基于扭曲延迟的Python面向对象设计

Question

我的问题是如何设计与面向对象设计和异步延迟(而不是阻塞代码)很好地协同工作的代码。

好的，我在考虑设计这个类的两种方式(这些是好的设计，还是我忘了什么)

第一种方法

class Grooveshark(object):
def get_session(self):
    d = # implementation detail (gets page)
    d.addCallback(self.parse_session)# implmentation detail
    # all in all this goes through and sets self.session to the session value (it does not return it though; should I set it and return it?)
    self.session_time = time.time()
    return d
def get_country_id(self):
    # implmentation acts same as d just parses to diferrent id
    # also it grabs the same page; ANNOYING having to get the page twice ugh

def get_token(self):
    # relies on self.session being set
    d = # implmentation detail
    d.addCallback(self.parse_token)# implmentation detail
    # at the end of the day it sets self.token and then fires the deferred (same as session does not send it through the deferred, again should I seem repetitive?)
    return d
def construct_api_call(method, url, implmentation_arguments...)
    # checks if session is hour old
    if self.session_time - 3600 <= time.time() or self.session is None:

        # update
        d = get_session()
        # some how pass deferred or something
        d.addCallback(lambda ignored: self.get_country_id)
        d.addCallback(lambda ignored: self.get_token())
        d.addCallback(lambda ignored: self.construct_api_call(method, url, implmentation_arguments)
        # if error retry
        d.addErrback(lambda error: log.err(error))
        d.addErrback(lambda ignored: self.construct_api_call(method, url, implmentation_arguments)
        return d# would this work?  problem: with this how do I get it so I can do this whole update and do this again with the deferred I returned

    else:
        #implmentation details
        return d# fires when done with api call

第二种方式

class Grooveshark(object):
def get_session(self):

    d = # implmentation detail
    # differance this sends the session down the deferred callback and sets the instance var self.session (seems strange both modifying state and returning)

def get_token(self, session):
    d = # gets token but uses session argument NOT intance variable

def get_country_id # same as first class 

def construct_api_call(session, session_time, token, country_id, all the other args in above class):
    # problems it requires user of api to store session etc also how do I return if needs update right now I just error
    if self.session_time - 3600 <= time.time():
        raise RuntimeError("You need to update your session, ugh why does the user have to store the session ugh")

    else:
        # does what above class does as well

Answer 1

简短的回答:请参阅@defer.inlineCallbacks

不管是函数式编程还是面向对象编程，使用Twisted的关键和好处在于，它使用回调事件驱动设计来允许异步程序执行。一个常见的观察是，事件驱动编程需要改变编码风格和布局-正如您的问题所指出的那样。

在几乎所有情况下，在方法或函数中使用"@defer.inlineCallbacks“修饰器将有助于使扭曲的代码模块化和可重用。当您使用这种方法编写源代码时，您可以编写不会在这么多函数之间“分割”的异步代码。每当你的代码块需要转到下一个阻塞或“延迟”段时，它都会使用yield命令。这允许函数在延迟完成时从它停止的地方继续。这使得回调链看起来像是常规的阻塞代码。

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