On May 12, 2009, at 10:47 AM, Phil Christensen wrote:
I don't know if I agree with the need for such a feature (that is,
deferred __init__ usage), but it was a very interesting coding
challenge I wanted to take a whack at. I *think* I might have found a
solution, but I don't know if it falls under the heading of "decorator
abuse" ;-)
Ugh, that code got fairly mangled by my email client. Here's an
attachment.
-phil
from twisted.internet import defer, reactor
from twisted.enterprise import adbapi
def deferredInit(func):
if not(hasattr(deferredInit, 'waiting')):
deferredInit.waiting = {}
def _deferredInit(self, *args, **kwargs):
waiting_for_init = self in deferredInit.waiting
if not(waiting_for_init):
if(hasattr(self, 'initDeferred')):
deferredInit.waiting[self] = self.initDeferred
else:
raise RuntimeError("%s doesn't seem to support deferred instantion." % self.__class__.__name__)
def _finish(result):
del deferredInit.waiting[self]
return func(self, *args, **kwargs)
def _finish_error(failure):
print '_finish_err: %s' % failure
resultDeferred = defer.Deferred()
resultDeferred.addCallbacks(_finish, _finish_error)
deferredInit.waiting[self].addCallbacks(resultDeferred.callback, resultDeferred.errback)
return resultDeferred
return _deferredInit
class TestDeferredInit(object):
def __init__(self):
self.pool = adbapi.ConnectionPool("MySQLdb", 'localhost', 'modu', 'modu')
self.initDeferred = self.pool.runQuery("SELECT 'it worked';")
def _finish_init(msg):
self.msg = msg
def _finish_init_error(failure):
print '_finish_init_err: %s' % failure
self.initDeferred.addCallbacks(_finish_init, _finish_init_error)
@deferredInit
def query(self):
return self.msg
if(__name__ == '__main__'):
def _print(msg):
print msg
reactor.stop()
def _print_error(failure):
print '_print_err: %s' % failure
test = TestDeferredInit()
d = test.query()
d.addCallbacks(_print, _print_error)
reactor.run()
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