config.py 文件源码

def configure_db(app):
    from sqlalchemy import event
    from sqlalchemy.orm import mapper
    from sqlalchemy.inspection import inspect

    alembic.init_app(app)
    db.init_app(app)
    nplusone.init_app(app)

    @event.listens_for(mapper, "init")
    def instant_defaults_listener(target, args, kwargs):
        for key, column in inspect(type(target)).columns.items():
            if column.default is not None:
                if callable(column.default.arg):
                    setattr(target, key, column.default.arg(target))
                else:
                    setattr(target, key, column.default.arg)

    event.listen(mapper, 'init', instant_defaults_listener)