如何使用字符串表示sqlalchemy对象属性? [英] how can i use a string to to represent an sqlalchemy object attribute?

问题描述

我正在用SQLalchemy和WTForms编写Flask应用程序.

I am writing a Flask application with SQLalchemy and WTForms.

数据库更新遇到问题...我有很多对象表字段正在尝试更新.

Trouble with database updates... I have many object table fields I am trying to update.

所以我从这里开始...

so I started with this...

# this works great but needs many lines of code
event.evt_num = form.evt_num.data
event.evt_name = form.evt_name.data
event.evt_location = form.evt_location.data
event.evt_address = form.evt_address.data
event.evt_city = form.evt_city.data
event.evt_state = form.evt_state.data
...

尽管上面的代码片段有效，但实际上它是巨大的.因此，我想变得更聪明，并遍历属性以更新数据库.所以我尝试了以下...

While the above snippet works, in reality it is huge. So I would like to be smarter and iterate thru the attributes to update the database. So I tried the following...

event_fields = ('evt_num', 'evt_name', 'evt_location', 'evt_address',
                    'evt_city', 'evt_state', 'evt_zip', 'evt_notes')

for aa in event_fields:
    print "form data", getattr(form, aa).data  # prints posted form data
    print "db data", getattr(event, aa) # prints posted data from database

    if getattr(form, aa).data != getattr(event, aa):  # if form data shows a change
        setattr(event, aa, getattr(form, aa).data)    # update database does not work
        db_change = True
        session.flush()
        ...

此行不适用于更新数据库:

This line doesnt work to update the database:

setattr(event, aa, getattr(form, aa).data)

我收到此错误" AttributeError:'事件'对象没有属性'aa'"

我们将非常感谢您的帮助.

Your help will be greatly appreciated.

推荐答案

如果您像这样进行重组怎么办?

What if you restructured like this?

event_fields = ('evt_num', 'evt_name', 'evt_location', 'evt_address',
            'evt_city', 'evt_state', 'evt_zip', 'evt_notes')

for aa in event_fields:
    form_data = getattr(form, aa).data
    db_data = getattr(event,aa)
    print "form data", form_data  # prints posted form data
    print "db data", db_data # prints posted data from database

    if form_data != db_data:  # if form data shows a change
        setattr(event, aa, form_data)    # update database now works
        db_change = True
        session.flush()
        ...

这样，您对getattr()的调用减少了，并且可能会稍微优化代码.

This way, you make fewer calls to getattr() and maybe optimize your code slightly.

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