init project

app/services/admins/drag_weapp_carousel_service.rb

@@ -0,0 +1,32 @@
+class Admins::DragWeappCarouselService < ApplicationService
+  attr_reader :move, :after
+
+  def initialize(move, after)
+    @move  = move
+    @after = after # 移动后下一个位置的元素
+  end
+
+  def call
+    return if move.position + 1 == after&.position # 未移动
+
+    carousels = WeappSettings::Carousel.all
+
+    ActiveRecord::Base.transaction do
+      if after.blank? || move.id == after.id # 移动至末尾
+        total = carousels.count
+
+        carousels.where('position > ?', move.position).update_all('position = position - 1')
+        move.update!(position: total)
+        return
+      end
+
+      if move.position > after.position # 前移
+        carousels.where('position >= ? AND position < ?', after.position, move.position).update_all('position = position + 1')
+        move.update!(position: after.position)
+      else # 后移
+        carousels.where('position > ? AND position < ?', move.position, after.position).update_all('position = position - 1')
+        move.update!(position: after.position - 1)
+      end
+    end
+  end
+end