Flask – Flask-Admin – One-To-Many – Cascade

Issue

I’m currently starting a project with Flask. I’m currently experiencing Flask-Admin.

I try to setup a 2 levels relationship. For each “Candidat” I like to associate a language and a level (LanguageLevel) for this language.

Here is my models.py

from app import db

class Candidat(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    firstname = db.Column(db.String(128))
    lastname = db.Column(db.String(128))
    birthdate = db.Column(db.DateTime)
    languages = db.relationship("CandidatLanguage", backref="candidat")

    def __repr__(self):
        return '<Nom %r>' % self.lastname


class Language(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(128))

    def __repr__(self):
        return '<Langues %r>' % self.name

class Languagelevel(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(128))

    def __repr__(self):
        return '<Niveau : %r>' % self.name

class CandidatLanguage(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    candidat_id = db.Column(db.Integer, db.ForeignKey('candidat.id'))
    language_id = db.Column(db.Integer, db.ForeignKey('language.id'))
    langguage_level_id = db.Column(db.Integer, db.ForeignKey('languagelevel.id'))

Here is my views.py

from models import Candidat, Languagelevel, Language, CandidatLanguage

from flask.ext.admin import Admin, BaseView, expose
class MyView(BaseView):
    @expose('/')
    def index(self):
        return self.render('adm-index.html')

admin = Admin(app)
admin.add_view(MyView(name='Hello'))

from flask.ext.admin.contrib.sqla import ModelView

admin.add_view(ModelView(Candidat, db.session))
admin.add_view(ModelView(CandidatLanguage, db.session))
admin.add_view(ModelView(Language, db.session))
admin.add_view(ModelView(Languagelevel, db.session))

What I would like to have is a Candidat form wich looks like this:

Firstname : ____

Lastname : _____

Language :

  • DropDown for Language :

    • Language 1
    • Language 2
  • DropDown for LanguageLevel :

    • Level 1
    • Level 2

For one “Candidat”, one Language can only be associated with one LanguageLevel.

I’ve tried column_auto_select_related, column_display_all_relations, and of course none of them works like I thought. Of course this is my mistake.

If someone can show me the right way for reaching my goal it would be really helpfull.

Thanks in advance.

Regards

Solution

Finally, I’ve found my solution in the following post

My mistakes were:

  • putting a db.relationship (CandidatLanguage) in my Candidat
    class. Instead of that, I put relations in my “pivot” table
    (CandidatLanguage).
  • as IfLoop said in the post, I have to “switch from a plain
    many-to-many relationship to an “Association Object”. I don”
    understood why but it works using Association object.

Then my models.py now looks like this:

class Candidat(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    firstname = db.Column(db.String(128))
    lastname = db.Column(db.String(128))
    birthdate = db.Column(db.Date)
    categories = db.relationship('Category', secondary=category_candidat,
                                 backref=db.backref('candidat', lazy='dynamic'))

    def __repr__(self):
        return '<Nom %r>' % self.lastname


class Language(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(128))

    def __repr__(self):
        return '%s' % unicode(self.name)


class Languagelevel(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(128))

    def __repr__(self):
        return '%s' % self.name

class CandidatLanguage(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    candidat_id = db.Column(db.Integer, db.ForeignKey('candidat.id'))
    language_id = db.Column(db.Integer, db.ForeignKey('language.id'))
    language_level_id = db.Column(db.Integer, db.ForeignKey('languagelevel.id'))

    language = db.relationship(Language, backref="Candidat")
    candidat = db.relationship(Candidat, backref="Langue")
    languagelevel = db.relationship(Languagelevel, backref="Candidat")

And my views.py like that:

from flask.ext.admin import Admin, BaseView, expose
class MyView(BaseView):
    @expose('/')
    def index(self):
        return self.render('adm-index.html')

admin = Admin(app)
admin.add_view(MyView(name='Hello'))

from flask.ext.admin.contrib.sqla import ModelView

class CandidatView(ModelView):
    column_auto_select_related = True
    inline_models = (CandidatLanguage,)

admin.add_view(CandidatView(Candidat, db.session))
admin.add_view(ModelView(Language, db.session))
admin.add_view(ModelView(Languagelevel, db.session))

With that, everything works fine and I have an inline form like I want.

I haven’t understood everything but it works. if somebody can explain, it’s of coruse welcome.

Regards

Answered By – Youpsla

This Answer collected from stackoverflow, is licensed under cc by-sa 2.5 , cc by-sa 3.0 and cc by-sa 4.0

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