在之前我們測試中,所有語句都在同一個檔案中,但隨著專案越來越大,管理起來有所不便,所以將Models分離.
基本的檔案結構如下

\—–app.py
\—–models.py

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from models import Article

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///./Article.db'
SQLALCHEMY_TRACK_MODIFICATIONS = False
 

db = SQLAlchemy(app)

# db.create_all()
@app.route('/')
def index():
    return 'index'

if __name__ == '__main__':
    #最好關閉debug
    app.run()

from app import db
class Article(db.Model):
    __tablename__='article'
    id = db.Column(db.Integer,primary_key=True)
    title = db.Column(db.String(100)
 
,nullable=False)
    content = db.Column(db.Text,nullable=False)

但此時會出現迴圈引用的錯誤,也就是你需要我的,我需要你的,錯誤如下圖

解決方法

新建一個exts.py檔案
\—–app.py
\—–models.py
\—–exts.py

exts.py檔案內容如下

from flask_sqlalchemy import SQLAlchemy
#此時先不傳入app
db = SQLAlchemy()

app.py更改如下
去掉from flask_sqlalchemy import SQLAlchemy
增加db.init_app(app)

from flask import Flask
from models import Article

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///./Article.db'
SQLALCHEMY_TRACK_MODIFICATIONS = False
db.init_app(app)

# db.create_all()
@app.route('/')
def index():
    return 'index'

if __name__ == '__main__':
    #最好關閉debug
    app.run()

models.py

from exts import db
class Article(db.Model):
    __tablename__='article'
    id = db.Column(db.Integer,primary_key=True)
    title = db.Column(db.String(100),nullable=False)
    content = db.Column(db.Text,nullable=False)