sqlalchemy - 与 wtforms_alchemy.ModelFieldList 的一对多关系不更新子级

Question

下面是一个填充空父对象并创建其子对象的表单。必须手动调用 ModelFormField，这是一个小麻烦。它工作得很好。但是，当我使用表单进行更新时，只有对象被更新——子对象是新创建的。

在这个框架中向孩子传播更新的正确方法是什么？实际上，我想使用下面的两个打印语句来打印相同的内容。如果表单数据有额外的（丢失的）孩子数据，如果表单会创建（删除）孩子，我将特别感激。

from multidict import MultiDict
from sqlalchemy import Column, ForeignKey, Integer, String
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import relationship
from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine

from wtforms_alchemy import ModelFieldList, ModelForm, ModelFormField

Base = declarative_base()

class Child(Base):
  __tablename__ = "child"
  id = Column(Integer, primary_key=True)
  name = Column(String)
  parent_id = Column(Integer, ForeignKey("parent.id"))

class Parent(Base):
  __tablename__ = "parent"
  id = Column(Integer, primary_key=True)
  name = Column(String)
  children = relationship(Child)

class ChildForm(ModelForm):
  class Meta:
    model = Child

class ParentForm(ModelForm):
  class Meta:
    model = Parent
  children = ModelFieldList(ModelFormField(ChildForm))  # annoyed!

engine = create_engine("sqlite://")
Base.metadata.create_all(engine)
Session = sessionmaker(bind=engine)
session = Session()

# Form data
formdata = MultiDict({"name": "Foo", "children-0-name": "hotdog"})

# Create initial object
question = Parent()
form = ParentForm(formdata, obj=question)
form.populate_obj(question)
if not form.validate():
  raise RuntimeError(form.errors)
session.add(question)
session.commit()

# prints: "(1, 1)"
print((question.id, question.children[0].id))


# Retrieve object and update with same data
question_get = session.query(Parent).get(question.id)
form = ParentForm(formdata, obj=question_get)
form.populate_obj(question_get)
if not form.validate():
  raise RuntimeError(form.errors)
session.add(question_get)
session.commit()

# prints: "(1, 2)", want it to print the same as above
print((question_get.id, question_get.children[0].id))

标签： sqlalchemywtforms

Answer 1

在深入研究代码时，看起来需要更新对象 ID。因此，必须在更新时使用包含 id 并传递 id 的表单。

--- orig.py 2018-05-01 20:51:09.000000000 -0700
+++ fixed.py    2018-05-01 20:56:16.000000000 -0700
@@ -4,6 +4,7 @@
 from sqlalchemy.orm import relationship
 from sqlalchemy.orm import sessionmaker
 from sqlalchemy import create_engine
+from wtforms import IntegerField

 from wtforms_alchemy import ModelFieldList, ModelForm, ModelFormField

@@ -24,6 +25,7 @@
 class ChildForm(ModelForm):
   class Meta:
     model = Child
+  id = IntegerField()  # Optional field used in update operations.

 class ParentForm(ModelForm):
   class Meta:
@@ -53,7 +55,11 @@

 # Retrieve object and update with same data
 question_get = session.query(Parent).get(question.id)
-form = ParentForm(formdata, obj=question_get)
+child_id = question_get.children[0].id
+formdata_update = MultiDict({"name": "Foo",
+                             "children-0-id": child_id,
+                             "children-0-name": "pizza"})
+form = ParentForm(formdata_update, obj=question_get)
 form.populate_obj(question_get)
 if not form.validate():
   raise RuntimeError(form.errors)