ruby datamapper不能保存到数据库。

I have a database schema like that

我有一个这样的数据库模式

DataMapper.setup :default, "sqlite://#{Dir.pwd}/image.db"
class Image
    include DataMapper::Resource

    property :id       , Serial
    property :url , String,unique: true
    property :desc    , String,unique: true,default: "empty"
end
DataMapper.finalize.auto_upgrade!

Then i have a loop like this

然后有一个这样的循环。

links.each do |link|
  puts link
  if Image.all(:url=>link).empty? == true
    img=Image.create(:url => link)
    puts "Cannot save to database "if img.saved? == false
  end
end

I want to add a link when it is not already in a database. I run the script and always get cannot save to dabase. What am I doing wrong? Thanks for any help. Edit: I add to my code

当链接不在数据库中时，我想添加它。我运行脚本，总是无法保存到dabase。我做错了什么?感谢任何帮助。编辑:我添加了我的代码。

DataMapper::Logger.new($stdout, :debug)

and there was no insert queries only selects.

没有插入查询，只有选择。

2 个解决方案

#1

You declared :desc property to be unique and set default value to "empty" and in your code example you're creating Image without specifying :desc which results in uniqueness validation failure, that's why your images aren't saved. You can either remove unique option from :desc property declaration or make sure to provide unique value for :desc when creating images.

您声明:desc属性为唯一，并将默认值设置为“empty”，在您的代码示例中，您在创建映像时没有指定:desc，这将导致惟一验证失败，这就是为什么您的映像没有保存。您可以从:desc属性声明中删除惟一选项，或者在创建映像时确保为:desc提供惟一值。

Also, to make your code more verbose so you could see any validation errors try this:

另外，要使代码更加冗长，以便您可以看到任何验证错误，请尝试以下方法:

links.each do |link|
  image = Image.new(:url => link)

  if image.save
    puts "Image saved"
  else
    puts "Failed to save image: #{image.errors.inspect}"
  end
end

Please note that to use validation errors you need to require 'dm-validations' gem.

请注意，要使用验证错误，需要使用“dm验证”gem。

#2

What do you mean you get "cannot save to database"?

你说的“无法保存到数据库”是什么意思?

You can try something like this and see if it works a bit better:

你可以试试这样的方法，看看效果是否更好:

links.each do |link|
  if Image.first(:url => link)
    p "image exists"
  else
    if Image.create(:url => link) 
      p "Image succesfully saved"
    else
      p "could not save image"
    end
  end
end

#1