Question

需要关于关系和过滤的一些帮助。鉴于以下模型，我如何通过Milestone.active_date对项目的里程碑进行排序？

尝试这个之后，我知道我不能用财产来做这件事。我已经尝试了，我得到的错误是它不是一个可映射的表是有道理的。那么，执行此操作的最佳/正确方法是什么？

我已经调查了hybrid_property并加入了但我似乎无法实现这一目标。我在数据库方面相当生疏，并且在使用ORM之前做过很多事情，所以非常感谢。

谢谢！

BW

class MilestoneType(db.Model):

    __tablename__ = 'MilestoneType'

    id = db.Column(db.Integer, primary_key=True, autoincrement=True)
    name = db.Column(db.String(25), nullable=False)
    icon_name = db.Column(db.String(255))

    def __repr__(self):
        return self.name


class Milestone(db.Model):

    __tablename__ = 'Milestone'

    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(50), nullable=False)
    milestone_type_id = db.Column(db.ForeignKey(MilestoneType.id))
    milestone_type = db.relationship("MilestoneType")
    milestone_dates = db.relationship("MilestoneDate", order_by="MilestoneDate.datestamp", lazy="dynamic")
    notes = db.Column(db.String(255), nullable=False)
    project_id = db.Column(db.Integer, db.ForeignKey('Project.id'), nullable=False)
    project = db.relationship("Project")

    @property
    def active_date(self):
        return self.milestone_dates.first()

    def __repr__(self):
        return str(self.name) + ' (Type: ' + str(self.milestone_type) + ')'


class MilestoneDate(db.Model):

    __tablename__ = 'MilestoneDate'

    id = db.Column(db.Integer, primary_key=True)
    milestone_id = db.Column(db.Integer, db.ForeignKey('Milestone.id'), nullable=False)
    milestone = db.relationship("Milestone")
    datestamp = db.Column(db.DateTime, nullable=False)
    notes = db.Column(db.String(255), nullable=False)

    def __repr__(self):
        return str(self.datestamp)


class Project(db.Model):

    __tablename__ = 'Project'

    id = db.Column(db.Integer, primary_key=True, autoincrement=True)
    active = db.Column(db.Boolean, nullable=False, default=True)
    name = db.Column(db.String(50), nullable=False)
    code = db.Column(db.String(8), nullable=False)
    responsible = db.Column(db.String(50), nullable=False)
    customer_id = db.Column(db.ForeignKey(Customer.id))
    customer = db.relationship("Customer")
    project_type_id = db.Column(db.ForeignKey(ProjectType.id))
    project_type = db.relationship("ProjectType")
    product_id = db.Column(db.ForeignKey(Product.id))
    product = db.relationship("Product")
    site_id = db.Column(db.ForeignKey(Site.id))
    site = db.relationship("Site")
    milestones = db.relationship("Milestone", lazy="dynamic")

    def __repr__(self):
        return str(self.customer) + " - " + str(self.name) + '(' + str(self.product) + ')'

SqlAlchemy按关系列

0 个答案: