想使用更漂亮的分页效果？请参考下列文章：
Mark。
### Step 2:修改app/controllers/admin/categories_controller.rb
打开app/controllers/admin/categories_controller.rb
```ruby app/controllers/admin/categories_controller.rb
class Admin::CategoriesController < Admin::BaseController
before_action :find_root_categories, only: [:new, :create, :edit, :update]
before_action :find_category, only: [:edit, :update, :destroy]
def index
if params[:id].blank? #如果id为空，则说明没二级分类
@categories = Category.roots
else
@category = Category.find(params[:id])
@categories = @category.children #@category.children是ancestry gem自己提供的
end
@categories = @categories.page(params[:page] || 1).per_page(params[:per_page] || 10)
.order(id: "desc")
end
def new
@category = Category.new
end
def create
@category = Category.new(params.require(:category).permit!)
#以哈希类型的属性，必须做一个过滤，防止批量的属性攻击
#permit!意味着与数据库对应的所有的属性都接收，因为这是后台，所以我这样写
#但是这不是一种严格的写法
if @category.save
flash[:notice] = "保存成功"
redirect_to admin_categories_path
else
render action: :new
end
end
def edit
render action: :new
end
def update
@category.attributes = params.require(:category).permit!
if @category.save
flash[:notice] = "修改成功"
redirect_to admin_categories_path
else
render action: :new
end
end
def destroy
if @category.destroy
flash[:notice] = "删除成功"
redirect_to admin_categories_path
else
flash[:notice] = "删除失败"
redirect_to :back
end
end
private
def find_root_categories
@root_categories = Category.roots.order(id: "desc")
end
def find_category
@category = Category.find(params[:id])
end
end
