遇到问题 ActiveRecord::EagerLoadPoly

参考：https://api.rubyonrails.org/v5.1/classes/ActiveRecord/EagerLoadPolymorphicError.html

https://api.rubyonrails.org/v5.1/classes/ActiveRecord/QueryMethods.html#method-i-preload

报错代码：

@orders = Order.all
@orders = @orders.joins(:user).merge(User.with_level(params[:level])) if params[:level].in? Order.level.values
@orders = @orders.includes(:user, :orderable).recent.paginate(page: params[:page], per_page: 30)

解决问题：

@orders = Order.all
@orders = @orders.joins(:user).merge(User.with_level(params[:level])) if params[:level].in? Order.level.values
@orders = @orders.preload(:user, :orderable).recent.paginate(page: params[:page], per_page: 30)