2fb872357e00fa000025')，artist_id: nil, media_id: BSON::ObjectId('4cea447472357e00fa00009a')>,#<Activity _id: 4cea6bdd72357e00fa00010d, created_at: 2010-11-22 13:10:53 UTC, updated_at: 2010-11-22 13:10:53 UTC, action: "Attend", user_id(4cea2fb872357e00fa000025')，artist_id: nil, media_id: BSON::ObjectId('4cea447472357e00fa00009a')>,#<Activity _id: 4cea46df72357e00fa0000a4, created_at: 2010-11-22 10:33:03 UTC, updated_at: 2010-11-22 10:33:03 UTC, action: "Attend", user_id(4cea2fb872357e00fa000025')，artist_id: nil, media_id: BSON::ObjectId('4cea447472357e00fa00009a')>,#<Activity _id: 4cea40c572357e00fa00006f, created_at: 2010-11-22 10:07:01 UTC, updated_at: 2010-11-22 10:07:01 UTC, action: "Attend(Battend", user_ObjectId)4cea2fb872357e00fa000025')，artist_id: nil, media_id: BSON::ObjectId('4cea3c8b72357e00fa00005e')>,#<Activity _id: 4cea3ca172357e00fa000062, created_at: 2010-11-22 09:49:21 UTC, updated_at: 2010-11-22 09:49:21 UTC, action: "Attend", user_id(4cea39b772357e00fa000046')，artist_id:nil，media_id:BSON::ObjectId('4cea3c8b72357e00fa00005e')>，#<Activity _id: 4cea344a72357e00fa00003f, created_at: 2010-11-22 09:13:46 UTC, updated_at: 2010-11-22 09:13:46 UTC, action: "Attend:B'SONId", user_id4cea2fb872357e00fa000025')，artist_id:nil，media_id:BSON::ObjectId('4cea306c72357e00fa000031')>]

我正在查看 this，我想我可以做一些类似的事情，这样我的数组现在看起来像这样:

<预><代码>[#<Activity _id: 4cea6c4572357e00fa00011a, created_at: 2010-11-22 13:12:37 UTC, updated_at: 2010-11-22 13:12:37 UTC, action: "Attend":4cea2fb872357e00fa000025')，artist_id: nil, media_id: BSON::ObjectId('4cea447472357e00fa00009a')>,#<Activity _id: 4cea3ca172357e00fa000062, created_at: 2010-11-22 09:49:21 UTC, updated_at: 2010-11-22 09:49:21 UTC, action: "Attend", user_id(4cea39b772357e00fa000046')，artist_id:nil，media_id:BSON::ObjectId('4cea3c8b72357e00fa00005e')>]

我不关心提取的是哪种结果组合.只要我在结果集中有唯一的 user_id.有人知道如何实现吗?

解决方案

你可以只使用 uniq 方法.假设你的数组是 ary，调用:

ary.uniq{|x|x.user_id}

这将返回一个具有唯一 user_ids 的集合.

Using Mongoid. Unfortunately, Mongoid does not allow for selecting unique / distinct! Have gotten these results. As you can see, there are 7 results. If you look carefully (at user_id), there are only 2 users.

[
  #<Activity _id: 4cea6c4572357e00fa00011a, created_at: 2010-11-22 13:12:37 UTC, updated_at: 2010-11-22 13:12:37 UTC, action: "Attend", user_id: BSON::ObjectId('4cea2fb872357e00fa000025'), artist_id: nil, media_id: BSON::ObjectId('4cea447472357e00fa00009a')>, 
  #<Activity _id: 4cea6c3072357e00fa000116, created_at: 2010-11-22 13:12:16 UTC, updated_at: 2010-11-22 13:12:16 UTC, action: "Attend", user_id: BSON::ObjectId('4cea2fb872357e00fa000025'), artist_id: nil, media_id: BSON::ObjectId('4cea447472357e00fa00009a')>, 
  #<Activity _id: 4cea6bdd72357e00fa00010d, created_at: 2010-11-22 13:10:53 UTC, updated_at: 2010-11-22 13:10:53 UTC, action: "Attend", user_id: BSON::ObjectId('4cea2fb872357e00fa000025'), artist_id: nil, media_id: BSON::ObjectId('4cea447472357e00fa00009a')>, 
  #<Activity _id: 4cea46df72357e00fa0000a4, created_at: 2010-11-22 10:33:03 UTC, updated_at: 2010-11-22 10:33:03 UTC, action: "Attend", user_id: BSON::ObjectId('4cea2fb872357e00fa000025'), artist_id: nil, media_id: BSON::ObjectId('4cea447472357e00fa00009a')>, 
  #<Activity _id: 4cea40c572357e00fa00006f, created_at: 2010-11-22 10:07:01 UTC, updated_at: 2010-11-22 10:07:01 UTC, action: "Attend", user_id: BSON::ObjectId('4cea2fb872357e00fa000025'), artist_id: nil, media_id: BSON::ObjectId('4cea3c8b72357e00fa00005e')>, 
  #<Activity _id: 4cea3ca172357e00fa000062, created_at: 2010-11-22 09:49:21 UTC, updated_at: 2010-11-22 09:49:21 UTC, action: "Attend", user_id: BSON::ObjectId('4cea39b772357e00fa000046'), artist_id: nil, media_id: BSON::ObjectId('4cea3c8b72357e00fa00005e')>, 
  #<Activity _id: 4cea344a72357e00fa00003f, created_at: 2010-11-22 09:13:46 UTC, updated_at: 2010-11-22 09:13:46 UTC, action: "Attend", user_id: BSON::ObjectId('4cea2fb872357e00fa000025'), artist_id: nil, media_id: BSON::ObjectId('4cea306c72357e00fa000031')>
] 

I was looking at this, and was thinking I could do something similar so that my array would now look like this:

[
  #<Activity _id: 4cea6c4572357e00fa00011a, created_at: 2010-11-22 13:12:37 UTC, updated_at: 2010-11-22 13:12:37 UTC, action: "Attend", user_id: BSON::ObjectId('4cea2fb872357e00fa000025'), artist_id: nil, media_id: BSON::ObjectId('4cea447472357e00fa00009a')>, 
  #<Activity _id: 4cea3ca172357e00fa000062, created_at: 2010-11-22 09:49:21 UTC, updated_at: 2010-11-22 09:49:21 UTC, action: "Attend", user_id: BSON::ObjectId('4cea39b772357e00fa000046'), artist_id: nil, media_id: BSON::ObjectId('4cea3c8b72357e00fa00005e')>
]

I'm not concerned which combination of results are extracted. As long as I have unique user_id's in the result set. Anyone know how this can be achieved?

解决方案

You can just use the method uniq. Assuming your array is ary, call:

ary.uniq{|x| x.user_id}

and this will return a set with unique user_ids.

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