ActiveRecord_fancy_pluck.md

2.2.3 :006 > a.each do |x|
2.2.3 :007 >     puts x.body
2.2.3 :008?>   end
comment123
+----+------------+------------------------+-------------------------+---------+
| id | body       | created_at             | updated_at              | post_id |
+----+------------+------------------------+-------------------------+---------+
| 1  | comment123 | 2016-02-04 07:00:34... | 2016-02-04 07:47:09 UTC | 221     |
+----+------------+------------------------+-------------------------+---------+
1 row in set
2.2.3 :009 > a.all
  Comment Load (0.5ms)  SELECT "comments".* FROM "comments" WHERE (post_id = 221)
+----+------------+------------------------+-------------------------+---------+
| id | body       | created_at             | updated_at              | post_id |
+----+------------+------------------------+-------------------------+---------+
| 1  | comment123 | 2016-02-04 07:00:34... | 2016-02-04 07:47:09 UTC | 221     |
+----+------------+------------------------+-------------------------+---------+
1 row in set
2.2.3 :010 > a
+----+------------+------------------------+-------------------------+---------+
| id | body       | created_at             | updated_at              | post_id |
+----+------------+------------------------+-------------------------+---------+
| 1  | comment123 | 2016-02-04 07:00:34... | 2016-02-04 07:47:09 UTC | 221     |
+----+------------+------------------------+-------------------------+---------+
1 row in set
2.2.3 :011 > a = Comment.where("post_id = 221").pluck("body")
   (0.5ms)  SELECT "comments"."body" FROM "comments" WHERE (post_id = 221)
[
    [0] "comment123"
]
2.2.3 :012 > a = Comment.where(post_id: 221).pluck(:body, :updated_at)
   (0.2ms)  SELECT "comments"."body", "comments"."updated_at" FROM "comments" WHERE "comments"."post_id" = $1  [["post_id", 221]]
[
    [0] [
        [0] "comment123",
        [1] Thu, 04 Feb 2016 07:47:09 UTC +00:00
    ]
]
2.2.3 :013 > column_names = [:body, :updated_at]
[
    [0] :body,
    [1] :updated_at
]
2.2.3 :014 > a = Comment.where(post_id: 221).pluck(*column_names)
   (0.4ms)  SELECT "comments"."body", "comments"."updated_at" FROM "comments" WHERE "comments"."post_id" = $1  [["post_id", 221]]
[
    [0] [
        [0] "comment123",
        [1] Thu, 04 Feb 2016 07:47:09 UTC +00:00
    ]
]
2.2.3 :015 > Hash[column_names.zip(a[0])]
{
          :body => "comment123",
    :updated_at => Thu, 04 Feb 2016 07:47:09 UTC +00:00
}
2.2.3 :016 > a = Comment.where(post_id: 221).pluck(*column_names)
   (0.5ms)  SELECT "comments"."body", "comments"."updated_at" FROM "comments" WHERE "comments"."post_id" = $1  [["post_id", 221]]
[
    [0] [
        [0] "comment123",
        [1] Thu, 04 Feb 2016 07:47:09 UTC +00:00
    ]
]
2.2.3 :017 > a.map{|x| Hash[column_names.zip(x)]}
[
    [0] {
              :body => "comment123",
        :updated_at => Thu, 04 Feb 2016 07:47:09 UTC +00:00
    }
]