迁移数据

db/migrate/20190705011739_add_praises_count_for_challenges.rb

@@ -1,12 +1,5 @@
 class AddPraisesCountForChallenges < ActiveRecord::Migration[5.2]
   def change
-    add_column :challenges, :praises_count, :integer, :default => 0
+    #add_column :challenges, :praises_count, :integer, :default => 0
-
-    challenges = Challenge.where(nil)
-    challenges.each do |c|
-      praises_count = c.praise_tread.where(praise_or_tread: 1).count
-      c.update_column(:praises_count, praises_count)
-    end
-
   end
 end

db/migrate/20190705013203_modify_praises_count_for_challenges.rb

@@ -0,0 +1,9 @@
+class ModifyPraisesCountForChallenges < ActiveRecord::Migration[5.2]
+  def change
+    challenges = Challenge.where(nil)
+    challenges.each do |c|
+      praises_count = c.praise_tread.where(praise_or_tread: 1).count
+      c.update_column(:praises_count, praises_count)
+    end
+  end
+end