blocks|key|56076|text|更新15.3.2017：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|56077|我已经在这个问题上打开了一个Django问题，它似乎在这里被初步接受：https://code.djangoproject.com/ticket/27825|offset|length|56078|我的经验是，当通过引用在Django+1.10.5中使用Constructor+(ORM)类时，数据中可能会有一些不一致(例如，创建的对象的属性可能会获得输入数据的类型，而不是1.10.5对象属性的强制转换类型)示例：|style|CODE|56079|models|56080|class+Payment(models.Model):
+++++amount_cash+=+models.DecimalField()|code-block|syntax|javascript|56081|some_test.py+-+object.create|56082|Class+SomeTestCase:
++++def+generate_orm_obj(self,+_constructor,+base_data=None,+modifiers=None):
++++++++objs+=+[]
++++++++if+not+base_data:
++++++++++++base_data+=+{'amount_case':+123.00}
++++++++for+modifier+in+modifiers:
++++++++++++actual_data+=+deepcopy(base_data)
++++++++++++actual_data.update(modifier)
++++++++++++#+Hacky+fix,
++++++++++++_obj+=+_constructor.objects.create(**actual_data)
++++++++++++print(type(_obj.amount_cash))+#+Decimal
++++++++++++assert+created
+++++++++++objs.append(_obj)
++++++++return+objs|56083|some_test.py+-+Constructor()|56084|Class+SomeTestCase:
++++def+generate_orm_obj(self,+_constructor,+base_data=None,+modifiers=None):
++++++++objs+=+[]
++++++++if+not+base_data:
++++++++++++base_data+=+{'amount_case':+123.00}
++++++++for+modifier+in+modifiers:
++++++++++++actual_data+=+deepcopy(base_data)
++++++++++++actual_data.update(modifier)
++++++++++++#+Hacky+fix,
++++++++++++_obj+=+_constructor(**actual_data)
++++++++++++print(type(_obj.amount_cash))+#+Float
++++++++++++assert+created
+++++++++++objs.append(_obj)
++++++++return+objs|56085|entityMap|0|LINK|mutability|MUTABLE|url|https://code.djangoproject.com/ticket/27825^0|0|Z|17|0|0|J|6|S|B|15|3|2G|6|0|0|6|0|0|0|C|F|D|0|0|0|C|F|D|0|0^^$0|@$1|2|3|4|5|6|7|16|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|17|8|@]|9|@$D|18|E|19|1|1A]]|A|$]]|$1|F|3|G|5|6|7|1B|8|@$D|1C|E|1D|H|I]|$D|1E|E|1F|H|I]|$D|1G|E|1H|H|I]|$D|1I|E|1J|H|I]]|9|@]|A|$]]|$1|J|3|K|5|6|7|1K|8|@$D|1L|E|1M|H|I]]|9|@]|A|$]]|$1|L|3|M|5|N|7|1N|8|@]|9|@]|A|$O|P]]|$1|Q|3|R|5|6|7|1O|8|@$D|1P|E|1Q|H|I]|$D|1R|E|1S|H|I]]|9|@]|A|$]]|$1|S|3|T|5|N|7|1T|8|@]|9|@]|A|$O|P]]|$1|U|3|V|5|6|7|1U|8|@$D|1V|E|1W|H|I]|$D|1X|E|1Y|H|I]]|9|@]|A|$]]|$1|W|3|X|5|N|7|1Z|8|@]|9|@]|A|$O|P]]|$1|Y|3|-4|5|6|7|20|8|@]|9|@]|A|$]]]|Z|$10|$5|11|12|13|A|$14|15]]]]

UPDATE 15.3.2017:

I have opened a Django-issue on this and it seems to be preliminary accepted here:
<a href="https://code.djangoproject.com/ticket/27825" rel="noreferrer">https://code.djangoproject.com/ticket/27825</a>

My experience is that when using the <code>Constructor</code> (<code>ORM</code>) class by references with Django <code>1.10.5</code> there might be some inconsistencies in the data (i.e. the attributes of the created object may get the type of the input data instead of the casted type of the ORM object property)
example: 

