0

我在 Rails 中使用 DataMapper，替换 ActiveRecord 并尝试做一些单表继承。问题是，sqlite3 似乎正在奇怪地读取我所有继承的表，因此在尝试在 ruby​​ 中创建该表的实例时出现一些奇怪的错误。

我正在使用一个模型 ServerFile 来表示我想在我的数据库中实例化的任何上传或通用文件。我有另一个模型 Upload，它扩展了它并表示来自用户的 Upload。我还有两个从 ServerFile、Thumbnail 和 UploadThumbnail 扩展的模型，分别表示一个通用的 Thumbnail 和一个用于相应上传的 Thumbnail。

我不断收到的错误是DataObjects::IntegrityError (server_files.upload_id may not be NULL)当我尝试创建这样的 Upload 实例时：

upload = Upload.new(
    filename: uploaded_io.original_filename, 
    path: path.to_s, 
    content_type: uploaded_io.content_type, 
    token: rand_token())

upload.member = @member
upload.title = params[:title]
upload.description = params[:description]
upload.save

这是我的模型：

class ServerFile
    include DataMapper::Resource
    property :id, Serial
    property :token, String, unique_index: true
    property :filename, String
    property :path, Text, unique: true
    property :content_type, Text, length: 5..200
    property :type, Discriminator

    property :created_on, Date
    property :created_at, DateTime
    property :updated_on, Date
    property :updated_at, DateTime
end

class Upload < ServerFile
    property :title, String
    property :description, Text

    has n, :topics, through: Resource
    has n, :subjects, through: Resource
    has n, :downloads
    has n, :comments, 'UploadComment'
    has n, :ratings, 'UploadRating'

    belongs_to :member
    has 1, :thumbnail, 'UploadThumbnail', required: false
end

class Thumbnail < ServerFile
    @@IMAGE_EXTENSIONS = [:'png', :'jpg', :'jpeg', :'gif', :'svg', :'cgm']
    validates_with_method :filename, :is_valid_image?

    def is_valid_image?
        @@IMAGE_EXTENSIONS.each do |ext|
            return true if /[\w\d\.\_\-]+\.#{ext.to_s}/ =~ @filename
        end
        [false, 'Invalide image type.']
    end
end

class UploadThumbnail < Thumbnail
    belongs_to :upload
end

这是我的表'server_files'的sqlite模式（顺便说一句，当我列出我的表时，其中没有列出'uploads'）：

sqlite> .schema server_files
CREATE TABLE "server_files" ("id" INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT, "token" VARCHAR(50), "filename" VARCHAR(50), "path" TEXT, "content_type" TEXT, "type" VARCHAR NOT NULL, "created_on" DATE, "created_at" TIMESTAMP, "updated_on" DATE, "updated_at" TIMESTAMP, "title" VARCHAR(50), "description" TEXT, "member_id" INTEGER NOT NULL, "upload_id" INTEGER NOT NULL);
CREATE UNIQUE INDEX "unique_server_files_path" ON "server_files" ("path");
CREATE UNIQUE INDEX "unique_server_files_token" ON "server_files" ("token");
4

2 回答 2

0

桌子上不需要一upload_id列server_files。因为Upload继承自ServerFile，所以这本质上是自引用的。模型保存成功后，将在数据库中设置type类型为的列。话虽如此，如果你想设置一个自定义的upload_id，你可以用这样的回调来做到这一点：DiscriminatorUpload

before :create, :generate_upload_id

def generate_upload_id
  generated_upload_id = <do something>
  attribute_set(:upload_id, generated_upload_id) unless upload_id
end

否则，只需编写一个从 server_files 表中删除 upload_id 列的迁移

来源：http ://datamapper.org/docs/misc.html

于 2013-08-04T16:38:20.890 回答
0

出于某种原因，DataMapper 不喜欢我的超类 ServerFile。当我打破它时，它工作得很好！（：

class Upload < ServerFile
    include DataMapper::Resource
    property :id, Serial
    property :token, String, unique_index: true
    property :filename, String
    property :path, Text, unique: true
    property :content_type, Text, length: 5..200

    property :created_on, Date
    property :created_at, DateTime
    property :updated_on, Date
    property :updated_at, DateTime
    property :title, String
    property :description, Text

    has n, :topics, through: Resource
    has n, :subjects, through: Resource
    has n, :downloads
    has n, :comments, 'UploadComment'
    has n, :ratings, 'UploadRating'

    belongs_to :member
    has 1, :thumbnail, 'UploadThumbnail', required: false
end

class Thumbnail < ServerFile
    include DataMapper::Resource
    property :id, Serial
    property :token, String, unique_index: true
    property :filename, String
    property :path, Text, unique: true
    property :content_type, Text, length: 5..200
    property :type, Discriminator

    property :created_on, Date
    property :created_at, DateTime
    property :updated_on, Date
    property :updated_at, DateTime

    @@IMAGE_EXTENSIONS = [:'png', :'jpg', :'jpeg', :'gif', :'svg', :'cgm']
    validates_with_method :filename, :is_valid_image?

    def is_valid_image?
        @@IMAGE_EXTENSIONS.each do |ext|
            return true if /[\w\d\.\_\-]+\.#{ext.to_s}/ =~ @filename
        end
        [false, 'Invalide image type.']
    end
end

class UploadThumbnail < Thumbnail
    belongs_to :upload
end
于 2013-08-06T15:12:56.377 回答