Switching between cmd.CMD instances

Wed Apr 2 19:33:07 EDT 2014

On Wed, Apr 2, 2014 at 1:03 AM, Josh English <Joshua.R.English at gmail.com>wrote:
> I have a program with several cmd.Cmd instances. I am trying to figure out
> what the best way to organize them should be.
>> I've got my BossCmd, SubmissionCmd, and StoryCmd objects.
>> The BossCmd object can start either of the other two, and this module
> allows the user switch back and forth between them. Exiting either of the
> sub-command objects returns back to the BossCmd.
>> I have defined both a do_done and do_exit method on the sub-commands.
>> Is it possible to flag BossCmd so when either of the other two process
> do_exit, the BossCmd will also exit?
>
I have an app that also has a number of cmd.Cmd subclasses to implement
different interpreter layers. I haven't needed to implement what you're
talking about here (exiting one interpreter just drops you down to a
lower-level interpreter). However, it's definitely possible. You can have
your SubmissionCmd and StoryCmd take a "master" (BossCmd) object in its
__init__ method and store the BossCmd as an instance attribute.
>From there, you can implement a method interface in which the child Cmd
subclasses can call to indicate to BossCmd that do_exit has been called and
it should quit after the child's cmdloop returns. So something like this:
class SubmissionCmd(cmd.Cmd):
 # your stuff
 def __init__(self, master):
 cmd.Cmd.__init__(self, *your_args)
 self.master = master
 def do_exit(self, line):
 self.master.child_has_exited()
class BossCmd(cmd.Cmd):
 # your stuff
 def child_has_exited(self):
 self.exit_on_return = True # this should be set False in __init__
 def do_submit(self, line):
 subcmd = SubmissionCmd(self)
 subcmd.cmdloop()
 if self.exit_on_return: return True
Untested and incomplete, but you get the idea.
HTH,
Jason
-- 
Jason M. Swails
BioMaPS,
Rutgers University
Postdoctoral Researcher
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