[Tutor] Class decorator on a derived class not initialising the base classes using super - TypeError

[Sangeeth Saravanaraj]

Peter, Spir - thanks for your time and effort!

I am posting this query to few more Python mailers.

Thank you,

Sangeeth


On Tue, Feb 25, 2014 at 5:22 AM, spir <denis.spir at gmail.com> wrote:

> On 02/24/2014 08:19 PM, Sangeeth Saravanaraj wrote:
>
>> Sorry, I should have described what I was trying!
>>
>> I want to create a decorator which should do the following things:
>>
>>     - When an object of the decorated class is created, the objects name
>>
>>     (say the value of the incoming "id" argument) should be stored as a
>> record
>>     in a table in a database.
>>     - When an object of the decorated class is deleted, the record with
>> this
>>
>>     deleted objects name (i.e. object.id) should be removed from the
>> table.
>>
>> You can safely assume that all the database operations are working fine!
>>
>> Now, for example - consider the following snippet:
>>
>> @saveme
>> class A(object):
>>      def __init__(self, id):
>>          self.id = id
>>
>> @saveme
>> class B(object):
>>      def __init__(self, id):
>>          self.id = id
>>
>> "saveme" should do what I have explained earlier.
>>
>> a1 = A("A1")
>> a2 = A("A2")
>> a3 = A("A3")
>> b1 = B("B1")
>> b2 = B("B2")
>>
>> At this point if I query and print all the records in a table, I should
>> get
>> the following:
>> output: ["A1", "A2", "A3", "B1", "B2"]
>>
>> del a1
>> del a2
>> del a3
>> del b1
>> del b2
>>
>> At this point, all entries in the table should be deleted; query should
>> return an empty list!
>>
>> And, I want to highlight that the classes that are being decorated with
>> "saveme" can de derived classes too!
>>
>> What is the best way to do this?!
>>
>> Thank you,
>>
>> Sangeeth
>>
>
> Your problem looks like a typical "crosscutting" (transversal) concern
> addressed by AOP (Aspect Oriented Programming). Their usual example is in
> fact logging. Look at the wikipedia page:
> https://en.wikipedia.org/wiki/Aspect-oriented_programming
>
> Not that it would help you solve it _in python_, but this may serve at
> least to better understand what kind of problem you are actually facing;
> and why it is annoying in programming (with common languages); what may be
> your options.
>
> [I have no better approach than yours, using magic metamethods, and a
> decorator to wrap it all.]
>
>
> d
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