请参阅以下输出:
1.9.3p194 :001 > player = Player.randomize_for_market
=> #<Player id: nil, name: "Gale Bridges", age: 19, energy: 100, attack: 6, defense: 4, stamina: 5, goal_keeping: 3, power: 4, accuracy: 5, speed: 5, short_pass: 5, ball_controll: 4, long_pass: 6, regain_ball: 5, contract_id: nil, created_at: nil, updated_at: nil>
1.9.3p194 :002 > player.save!
(0.2ms) BEGIN
SQL (20.5ms) INSERT INTO "players" ("accuracy", "age", "attack", "ball_controll", "contract_id", "created_at", "defense", "energy", "goal_keeping", "long_pass", "name", "power", "regain_ball", "short_pass", "speed", "stamina", "updated_at") VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14, $15, $16, $17) RETURNING "id" [["accuracy", 5], ["age", 19], ["attack", 6], ["ball_controll", 4], ["contract_id", nil], ["created_at", Fri, 29 Jun 2012 04:02:34 UTC +00:00], ["defense", 4], ["energy", 100], ["goal_keeping", 3], ["long_pass", 6], ["name", "Gale Bridges"], ["power", 4], ["regain_ball", 5], ["short_pass", 5], ["speed", 5], ["stamina", 5], ["updated_at", Fri, 29 Jun 2012 04:02:34 UTC +00:00]]
(16.6ms) COMMIT
=> true
1.9.3p194 :003 > YAML::load(YAML::dump(Player.randomize_for_market)).save!
(0.2ms) BEGIN
(0.2ms) COMMIT
=> true
为什么会这样,我怎么才能避免呢?
模型上没有((before after)+(save create commit)。我用的是Rails3.2。
Table "public.players"
Column | Type | Modifiers
--------------+-----------------------------+------------------------------------------------------
id | integer | not null default nextval('players_id_seq'::regclass)
name | character varying(255) | not null
age | integer | not null
energy | integer | not null
attack | integer | not null
defense | integer | not null
stamina | integer | not null
goal_keeping | integer | not null
power | integer | not null
accuracy | integer | not null
speed | integer | not null
short_pass | integer | not null
ball_controll | integer | not null
long_pass | integer | not null
regain_ball | integer | not null
contract_id | integer |
created_at | timestamp without time zone | not null
updated_at | timestamp without time zone | not null
Indexes:
"players_pkey" PRIMARY KEY, btree (id)
编辑:回答“你为什么期望yaml::load(yaml::dump(player.randomize_for_market))。保存!做什么?”
因为它序列化一个对象并恢复它?
例子:
1.9.3p194 :006 > p = Player.randomize_for_market
=> #<Player id: nil, name: "Vincenzo Allen", age: 23, energy: 100, attack: 2, defense: 8, stamina: 6, goal_keeping: 3, power: 5, accuracy: 6, speed: 5, short_pass: 6, ball_controll: 5, long_pass: 6, regain_ball: 5, contract_id: nil, created_at: nil, updated_at: nil>
1.9.3p194 :007 > p
=> #<Player id: nil, name: "Vincenzo Allen", age: 23, energy: 100, attack: 2, defense: 8, stamina: 6, goal_keeping: 3, power: 5, accuracy: 6, speed: 5, short_pass: 6, ball_controll: 5, long_pass: 6, regain_ball: 5, contract_id: nil, created_at: nil, updated_at: nil>
1.9.3p194 :008 > YAML::load(YAML::dump(p))
=> #<Player id: nil, name: "Vincenzo Allen", age: 23, energy: 100, attack: 2, defense: 8, stamina: 6, goal_keeping: 3, power: 5, accuracy: 6, speed: 5, short_pass: 6, ball_controll: 5, long_pass: 6, regain_ball: 5, contract_id: nil, created_at: nil, updated_at: nil>
注意p的返回与yaml::load的返回相同
最佳答案
这可能有助于回答您的问题:
:001 > article = Article.new
#<Article:0x102d16b10> { ... }
:002 > article.persisted?
false
:003 > dumped = YAML::dump(article)
"--- !ruby/object:Article ... "
:004 > loaded = YAML::load(dumped)
#<Article:0x102cf5500> { ... }
:005 > loaded.persisted?
true
查看
ActiveRecord::Base#persisted?
的rails源代码:def persisted?
!(new_record? || destroyed?)
end
对于
ActiveRecord::Base#new_record?
:def new_record?
@new_record
end
当您将对象转储到yaml时,
@new_record
实例变量不会被保存,因此当您从yaml加载对象时,它是nil
的。所以activerecord认为它已经被持久化到数据库中,并且没有试图保存它。