Question

我正在尝试使用sqlalchemy-imageattach将图像附加到db.Model，并使用flask / jinja2在模板中呈现它们。只要实际附加了图像，这一切都可以正常工作。如果该字段为空，则抛出异常（OSError：还没有原始图像）。如何避免空字段上的异常或为jinja2模板添加一些异常处理？谢谢！

foreach($groups as $group) { echo $group->user_count }：

app.py

from flask import Flask, render_template from flask_sqlalchemy import SQLAlchemy from sqlalchemy_imageattach.stores.fs import HttpExposedFileSystemStore from sqlalchemy_imageattach.context import (pop_store_context, push_store_context) from sqlalchemy_imageattach.entity import Image, image_attachment app = Flask(__name__) db = SQLAlchemy(app) app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///:memory:' store = HttpExposedFileSystemStore( path='images', prefix='static/images/' ) app.wsgi_app = store.wsgi_middleware(app.wsgi_app) class Person(db.Model): __tablename__ = 'person' id = db.Column(db.Integer, primary_key=True) name = db.Column(db.String, nullable=False) image = image_attachment('PersonImage') def __init__(self, name): self.name = name class PersonImage(Image, db.Model): __tablename__ = 'person_image' person_id = db.Column( db.Integer, db.ForeignKey('person.id'), primary_key=True) person = db.relationship('Person') @app.before_request def start_implicit_store_context(): push_store_context(store) @app.teardown_request def stop_implicit_store_context(exception=None): pop_store_context() @app.route('/') def index(): person = Person(name='Hello') # with open('test.jpg', 'rb') as f: # person.image.from_file(f) db.session.add(person) db.session.commit() return render_template('index.html', person=person) if __name__ == '__main__': db.create_all() app.run(debug=True)：

index.html

Answer 1

尝试在index.html中更改您的代码，如下所示：

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title></title>
  </head>
  <body>
    {{ person.name }}
    {% if person.image is not none %}
       {{ person.image }} 
    {% else %}
       <img src="default.png">
    {% endif %}
  </body>
</html>

Answer 2

简单使用if条件。

<html>
  <head>
    <meta charset="utf-8">
    <title></title>
  </head>
  <body>
    {{ person.name }}
    {{ person.image if person.image}}
  </body>
</html>

Answer 3

好的，回答我自己的问题：您必须在模板中使用{{ person.image.original }}或检查if person.image.count()。 sqlalchemy-imageattach documentation只是提到{{ person.image }}扩展为<img src="{{ user.picture.locate() }}" width="{{ user.picture.width }}" height="{{ user.picture.height }}">。这对于空图像字段不起作用，并且在使用明显的解决方案来检查{% if person.image %}时也不起作用，因为sqlalchemy-imageattach在空图像字段上不返回None但总是抛出异常。相关代码为here：

image = self.original
if not image:
    raise IOError('there is no original image yet')
return image

如何渲染使用SQLAlchemy-imageattach创建的空图像字段没有＆＃34; OSError：还没有原始图像＆＃34;例外

3 个答案: