模型中的外键模型__repr __（）

Question

我的Flask应用程序中有一个Artist-hasMany-Suggestion关系（用Flask-SQLAlchemy实现）。

我的艺术家课程如下：

class Artist(db.Model):
    __tablename__ = 'artists'

    suggestions = db.relationship('Suggestion', backref='artist')

我的Suggestion类看起来像：

class Suggestion(db.Model):
    __tablename__ = 'suggestions'

    id = db.Column(db.Integer, primary_key=True, autoincrement=True)
    artist_id = db.Column(db.Integer, db.ForeignKey('artists.id'))

    def __repr__(self):
        return '<Suggestion %r>' % (self.artist.name,)

显然，问题是没有为Suggestion模型定义self.artist。我能做些什么来实现这个目标？

Answer 1

Actualy问题是Suggestion不一定有关联Artist。它打破了一切。因此，请检查self.artist None或强制它NULL。

我的测试代码：

class Artist(db.Model):
    __tablename__ = 'artists'

    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(80))
    suggestions = db.relationship('Suggestion', backref='artist')

class Suggestion(db.Model):
    __tablename__ = 'suggestions'

    id = db.Column(db.Integer, primary_key=True, autoincrement=True)
    artist_id = db.Column(db.Integer, db.ForeignKey('artists.id'))

    def __repr__(self):
        return '<Suggestion %r>' % (self.artist.name,)

和IPython会议：

In [1]: from sqlalch import db, Artist, Suggestion

In [2]: Artist.query.all()
Out[2]: [<sqlalch.Artist at 0x3559490>]

In [3]: Suggestion.query.all()
Out[3]: [<Suggestion u'Hey You!'>]

In [4]: Suggestion.query.all()[0].artist
Out[4]: <sqlalch.Artist at 0x3559490>