Question

我所指的具体实例就在这里。我想使用Grid表中的一行作为Driver表中Grid属性的值。但我无法在Grid表中获取更新以持久保存到Driver表上的Grid属性我想使用Race表中的一行作为Driver表中Race属性的值。

以下是datamapper内容的代码。

require "rubygems"
require "json"
require "sinatra"
require "sinatra/reloader"
require "sqlite3"
require "data_mapper"

DataMapper::setup(:default, "sqlite3://#{Dir.pwd}/season.db")


class Driver
    include DataMapper::Resource
    property :id, String, :key => true
    property :ptd, Integer
    property :races, Integer
    property :grid, Object
    property :race, Object
    property :hcScore, Integer
    property :domScore, Integer
end

class Grid
    include DataMapper::Resource
    property :id, String, :key => true
    property :AUS_Q, Integer
    property :MAL_Q, Integer
    property :CHI_Q, Integer
    property :BAH_Q, Integer
end

class Race
    include DataMapper::Resource
    property :id, String, :key => true
    property :AUS_R, Integer
    property :MAL_R, Integer
    property :CHI_R, Integer
    property :BAH_R, Integer
end

class Team

    include DataMapper::Resource
    property :id, String, :key =>  true
    property :domScore, Integer
    property :drivers, Object
end

DataMapper.finalize.auto_migrate!

在irb我会做类似

的事情

irb(main):001:0> require "./season.rb"
=> true
irb(main):002:0> v = Driver.create id: "VET"
=> #<Driver @id="VET" @ptd=nil @races=nil @grid=nil @race=nil @hcScore=nil @domScore=nil>
irb(main):003:0> g = Grid.create id: "VET"
=> #<Grid @id="VET" @AUS_Q=nil @MAL_Q=nil @CHI_Q=nil @BAH_Q=nil>
irb(main):004:0> v.grid = Grid.get "VET"
=> #<Grid @id="VET" @AUS_Q=nil @MAL_Q=nil @CHI_Q=nil @BAH_Q=nil>
irb(main):005:0> v.save
=> true
irb(main):006:0> g.update(:AUS_Q => 6)
=> true
irb(main):007:0> v
=> #<Driver @id="VET" @ptd=nil @races=nil @grid=#<Grid @id="VET" @AUS_Q=nil @MAL_Q=nil @CHI_Q=nil @BAH_Q=nil> @race=nil @hcScore=nil @domScore=nil>
irb(main):008:0> Grid.get "VET"
=> #<Grid @id="VET" @AUS_Q=6 @MAL_Q=nil @CHI_Q=nil @BAH_Q=nil>
irb(main):009:0> AUS_Q = 6 in the Grid table but in the Driver table it continues to be nil!

如您所见 - 即使我在网格表中将其设置为6，Driver表中的AUS_Q仍为零。

我有可能做错了，有一种更简单的方法可以做到这一点。我鼓励所有纠正和打击。

Answer 1

我建议您使用belongs_to创建资源之间的关联，并使用身份映射，如下所示：

require "sqlite3"
require "data_mapper"

class Driver
    include DataMapper::Resource
    property :id, String, :key => true
    belongs_to :grid, :required => false
end

class Grid
    include DataMapper::Resource
    property :id, String, :key => true
    property :AUS_Q, Integer
end

DataMapper::setup(:default, "sqlite3://#{Dir.pwd}/season.db")
DataMapper.finalize.auto_migrate!

DataMapper.repository(:default) do
  v = Driver.create id: "VET"
  g = Grid.create id: "VET"
  v.grid = Grid.get "VET"
  v.save
  g.update(:AUS_Q => 6)
  puts v.grid.AUS_Q
  puts Grid.get("VET").AUS_Q
end

您在DataMapper.repository(:default) do发起的阻止中执行的所有操作都将使用身份地图。因此，数据库中的相同对象将在内存中产生相同的对象。

如何使用Datamapper将一个表中的行用作另一个表中的属性？

1 个答案: