Flask-Admin bir çok sayıya kadar sayılan alanı alandır

Question

Sahip ve Ekranlar arasında birden çok ilişkiye sahip olduğumuzu düşünelim (bir sahip birden çok ekrana sahip olabilir).

Her bir sahibin sahip olduğu ekran sayısını, bir hybrid_property kullanarak ve ilişkide count() yöntemini çağırarak gösteren bir sütun görüntülemek mümkündür. Ancak Web arayüzünde bu değer hesaplanan değer sıralanabilir yapmak için bir yol bulmak değil: Ben column_sortable_list içinde number_of_screens eklerseniz, aşağıdaki hata var: Burada

Traceback (most recent call last): 
    File "app.py", line 71, in <module> 
    admin.add_view(OwnerAdmin(Owner, db.session)) 
    File "C:\Python27\lib\site-packages\flask_admin\contrib\sqla\view.py", line 319, in __init__ 
    menu_icon_value=menu_icon_value) 
    File "C:\Python27\lib\site-packages\flask_admin\model\base.py", line 718, in __init__ 
    self._refresh_cache() 
    File "C:\Python27\lib\site-packages\flask_admin\model\base.py", line 795, in _refresh_cache 
    self._sortable_columns = self.get_sortable_columns() 
    File "C:\Python27\lib\site-packages\flask_admin\contrib\sqla\view.py", line 539, in get_sortable_columns 
    column, path = self._get_field_with_path(c) 
    File "C:\Python27\lib\site-packages\flask_admin\contrib\sqla\view.py", line 365, in _get_field_with_path 
    value = getattr(model, attribute) 
    File "C:\Python27\lib\site-packages\sqlalchemy\ext\hybrid.py", line 740, in __get__ 
    return self.expr(owner) 
    File "app.py", line 48, in number_of_screens 
    return self.screens.count() 
    File "C:\Python27\lib\site-packages\sqlalchemy\orm\attributes.py", line 193, in __getattr__ 
    key) 
AttributeError: Neither 'InstrumentedAttribute' object nor 'Comparator' object associated with Owner.screens has an attribute 'count' 

sorunu göstermek için bir örnek kod :

from flask import Flask 
from flask_sqlalchemy import SQLAlchemy 
from sqlalchemy.ext.hybrid import hybrid_property 

import flask_admin as admin 
from flask_admin.contrib import sqla 
from flask_admin.contrib.sqla.filters import IntGreaterFilter 

# Create application 
app = Flask(__name__) 

# Create dummy secrey key so we can use sessions 
app.config['SECRET_KEY'] = '123456790' 

# Create in-memory database 
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///sample_db_2.sqlite' 
app.config['SQLALCHEMY_ECHO'] = True 
db = SQLAlchemy(app) 


# Flask views 
@app.route('/') 
def index(): 
    return '<a href="/admin/">Click me to get to Admin!</a>' 


class Screen(db.Model): 
    __tablename__ = 'screen' 
    id = db.Column(db.Integer, primary_key=True) 
    width = db.Column(db.Integer, nullable=False) 
    height = db.Column(db.Integer, nullable=False) 
    owner_id = db.Column(db.Integer, db.ForeignKey('owner.id')) 
    owner = db.relationship('Owner', 
     backref=db.backref('screens', lazy='dynamic')) 

    @hybrid_property 
    def number_of_pixels(self): 
     return self.width * self.height 


class Owner(db.Model): 
    __tablename__ = 'owner' 
    id = db.Column(db.Integer, primary_key=True) 
    name = db.Column(db.Unicode) 

    @hybrid_property 
    def number_of_screens(self): 
     return self.screens.count() 


class ScreenAdmin(sqla.ModelView): 
    ''' Flask-admin can not automatically find a hybrid_property yet. You will 
     need to manually define the column in list_view/filters/sorting/etc.''' 
    list_columns = ['id', 'width', 'height', 'number_of_pixels'] 
    column_sortable_list = ['id', 'width', 'height', 'number_of_pixels'] 

    # make sure the type of your filter matches your hybrid_property 
    column_filters = [IntGreaterFilter(Screen.number_of_pixels, 
             'Number of Pixels')] 

class OwnerAdmin(sqla.ModelView): 
    ''' Flask-admin can not automatically find a hybrid_property yet. You will 
     need to manually define the column in list_view/filters/sorting/etc.''' 
    list_columns = ['id', 'name', 'number_of_screens'] 
    column_sortable_list = ['id', 'name', 'number_of_screens'] 


# Create admin 
admin = admin.Admin(app, name='Example: SQLAlchemy2', template_mode='bootstrap3') 
admin.add_view(ScreenAdmin(Screen, db.session)) 
admin.add_view(OwnerAdmin(Owner, db.session)) 

if __name__ == '__main__': 

    # Create DB 
    db.create_all() 

    # Start app 
    app.run(debug=True) 

Answer 1

Sen number_of_screens hibrit özellik için bir hybrid property expression değiştirici eklemeniz gerekir. Bu, belirli bir sahip için ekran sayısını hesaplamak için gerekli SQL'i yayan bir yöntemdir. Örneğin.

class Owner(db.Model): 
    __tablename__ = 'owner' 
    id = db.Column(db.Integer, primary_key=True) 
    name = db.Column(db.Unicode) 

    @hybrid_property 
    def number_of_screens(self): 
     return len(self.screens) 

    @number_of_screens.expression 
    def number_of_screens(cls): 
     return db.select([db.func.count(Screen.id)]).where(Screen.owner_id == cls.id).label("number_of_screens")