flask SQLAlchemy中一對多的關係實現

時間 2019-11-21

標籤 flask sqlalchemy 一對多的關係實現欄目 Python 简体版

原文原文鏈接

SQLAlchemy是Python中比較優秀的orm框架，在SQLAlchemy中定義了多種數據庫表的對應關係，html

其中一對可能是一種比較常見的關係。利用flask sqlalchemy實現一對多的關係以下：python

1. 創建數據庫的模型mysql

在本次試驗中創建三個表： user, phone ,atttr。user 和phone, phone 和atttr均爲一對多的關係。實現以下：sql

#!/usr/bin/env python
# -*- coding: utf-8 -*-

from flask import Flask
from flask.ext.sqlalchemy import SQLAlchemy

app = Flask(__name__)

# 配置數據庫
app.config[
    'SQLALCHEMY_DATABASE_URI'] = \
    "mysql://root: root@127.0.0.1/test?charset=utf8"
db = SQLAlchemy(app)

# 創建user表
class Usr(db.Model):
    __tablename__ = 'usr'
    id = db.Column(db.Integer, primary_key=True)
    usrname = db.Column(db.String(80), unique=True)
    email = db.Column(db.String(120), unique=True)
    phone = db.relationship('Phone', backref='user', lazy='dynamic')

    def __init__(self, username, email):
        self.usrname = username
        self.email = email

class Phone(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(20))
    factory = db.Column(db.String(20))
    userId = db.Column(db.Integer, db.ForeignKey('usr.id'))
    attr = db.relationship(
        'Atttr', backref='phone', lazy='dynamic')

    def __init__(self, name, factory, userId):
        self.name = name
        self.factory = factory
        self.userId = userId


class Atttr(db.Model):
    id = db .Column(db.Integer, primary_key=True)
    color = db.Column(db.String(20))
    price = db.Column(db.String(20))
    macId = db.Column(db.Integer, db.ForeignKey('phone.id'))

    def __init__(self, color, price, macId):
        self.color = color
        self.price = price
        self.macId = macId

db.create_all()

　　user表和phone表的一對多的關係經過下面語句肯定：數據庫

phone = db.relationship('Phone', backref='user', lazy='dynamic')

　　其中rrealtionship描述了user和phone的關係。在此文中，第一個參數爲對應參照的類"Phone";json

第二個參數backref爲類Phone申明新屬性的方法；第三個參數lazy決定了何時SQLALchemy從flask

數據庫中加載數據。api

2. 構造api獲取數據資源瀏覽器

　　注意：在獲取資源以前，先向數據庫中寫入測試數據restful

#!usr/bin/env pyhton
# -*- coding: utf-8 -*-

from flask import Flask
from flask.ext.restful import reqparse, Api, Resource
from model import *

app = Flask(__name__)
api = Api(app)


def to_json(model):
    """ Returns a JSON representation of an SQLAlchemy-backed object. """
    json = {}
    # json['fields'] = {}
    # json['pk'] = getattr(model, 'id')
    for col in model._sa_class_manager.mapper.mapped_table.columns:
        # json['fields'][col.name] = getattr(model, col.name)
        json[col.name] = getattr(model, col.name)
    # return dumps([json])
    return json


def to_json_list(model_list):
    json_list = []
    for model in model_list:
        json_list.append(to_json(model))
    return json_list


def message(record):
    if record:
        return to_json(record), 200
    return {"message": "not exit"}, 400


class userResource(Resource):

    def get(self, id):
        record = Usr.query.filter_by(id=id).first()
        return to_json_list(record.phone.first().phone)

    def put(self, id):
        parser = reqparse.RequestParser()
        parser.add_argument('username', type=str)
        args = parser.parse_args(strict=True)
        record = Usr.query.filter_by(id=id).first()
        if record:
            record.username = args['username']
            db.session.commit()
            return {"status": "updated"}, 201
        return {"message": "not exit"}, 400

    def delete(self, id):
        record = Usr.query.filter_by(id=id).first()
        if record:
            db.session.delete(record)
            db.session.commit()
            return {"status": "deleted"}, 204
        return {"message": "not exit"}, 400