Thank you for your answer.
I'm sorry, I have not been clear enough regarding the "__abstract__ = True".
I suppose that I will have to add this to a lot of classes for the
following reasons :
1) because it will allow me to persist the classes one by one and still be
able to run and test the project (i will not have all the errors because
there is no table name and no primary key). So, I would have to delete the
"__abstract__" when I begin to work on the persistence of a new class.
2) because I thought that the best solution in this case is to map only the
concrete classes. So, in my example, I would have to map "Player" and
"NPC", but not "Character". So only the classes at the bottom of the
hierarchy would have to be mapped. That's still a lot of classes but
probably easier to implement.
But I have to say that this is not absolutely clear for me for now. This is
the first time I use SQLAlchemy. Do you think that this method is possible
and is the right way to proceed ?
Le vendredi 20 octobre 2017 20:02:40 UTC+2, Mike Bayer a écrit :
>
>
> CONTINUING ! sorry
>
>
> On Fri, Oct 20, 2017 at 11:55 AM, Sven Dumay <sven....@gmail.com
> <javascript:>> wrote:
>
>>
>> *I tried other things and I found the following solution :*
>>
>> from sqlalchemy.ext.declarative import declarative_base, DeclarativeMeta
>> from sqlalchemy import Column, Integer
>>
>> class MetaBase(DeclarativeMeta):
>>
>> def __init__(cls, nom, bases, contenu):
>> super(MetaBase, cls).__init__(nom, bases, contenu)
>> print("Init MetaBase")
>>
>> Base = declarative_base(metaclass = MetaBase)
>>
>> class Stockable(Base):
>>
>> __abstract__ = True
>>
>> def __init__(self):
>> print("Init Stockable")
>>
>> class Character(Stockable):
>>
>> __tablename__ = 'characters'
>> id = Column(Integer, primary_key=True)
>>
>> def __init__(self, name):
>> self.name = name
>> print("Init character")
>>
>>
>> jean = Character("Jean")
>> print(jean.name)
>>
>>
>>
> this seems like roughly the correct approach.
>
>
>> It seems to work. I get the following result :
>>
>> >>>
>> Init MetaBase
>> Init MetaBase
>> Init MetaBase
>> Init compte
>> Jean
>> >>>
>>
>> However, the problem with this method is that I have to add *"__abstract__
>> = True" *to every class which is inherited by Stockable... so, about 400
>> classes.
>>
>
> I don't see why that is. If these classes are mapped to tables (which, if
> they are persisted, they are), then there is no reason to add
> "__abstract__". As in my previous email, how these 400 classes link
> to tables is what needs to be answered and then we can formulate the
> correct calling style.
>
>
>
>> It is not very clean. Is it possible to avoid that by using something
>> similar to my first code ? It would be great !
>>
>> Thank you very much.
>>
>> Sven
>>
>> --
>> SQLAlchemy -
>> The Python SQL Toolkit and Object Relational Mapper
>>
>> http://www.sqlalchemy.org/
>>
>> To post example code, please provide an MCVE: Minimal, Complete, and
>> Verifiable Example. See http://stackoverflow.com/help/mcve for a full
>> description.
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>
>
--
SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
To post example code, please provide an MCVE: Minimal, Complete, and Verifiable
Example. See http://stackoverflow.com/help/mcve for a full description.
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