遵从DRY原则，在定义model的时候，我尽量使用继承的方法去定义一些类似的model，但是碰到一个问题，就是model里的fields位置好像不受控制，比如继承类的field总是排在基类的后面
下面例子：在继承类DormEvaluationItemCriteriaTest里面添加一个新的新的field: check_date，执行migration之后，这个变量总是排在最后
class AbstractMonthlySafetyCheckItemCriteriaCategory(models.Model):
category = models.CharField(_("category"), max_length=30, blank=False, null=False)
class Meta:
abstract = True
class DormEvaluationItemCriteriaTest(AbstractMonthlySafetyCheckItemCriteriaCategory):
check_date = models.DateField(_('Check Date'),auto_now_add=True, auto_now=False)
class Meta:
abstract = False
class Migration(migrations.Migration):
dependencies = [
('monthlyinspection', '0024_auto_20180219_0028'),
]
operations = [
migrations.CreateModel(
name='DormEvaluationItemCriteriaTest',
fields=[
('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
('category', models.CharField(max_length=30, verbose_name='category')),
('check_date', models.DateField(auto_now_add=True, verbose_name='Check Date')),
],
options={
'abstract': False,
},
),
]
后来我试了一下把所有的field都定义在虚基类里面，但是field的排序并不跟基类的位置有关，而且由基类在model文件的定义顺序决定的，
比如定义了一下三个虚基类
class AbstractMonthlySafetyCheckItemCriteriaCategory(models.Model):
category = models.CharField(_("category"), max_length=30, blank=False, null=False)
class Meta:
abstract = True
class AbstractMonthlySafetyCheckItemCriteria(models.Model):
index = models.CharField(_("index"), max_length=30, blank=False, null=False, unique=True)
check_item = models.CharField(_('check item'), max_length=130, blank=False, null=False)
check_criteria = models.TextField(_('check criteria'), max_length=500, blank=False, null=False)
class Meta:
abstract = True
class AbstractMonthlySafetyCheckItemCriteriaScore(models.Model):
score_criteria = models.TextField(_('score criteria'), max_length=500, blank=True, null=True)
score_reference = models.CharField(_('score reference'), max_length=30, blank=True, null=True)
comments = models.TextField(_('comments'), max_length=500, blank=True, null=True)
class Meta:
abstract = True
那么，当我定义如下的继承类时，不管三个基类的排放顺序如何，migrations之后生成的field的位置都是固定的
class DormEvaluationItemCriteriaTest(
AbstractMonthlySafetyCheckItemCriteriaCategory,
AbstractMonthlySafetyCheckItemCriteria,
AbstractMonthlySafetyCheckItemCriteriaScore
):
class Meta:
abstract = False
或者
class DormEvaluationItemCriteriaTest(
AbstractMonthlySafetyCheckItemCriteria,
AbstractMonthlySafetyCheckItemCriteriaScore,
AbstractMonthlySafetyCheckItemCriteriaCategory
):
Field的顺序跟class的定义是一致的
class Migration(migrations.Migration):
dependencies = [
('monthlyinspection', '0024_auto_20180219_0028'),
]
operations = [
migrations.CreateModel(
name='DormEvaluationItemCriteriaTest',
fields=[
('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
('category', models.CharField(max_length=30, verbose_name='category')),
('index', models.CharField(max_length=30, unique=True, verbose_name='index')),
('check_item', models.CharField(max_length=130, verbose_name='check item')),
('check_criteria', models.TextField(max_length=500, verbose_name='check criteria')),
('score_criteria', models.TextField(blank=True, max_length=500, null=True, verbose_name='score criteria')),
('score_reference', models.CharField(blank=True, max_length=30, null=True, verbose_name='score reference')),
('comments', models.TextField(blank=True, max_length=500, null=True, verbose_name='comments')),
],
options={
'abstract': False,
},
),
]
有什么办法可以手动的调整field的顺序吗？
Django model 不允许域覆盖
https://docs.djangoproject.com/en/2.0/topics/db/models/#field-name-hiding-is-not-permitted
参考https://stackoverflow.com/questions/19025586/django-model-inheritance-overriding-fields
In normal Python class inheritance, it is permissible for a child class to override any attribute from the parent class. In Django, this is not permitted for attributes that are Field instances (at least, not at the moment). If a base class has a field called author, you cannot create another model field called author in any class that inherits from that base class.