Question

我实施它的方式似乎不是。

在data_mapper术语中 - 我有一个加入资源条目，它加入了Driver，Team和Season

我有一个加入Track and Season的加入资源Race

我有一个加入资源Placing加入Entry和Race。

当我尝试做某些事情时“向我展示一个特定参赛作品参与的所有比赛

@entry_a.races.all

我收到此错误

DataObjects :: SyntaxError：没有这样的列：INNER（代码：1，sql state :, query：SELECT“races”。“track_id”，“races”。“season _id“，”比赛“。”race_no“FROM”比赛“INNER JOIN”位置“ON INNER JOIN”条目“ON”位置“。”entry_team_id“=”ent ries“。”team_id“AND”placings“。”entry_driver_id“=”entries“。”driver_id“WHERE（”placings“。”entry_team_id“='FER'AND” placings“。”entry_driver_id“='MAS'）GROUP BY”races“。”track_id“，”races“。”season_id“，”races“。”race_no“ORDER BY”种族 “。”track_id“，”races“。”season_id“，uri：sqlite3：C / devProjects / formula1 ../ spec / resources / test.db？scheme = sqlite3＆amp; user =＆amp; pas 剑=安培;主机= C＆安培;端口=安培;查询=安培;片段=安培;适配器= sqlite3的＆安培;路径= / devProjects /一级方程式../规格/资源/ test.db的）

很容易看到这里发生的事情，.all方法包装的查询不期望加入连接。

我设法通过编写一些自定义sql来解决这个问题。虽然不理想，但它确实能够胜任。它似乎不是红宝石的方式。也许我的db架构糟透了？

这是我的模型（对于代码转储感到抱歉。我已经被一个SO的同事烧死了，因为我没有引用完整的代码而决定投票给我）

require "rubygems"
require "sqlite3"
require "data_mapper"
require "bigdecimal"

#note that Dir.pwd refers to the location of the file that calls
if ENV["run_mode"] == "prod"
    DataMapper::setup(:default, "sqlite3://#{Dir.pwd}/data/prod.db")
else
    DataMapper::setup(:default, "sqlite3://#{Dir.pwd}../spec/resources/test.db")
end

class Entry

    include DataMapper::Resource

    belongs_to :team,   :key => true
    belongs_to :driver, :key => true
    belongs_to :season, :key => true

    has n, :placings
    has n, :races, :through => :placings

    def find_races

        return repository.adapter.select('SELECT races.track_id, races.season_id, races.race_no FROM races INNER JOIN placings ON races.track_id = placings.race_track_id INNER JOIN entries ON placings.entry_driver_id = entries.driver_id WHERE (entries.team_id = ? AND entries.driver_id = ?)', self[:team_id], self[:driver_id])

    end

end

class Track

    include DataMapper::Resource

    property :id, String, :key => true

    has n, :races

end

class Race

    include DataMapper::Resource

    property :race_no, Integer

    belongs_to :track,  :key => true
    belongs_to :season, :key => true

    has n, :placings
    has n, :entries, :through => :placings


end

class Placing

    include DataMapper::Resource

    property :id, Serial #put this in because dm was complaining that foreign keys from entry object were not unique
    belongs_to :race    
    belongs_to :entry

end

class Season

    include DataMapper::Resource
    property :id, Integer, :key => true

    has n, :races
    has n, :entries

end

class Driver

    include DataMapper::Resource
    property :id, String, :key => true
    property :team, String
    property :ptd, Integer
    property :races, Integer
    property :grid, Object
    property :race, Object
    property :cumulativePoints, Object #the number of points accumulated at a particular point in the season
    property :hcScore, Integer
    property :domScore, Integer
    property :nation, String
    property :wins, Integer
    property :podiums, Integer

    has n, :entries
    has n, :teams, :through => :entries

end

class Team
    include DataMapper::Resource
    property :id, String, :key =>  true
    property :name, String
    property :ptd, Integer
    property :domScore, Integer
    property :nation, String

    has n, :entries
    has n, :drivers, :through => :entries

    def initialize(team_id)
        self[:id] = team_id
        self.save!
    end

    def add_driver(driver_id)
        @driver = Driver.create(:id => driver_id)
        Entry.create(:driver => (Driver.get driver_id), :team => self, :season =>  Season.last)
        return @driver
    end

end

class Nation
    include DataMapper::Resource
    property :id, String, :key => true
    property :ptd, Integer
    # could possibly have the drivers, teams and engines here as well
end

if ENV["run_mode"] == "test"
    DataMapper.finalize.auto_migrate!
else
    DataMapper.finalize.auto_upgrade!
end

Answer 1

经过一些测试后，我认为你看到的错误与复合键有关;尝试更改Race的单个Serial键。我认为这是DM中的一个错误。

尝试使用复合键执行Driver.first.races时出现了同样的错误，但只使用了串行密钥：

$KCODE='u'

require 'rubygems'
require 'dm-core'
require 'dm-migrations'

DataMapper::Logger.new($stdout, :debug)
DataMapper.setup(:default, "sqlite::memory:")

class Entry
  include DataMapper::Resource
  #property :id, Serial # maybe also here? Although everything seems to work without
  property :grid, Integer
  property :position, Integer
  belongs_to :driver, :key => true
  belongs_to :race, :key => true
end

class Driver
  include DataMapper::Resource
  property :name, String, :key => true
  has n, :entries
  has n, :races, :through => :entries
  def podiums; entries(:position => (1..3)) end
  def wins; entries(:position => 1) end
end

class Race
  include DataMapper::Resource
  property :id, Serial
  belongs_to :track
  belongs_to :season
  has n, :entries
  has n, :drivers, :through => :entries
end

class Season
  include DataMapper::Resource
  property :year, Integer, :key => true
  has n, :races
end

class Track
  include DataMapper::Resource
  property :name, String, :key => true
  has n, :races
end

DataMapper.finalize.auto_migrate!

Entry.create(
  :driver => Driver.new(:name => "Kimi Räikkönen"),
  :grid   => 7, :position => 1,
  :race   => Race.new(
    :track  => Track.new(:name => "Albert Park"),
    :season => Season.new(:year => 2013)))

我可以一起加入两个加入资源吗？

1 个答案: