blocks|key|1439567|text|id只是attr_protected，这就是为什么你不能使用批量赋值来设置它的原因。但是，当手动设置时，它只起作用：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1439568|o+=+SomeObject.new
o.id+=+8888
o.save!
o.reload.id+#+=>+8888|code-block|syntax|javascript|1439569|我不确定最初的动机是什么，但我在将ActiveHash模型转换为ActiveRecord时会这样做。ActiveHash允许您在ActiveRecord中使用相同的belongs_to语义，但是您只需将数据存储在yml文件中，而不是进行迁移和创建表，并且在每次调用时都会产生数据库开销。数据库中的外键引用yml中的内存ids。|1439570|ActiveHash对于选择列表和较小的表来说是很棒的，这些表很少更改，并且只由开发人员更改。因此，当从ActiveHash转换到ActiveRecord时，最简单的方法就是保持所有外键引用相同。|1439571|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

id is just attr_protected, which is why you can't use mass-assignment to set it. However, when setting it manually, it just works:

<pre><code>o = SomeObject.new
o.id = 8888
o.save!
o.reload.id # =&gt; 8888
</code></pre>

I'm not sure what the original motivation was, but I do this when converting ActiveHash models to ActiveRecord. ActiveHash allows you to use the same belongs_to semantics in ActiveRecord, but instead of having a migration and creating a table, and incurring the overhead of the database on every call, you just store your data in yml files. The foreign keys in the database reference the in-memory ids in the yml.

ActiveHash is great for picklists and small tables that change infrequently and only change by developers. So when going from ActiveHash to ActiveRecord, it's easiest to just keep all of the foreign key references the same.

blocks|key|1439777|text|你也可以使用类似这样的东西：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1439778|Post.create({:id+=>+10,+:title+=>+'Test'},+:without_protection+=>+true)|code-block|syntax|javascript|1439779|尽管如docs中所述，这将绕过批量赋值安全性。|offset|length|1439780|entityMap|0|LINK|mutability|MUTABLE|url|http://api.rubyonrails.org/classes/ActiveRecord/Persistence/ClassMethods.html#method-i-create^0|0|0|3|4|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@$I|V|J|W|1|X]]|A|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

You could also use something like this:

<pre><code>Post.create({:id =&gt; 10, :title =&gt; 'Test'}, :without_protection =&gt; true)
</code></pre>

Although as stated in the <a href="http://api.rubyonrails.org/classes/ActiveRecord/Persistence/ClassMethods.html#method-i-create" rel="noreferrer">docs</a>, this will bypass mass-assignment security.

blocks|key|1654214|text|试一试|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1654215|a_post+=+Post.new+do+%7Cp%7C+
++p.id+=+10
++p.title+=+'Test'
++p.save
end|code-block|syntax|javascript|1654216|这应该会给你你想要的东西。|1654217|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Try 

<pre><code>a_post = Post.new do |p| 
 p.id = 10
 p.title = 'Test'
 p.save
end
</code></pre>

that should give you what you're looking for.

blocks|key|1439666|text|我们可以覆盖attributes_protected_by_default|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1439667|class+Example+<+ActiveRecord::Base
++++def+self.attributes_protected_by_default
++++++++#+default+is+["id",+"type"]
++++++++["type"]
++++end
end

e+=+Example.new(:id+=>+10000)|code-block|syntax|javascript|1439668|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

we can override attributes_protected_by_default

<pre><code>class Example &lt; ActiveRecord::Base
 def self.attributes_protected_by_default
 # default is ["id", "type"]
 ["type"]
 end
end

e = Example.new(:id =&gt; 10000)
</code></pre>

blocks|key|1439522|text|实际上，事实证明，这样做是有效的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1439523|p+=+Post.new(:id+=>+10,+:title+=>+'Test')
p.save(false)|code-block|syntax|javascript|1439524|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Actually, it turns out that doing the following works:

<pre><code>p = Post.new(:id =&gt; 10, :title =&gt; 'Test')
p.save(false)
</code></pre>

blocks|key|1654363|text|正如杰夫指出的，id的行为就像是attr_protected一样。为了防止出现这种情况，您需要覆盖默认的受保护属性列表。在属性信息可能来自外部的任何地方执行此操作时都要小心。id字段是默认保护的，这是有原因的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1654364|class+Post+<+ActiveRecord::Base

++private

++def+attributes_protected_by_default
++++[]
++end
end|code-block|syntax|javascript|1654365|(使用ActiveRecord+2.3.5测试)|1654366|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

As Jeff points out, id behaves as if is attr_protected. To prevent that, you need to override the list of default protected attributes. Be careful doing this anywhere that attribute information can come from the outside. The id field is default protected for a reason.