<code>models</code>

<pre><code>class Payment(models.Model):
 amount_cash = models.DecimalField()
</code></pre>

<code>some_test.py</code> - <code>object.create</code>

<pre><code>Class SomeTestCase:
 def generate_orm_obj(self, _constructor, base_data=None, modifiers=None):
 objs = []
 if not base_data:
 base_data = {'amount_case': 123.00}
 for modifier in modifiers:
 actual_data = deepcopy(base_data)
 actual_data.update(modifier)
 # Hacky fix,
 _obj = _constructor.objects.create(**actual_data)
 print(type(_obj.amount_cash)) # Decimal
 assert created
 objs.append(_obj)
 return objs
</code></pre>

<code>some_test.py</code> - <code>Constructor()</code>

<pre><code>Class SomeTestCase:
 def generate_orm_obj(self, _constructor, base_data=None, modifiers=None):
 objs = []
 if not base_data:
 base_data = {'amount_case': 123.00}
 for modifier in modifiers:
 actual_data = deepcopy(base_data)
 actual_data.update(modifier)
 # Hacky fix,
 _obj = _constructor(**actual_data)
 print(type(_obj.amount_cash)) # Float
 assert created
 objs.append(_obj)
 return objs
</code></pre>

blocks|key|56146|text|这两种语法不等价，可能会导致意外错误。这里有一个简单的例子来说明不同之处。如果你有一个模型：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|56147|from+django.db+import+models

class+Test(models.Model):

++++added+=+models.DateTimeField(auto_now_add=True)|code-block|syntax|javascript|56148|然后创建第一个对象：|56149|foo+=+Test.objects.create(pk=1)|56150|然后尝试创建一个具有相同主键的对象：|56151|foo_duplicate+=+Test.objects.create(pk=1)
#+returns+the+error:
#+django.db.utils.IntegrityError:+(1062,+"Duplicate+entry+'1'+for+key+'PRIMARY'")

foo_duplicate+=+Test(pk=1).save()
#+returns+the+error:
#+django.db.utils.IntegrityError:+(1048,+"Column+'added'+cannot+be+null")|56152|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|U|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

The two syntaxes are not equivalent and it can lead to unexpected errors.
Here is a simple example showing the differences.
If you have a model:

<pre><code>from django.db import models

class Test(models.Model):

 added = models.DateTimeField(auto_now_add=True)
</code></pre>

And you create a first object:

<pre><code>foo = Test.objects.create(pk=1)
</code></pre>

Then you try to create an object with the same primary key:

<pre><code>foo_duplicate = Test.objects.create(pk=1)
# returns the error:
# django.db.utils.IntegrityError: (1062, "Duplicate entry '1' for key 'PRIMARY'")

foo_duplicate = Test(pk=1).save()
# returns the error:
# django.db.utils.IntegrityError: (1048, "Column 'added' cannot be null")
</code></pre>

blocks|key|56225|text|Model.objects.create()创建一个模型实例并保存它。Model()仅创建内存中的模型实例。直到您调用实例的save()方法来保存它，它才会保存到数据库中。这也是验证发生的时候。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|56226|entityMap^0|0|M|Z|7|1Q|6|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]|$9|M|A|N|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|O|8|@]|D|@]|E|$]]]|G|$]]

<code>Model.objects.create()</code> creates a model instance and saves it. <code>Model()</code> only creates an in memory model instance. It's not saved to the database until you call the instance's <code>save()</code> method to save it. That's when validation happens also.

What it the difference between running two commands:

<pre><code>foo = FooModel()
</code></pre>

and

<pre><code>bar = BarModel.objects.create()
</code></pre>

Does the second one immediately create a <code>BarModel</code> in the database, while for <code>FooModel</code>, the <code>save()</code> method has to be called explicitly to add it to the database?

Django Model() vs Model.objects.create()

数据库

Django

运行两个命令有什么区别：foo = FooModel()和bar = BarModel.objects.create()第二个方法是否立即在数据库中创建BarModel，而对于FooModel，必须显式调用save()方法才能将其添加到数据库中？

问Django Model() vs Model.objects.create()
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