Hey Tony,
Thanks, that makes sense.
Part of me feels that it might be a bit heavy-handed to pickle, as the
commands are little more than a name and an argument, arguments being
plain-old-data in this case. Something I think could potentially be
enforced if I continue down this path.
A data-interchange format or protocol sounds reasonable and something I’ll
look into. You’re thinking in terms of a pre-defined dictionary via
something like JSON?
{
'command': 'create',
'args': ['age', 5]
}
Best,
Marcus
On 16 May 2014 15:08, Tony Barbieri <[email protected]> wrote:
> You could also use json or another data-interchange format and write a
> simple serializer to reinstantiate your python objects. Or abstract it to
> support multiple serialization backends.
>
>
> On Fri, May 16, 2014 at 10:07 AM, Tony Barbieri <[email protected]>wrote:
>
>> If you do decide to use python objects you could use pickling as long as
>> you only plan on reusing the history in python.
>>
>>
>> On Fri, May 16, 2014 at 10:02 AM, Marcus Ottosson <[email protected]
>> > wrote:
>>
>>> Hey guys,
>>>
>>> Does anyone have experience using the command
>>> pattern<http://en.wikipedia.org/wiki/Command_pattern>?
>>> I’m looking for a few things that this pattern seems to help with.
>>>
>>> -
>>>
>>> Undo/redo (preferable multi-level and persistent)
>>> -
>>>
>>> Action logging (what the user has done, in which order, and where
>>> things went wrong using which arguments)
>>> - Distribution of commands via a network (serialisation,
>>> asynchronous execution)
>>>
>>> I took a whack at it and found it rather straightforward to make a
>>> scripting-language out of it.
>>>
>>> The Command Pattern<https://gist.github.com/mottosso/f5722c4afd1b0791c4d3>
>>>
>>> There’s an example run at the bottom, but the ‘gist’ of it is this:
>>>
>>> ______________________________________________________
>>> | |
>>> | Command Pattern - Demonstration |
>>> | Author: Marcus Ottosson <[email protected]> |
>>> |______________________________________________________|
>>>
>>> * Available commands
>>> cls
>>> create
>>> data
>>> delete
>>> exit
>>> help
>>> history
>>> redo
>>> undo
>>> update
>>> verbosity
>>>
>>> command> create key value
>>> command> create age 5
>>> command> create length 1.57
>>> command> data
>>> age=5
>>> length=1.57
>>> key=value
>>>
>>> command> undo
>>> command> redo
>>> command> help update
>>> Update existing value in DATASTORE
>>>
>>> Args:
>>> key: Identifier for value
>>> value: Value for identifier
>>>
>>> Precondition:
>>> `key` must already exist
>>>
>>> Example:
>>> command> update age 5
>>>
>>> The main questions are about two aspects of it’s design:
>>>
>>> *History is stored as class attributes*
>>>
>>> Which means that commands add themselves to history, which wouldn’t work
>>> too great if they are accessed from separate threads.
>>>
>>> *History is stored as Python objects, as opposed to simple strings*
>>>
>>> Which means that history would be tricky to serialise and persist on
>>> disk or across a network.
>>>
>>> Thoughts?
>>>
>>> Best,
>>> Marcus
>>> --
>>> *Marcus Ottosson*
>>> [email protected]
>>>
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>>
>>
>>
>> --
>> -tony
>>
>
>
>
> --
> -tony
>
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--
*Marcus Ottosson*
[email protected]
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