<pre><code>class Post &lt; ActiveRecord::Base

 private

 def attributes_protected_by_default
 []
 end
end
</code></pre>

(Tested with ActiveRecord 2.3.5)

blocks|key|1439741|text|Post.create!(:title+=>+"Test")+{+%7Ct%7C+t.id+=+10+}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1439742|在我看来，这并不是您通常想要做的事情，但如果您需要用一组固定的is来填充一个表(例如，当使用rake任务创建默认值时)，并且您想要覆盖自动递增(这样每次运行任务时，都会用相同的is填充该表)，那么它就能很好地工作：|unstyled|1439743|post_types.each_with_index+do+%7Cpost_type%7C
++PostType.create!(:name+=>+post_type)+{+%7Ct%7C+t.id+=+i+%2B+1+}
end|1439744|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|L|8|@]|9|@]|A|$]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$B|C]]|$1|I|3|-4|5|F|7|N|8|@]|9|@]|A|$]]]|J|$]]

<pre><code>Post.create!(:title =&gt; "Test") { |t| t.id = 10 }
</code></pre>

This doesn't strike me as the sort of thing that you would normally want to do, but it works quite well if you need to populate a table with a fixed set of ids (for example when creating defaults using a rake task) and you want to override auto-incrementing (so that each time you run the task the table is populate with the same ids):

<pre><code>post_types.each_with_index do |post_type|
 PostType.create!(:name =&gt; post_type) { |t| t.id = i + 1 }
end
</code></pre>

blocks|key|1439834|text|这种情况是一个类似的问题，需要用一种自定义日期覆盖id：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1439835|#+in+app/models/calendar_block_group.rb
class+CalendarBlockGroup+<+ActiveRecord::Base
...
+before_validation+:parse_id

+def+parse_id
++++self.id+=+self.date.strftime('%25d%25m%25Y')
+end
...
end|code-block|syntax|javascript|1439836|然后：|1439837|CalendarBlockGroup.create!(:date+=>+Date.today)
#+=>+#<CalendarBlockGroup+id:+27072014,+date:+"2014-07-27",+created_at:+"2014-07-27+20:41:49",+updated_at:+"2014-07-27+20:41:49">|1439838|回调工作得很好。|1439839|祝你好运！|1439840|entityMap^0|P|2|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|Y|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|Z|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|10|8|@]|D|@]|E|$]]|$1|Q|3|R|5|6|7|11|8|@]|D|@]|E|$]]|$1|S|3|-4|5|6|7|12|8|@]|D|@]|E|$]]]|T|$]]

This case is a similar issue that was necessary overwrite the <code>id</code> with a kind of custom date :

<pre><code># in app/models/calendar_block_group.rb
class CalendarBlockGroup &lt; ActiveRecord::Base
...
 before_validation :parse_id

 def parse_id
 self.id = self.date.strftime('%d%m%Y')
 end
...
end
</code></pre>

And then :

<pre><code>CalendarBlockGroup.create!(:date =&gt; Date.today)
# =&gt; #&lt;CalendarBlockGroup id: 27072014, date: "2014-07-27", created_at: "2014-07-27 20:41:49", updated_at: "2014-07-27 20:41:49"&gt;
</code></pre>

Callbacks works fine.

Good Luck!.

