[Flask] Should extension use an app instance if it's passed to constructor or just always use flask.current_app?

[Andrew Pashkin]

Hello, everybody!

I'm reading about extensions development 
<http://flask.pocoo.org/docs/0.10/extensiondev/> and it says:

    As you noticed, |init_app| does not assign |app| to |self|. This is
    intentional! *Class based Flask extensions must only store the
    application on the object when the application was passed to the
    constructor.* This tells the extension: I am not interested in using
    multiple applications.

    *When the extension needs to find the current application and it
    does not have a reference to it, it must either use the
    **|current_app|
    <http://flask.pocoo.org/docs/0.10/api/#flask.current_app>* context
    local or change the API in a way that you can pass the application
    explicitly.

But the example extension 
<http://flask.pocoo.org/docs/0.10/extensiondev/#the-extension-code>, 
just uses flask.current_app, without checking whether an application 
instance was attached to the extension instance:

    ... def  connect(self):
         return  sqlite3.connect(*current_app*.config['SQLITE3_DATABASE'])
    ...

So, where is the truth? What extension should really do - always use 
flask.current_app, or use it only if application instance wasn't passed 
to the constructor?

-- 
With kind regards, Andrew Pashkin.
cell phone - +7 (985) 898 57 59
Skype - waves_in_fluids
e-mail - andrew.pashkin at gmx.co.uk

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