Ruby on Rails-从最后一个对象增加1

Question

I am building a user gallery application, where user can create albums and upload images to their album. I am using nested forms for images.

In my images database, I have a column called sort_order . I want to use sort_order to manage the sorting and showing user, for ex: he is seeing 3 of 12 images, where 3 is number of sort_order and 12 is number of total images in that album.

sort_order is integer and default: 0 . What I looking for is to increase/ increment number of sort_order for each image based on previous sort_order of last image in same album.

For ex: image 1 will have sort_order: 1 , image 2 will then have previous images sort_id +1 => sort_order: 2 and so on.

Here is the code I am using now:

after_create :previous_image

  def previous_image

    img = user.images.order("id ASC")

    img.each do |image|
      image.increment!(:sort_order, self.sort_order + 1)
    end

  end

This does the work but in wrong sort.

id      sort_order
10          3
11          2
12          1

instead of having, id: 10 sort_order: 1 , its getting 3 .

This is the log:

  SQL (0.5ms)  UPDATE "images" SET "sort_order" = ?, "updated_at" = ? WHERE "images"."id" = ?  [["sort_order", 1], ["id", 398]]

  user Load (0.1ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = ? LIMIT 1  [["id", 160]]

  Slide Load (0.1ms)  SELECT "images".* FROM "images" WHERE "images"."user_id" = ?  ORDER BY id DESC  [["user_id", 160]]

  SQL (0.1ms)  UPDATE "images" SET "sort_order" = ?, "updated_at" = ? WHERE "images"."id" = ?  [["sort_order", 1], ["id", 399]]

  SQL (0.1ms)  UPDATE "images" SET "sort_order" = ?, "updated_at" = ? WHERE "images"."id" = ?  [["sort_order", 2], ["id", 398]]

  user Load (0.2ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = ? LIMIT 1  [["id", 160]]

  Slide Load (0.1ms)  SELECT "images".* FROM "images" WHERE "images"."user_id" = ?  ORDER BY id DESC  [["user_id", 160]]

  SQL (0.1ms)  UPDATE "images" SET "sort_order" = ?, "updated_at" = ? WHERE "images"."id" = ?  [["sort_order", 1], ["id", 400]]

  SQL (0.1ms)  UPDATE "images" SET "sort_order" = ?, "updated_at" = ? WHERE "images"."id" = ?  [["sort_order", 2], ["id", 399]]

  SQL (0.1ms)  UPDATE "images" SET "sort_order" = ?, "updated_at" = ? WHERE "images"."id" = ?  [["sort_order", 3], ["id", 398]]

It starts from bottom and not top. How can I fix it?

If there is another way to do it without having the sort_order column, I am open to it.

Answer 1

After receiving the form data, add an index (starting from 1) to the images array.

Considering this is your images array from the form:

images = [{name: 'Image 1', data: 123}, {name: 'Image 2', data: 456}]

Use with_index(1) to attach the sort order to every element:

images.map.with_index(1).to_a

=> [[{:name=>"Image 1", :data=>123}, 1], [{:name=>"Image 2", :data=>456}, 2]]