blocks|key|1654629|text|对于Rails3，最简单的方法是使用带有without_protection精化的new，然后使用save|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1654630|Post.new({:id+=>+10,+:title+=>+'Test'},+:without_protection+=>+true).save|code-block|syntax|javascript|1654631|对于种子数据，绕过验证可能是有意义的，您可以这样做：|1654632|Post.new({:id+=>+10,+:title+=>+'Test'},+:without_protection+=>+true).save(validate:+false)|1654633|我们实际上已经向ActiveRecord::Base添加了一个帮助器方法，它是在执行种子文件之前声明的：|1654634|class+ActiveRecord::Base
++def+self.seed_create(attributes)
++++new(attributes,+without_protection:+true).save(validate:+false)
++end
end|1654635|现在：|1654636|Post.seed_create(:id+=>+10,+:title+=>+'Test')|1654637|对于Rails4，您应该使用StrongParams而不是受保护的属性。如果是这种情况，您将能够简单地分配和保存，而无需将任何标志传递给new|1654638|Post.new(id:+10,+title:+'Test').save++++++#+optionally+pass+`{validate:+false}`|1654639|entityMap^0|K|I|15|3|1D|4|0|0|0|0|0|0|0|0|1W|3|0|0^^$0|@$1|2|3|4|5|6|7|12|8|@$9|13|A|14|B|C]|$9|15|A|16|B|C]|$9|17|A|18|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|19|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|1A|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|1B|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|1C|8|@]|D|@]|E|$]]|$1|Q|3|R|5|H|7|1D|8|@]|D|@]|E|$I|J]]|$1|S|3|T|5|6|7|1E|8|@]|D|@]|E|$]]|$1|U|3|V|5|H|7|1F|8|@]|D|@]|E|$I|J]]|$1|W|3|X|5|6|7|1G|8|@$9|1H|A|1I|B|C]]|D|@]|E|$]]|$1|Y|3|Z|5|H|7|1J|8|@]|D|@]|E|$I|J]]|$1|10|3|-4|5|6|7|1K|8|@]|D|@]|E|$]]]|11|$]]

For Rails 3, the simplest way to do this is to use <code>new</code> with the <code>without_protection</code> refinement, and then <code>save</code>:

<pre><code>Post.new({:id =&gt; 10, :title =&gt; 'Test'}, :without_protection =&gt; true).save
</code></pre>

For seed data, it may make sense to bypass validation which you can do like this:

<pre><code>Post.new({:id =&gt; 10, :title =&gt; 'Test'}, :without_protection =&gt; true).save(validate: false)
</code></pre>

We've actually added a helper method to ActiveRecord::Base that is declared immediately prior to executing seed files:

<pre><code>class ActiveRecord::Base
 def self.seed_create(attributes)
 new(attributes, without_protection: true).save(validate: false)
 end
end
</code></pre>

And now:

<pre><code>Post.seed_create(:id =&gt; 10, :title =&gt; 'Test')
</code></pre>

For Rails 4, you should be using StrongParams instead of protected attributes. If this is the case, you'll simply be able to assign and save without passing any flags to <code>new</code>:

<pre><code>Post.new(id: 10, title: 'Test').save # optionally pass `{validate: false}`
</code></pre>

blocks|key|1439954|text|在带有PostgreSQL9.5.3的Rails+4.2.1中，只要没有id+=+10的行，Post.create(:id+=>+10,+:title+=>+'Test')就可以工作。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1439955|entityMap^0|1A|14|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

In Rails 4.2.1 with Postgresql 9.5.3, <code>Post.create(:id =&gt; 10, :title =&gt; 'Test')</code> works as long as there isn't a row with id = 10 already.

blocks|key|1439967|text|您可以通过sql插入id：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1439968|++arr+=+record_line.strip.split(",")
++sql+=+"insert+into+records(id,+created_at,+updated_at,+count,+type_id,+cycle,+date)+values(#{arr[0]},#{arr[1]},#{arr[2]},#{arr[3]},#{arr[4]},#{arr[5]},#{arr[6]})"
++ActiveRecord::Base.connection.execute+sql|code-block|syntax|javascript|1439969|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

you can insert id by sql:

<pre><code> arr = record_line.strip.split(",")
 sql = "insert into records(id, created_at, updated_at, count, type_id, cycle, date) values(#{arr[0]},#{arr[1]},#{arr[2]},#{arr[3]},#{arr[4]},#{arr[5]},#{arr[6]})"
 ActiveRecord::Base.connection.execute sql
</code></pre>

Is there any way of overriding a model's id value on create? Something like:

<pre><code>Post.create(:id =&gt; 10, :title =&gt; 'Test')
</code></pre>

would be ideal, but obviously won't work.

Overriding id on create in ActiveRecord

有没有办法在create上覆盖模型的id值？类似于：Post.create(:id => 10, :title => 'Test')将是理想的，但显然不会工作。

问在ActiveRecord中create时覆盖id
EN

回答 11

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