Question

我有两个DataMapper模型：

class Address
  include DataMapper::Resource

  property :id, Serial
  property :url, String, :required => true

  has n, :logs
end

class Log
  include DataMapper::Resource

  property :id, Serial
  property :useragent, String

  belongs_to :address
end

我使用Sinatra创建新地址，并使用属于这些地址的另一种方法日志。

  # page after posting a form
  post '/' do
    @messages = []

    if (params[:url] =~ URI::regexp).nil?
      @messages.push('URL is not valid!')
    else
      address = Address.create(:url => params[:url])

      base36 = address.id.to_s(36)
      @messages.push(request.url + base36)
    end

    erb :index
  end

  # redirection from a short url
  get '/:base36' do |base36| 
    # probably not necessary...
    if base36 =~ /[[:alnum:]]+/
      begin
        id = base36.to_i(36)
        address = Address.get(id)

        log = Log.create(:useragent => request.user_agent)
        address.logs << log
        # log.save
        address.save
        # address.logs.save

        address.logs.length.to_s
        # redirect address.url
      rescue
        redirect '/'
      end
    else
      redirect '/'
    end
  end

问题是，新日志不存储在数据库中。 address.logs.length.to_s每个页面重新加载1（它应该递增）。当我这样做时（在另一种方法中）：

logs = Address.get(id).logs
@views = logs.length

views始终为0。这段代码有什么问题？

好的，所以我试着把字符串字段推得太长了。字符串限制为50个字符。 #datamapper irc频道上的人帮助了我，.save方法在这种情况下返回false并且不存储数据。

Answer 1

好的，所以我试着把字符串字段推得太长了。字符串限制为50个字符。 #datamapper irc channel上的人帮我，.save方法在这种情况下返回false，并且不存储数据。

Answer 2

评论说：

address.logs << log
# log.save

但是代码并没有这么说。您应该创建传递地址的日志

log = Log.create(:useragent => request.user_agent, :address => address)

将日志推送到日志集后保存日志：

log = Log.new(:useragent => request.user_agent)
address.logs << log
log.save # not a comment, just a self-explaining code

您案例中的关系存储在Log资源中，因此您应该保存它，而不是Address。

Ruby DataMapper不存储n / belongs_to

2 个答案: