I have a Many-to-Many relationship that I would like to keep track of the
order. I am wondering if I can automatically populate the module_position
field based on the current number of AgendaModule's for an Agenda.
class AgendaModule(db.Model):
__tablename__ = 'agenda_modules'
module_id = db.Column(db.Integer, db.ForeignKey('modules.id'),
primary_key=True)
agenda_id = db.Column(db.Integer, db.ForeignKey('agendas.id'),
primary_key=True)
module_position = db.Column(db.Integer)
# module_position = db.Column(db.Integer,
default=len(Agenda.query.get(agenda_id).modules) + 1) # NameError: name
'Agenda' is not defined
module = db.relationship('Module')
class Agenda(db.Model):
__tablename__ = 'agendas'
modules = db.relationship('AgendaModule', backref='agendas',
order_by=AgendaModule.module_position)
>>> a = Agenda(name='Test')>>> mod = Module.query.all()[0]>>> am =
>>> AgendaModule()>>> am.module = mod>>> am.module_position = len(a.modules) +
>>> 1>>> a.modules.append(am)>>> a.modules[<app.agendas.models.AgendaModule
>>> object at 0x7fe7ccfccd50>]>>> am.module_position1
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