错误：验证失败：可成像的图像必须存在，rails-5.0，paperclip-5

当我尝试提交表单时，发生以下错误：Validation failed: Images imageable must exist并渲染相同的new.html.erb view.

如果我评论file field in new.html.erb。产品正在成功创建。

产品控制器：

def new
    @product = Product.new
end

def create
    @product = Product.create!(product_params)

    if @product.save
        redirect_to products_path, notice: "Product Created Successfully"
    else
        render "new"
    end
end
def product_params
        params.require(:product).permit(:name, :quantity, :price, images_attributes: [:id, :photo, :_destroy])
end

新的.html.erb：

<%= nested_form_for @product, html: { multipart: true } do |f|%>

    <h2>New</h2>

    <P> <%= f.label :name %> <%= f.text_field :name %> </P>
    <P> <%= f.label :quantity %> <%= f.text_field :quantity %> </P>
    <P> <%= f.label :price %> <%= f.text_field :price %> </P>
  <%= f.fields_for :images do |p| %>
    <p> <%= p.label :photo %> <%= p.file_field :photo %> </p>
    <%= p.link_to_remove "Remove Image" %>
  <% end %>
  <%= f.link_to_add "Add Image", :images %>

  <%= f.submit "Add Product" %>
<% end %>

20160725102038_add_image_columns_to_imageable.rb：

class AddImageColumnsToImageable < ActiveRecord::Migration[5.0]

  def up
    add_attachment :images, :photo
  end

  def down
    remove_attachment :images, :photo
  end

end

型号：product.rb

class Product < ApplicationRecord
    has_one :variant
  has_many  :images, as: :imageable,  dependent: :destroy

  accepts_nested_attributes_for :images, allow_destroy: true
end

型号：image.rb

class Image < ApplicationRecord
  belongs_to :imageable, polymorphic: true

  has_attached_file :photo, styles: { medium: "300x300>", thumb: "100x100>" }, default_url: "/images/:style/missing.png"
  validates_attachment :photo, content_type: { content_type: ["image/jpg", "image/jpeg", "image/png", "image/gif"] }

end

在轨道 5 中，belongs_to确保关联的模型必须存在。 例如，在这种多态关联中，图像模型具有belongs_to :imageable并且产品型号有has_many :images。 所以在这里new.html.erb我们正在创建图像，但相应的产品不存在，所以这就是错误的原因Image imageable must exist .

Solution

Add optional: true在建立关联时belong_to在图像模型中。

图像模型现在看起来像：

class Image < ApplicationRecord
  belongs_to :imageable, polymorphic: true, optional: true

  has_attached_file :photo, styles: { medium: "300x300>", thumb: "100x100>" }, default_url: "/images/:style/missing.png"
  validates_attachment :photo, content_type: { content_type: ["image/jpg", "image/jpeg", "image/png", "image/gif"] }

end