[Twisted-Python] How to chain deferred calls

[vitaly at synapticvision.com]

Very, very close to want I wanted to understand, thank you!

One more q please: what if I complicate the abc1() like following, is  
this expected to work or again I've missed the point?

   return (
          self.abc1().
          addErrback(self.handleFailure1).
          addCallback(self.abc2,args).
          addCallback(self.abc3).
          addErrback(self.handleFailure2)
     )

     def abc1(self):

         d = defer.Deferred()

         c = myClass()
         result = c.myTestFunc()
         if result != 1:
             d.addCallback(raiser)

         d.callback(result)
         return d

     def raiser(self, _):
         raise Exception("Error11")



Quoting "Terry Jones" <terry at jon.es>:

> If your code looked like this (pseudocode), you would see the exception
>
>     return (
>          self.abc1().
>          addErrback(self.handleFailure1).
>          addCallback(self.abc2,args).
>          addCallback(self.abc3).
>          addErrback(self.handleFailure2)
>     )
>
>     def abc1(self):
>         d = defer.Deferred()
>         d.addCallback(raiser)
>         d.callback(1)
>         return d
>
>     def raiser(self, _):
>         raise Exception("Error11")
>
> Because the thing that raises is being called by Twisted's deferred class,
> and its exception is caught and routed to d's errback chain and winds up in
> the handleFailure1 method.
>
> Does that make sense?
>
> Terry
>
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