ReStore newbie

Hi,

I have a Simple class hierarchy:
Bank
    accounts (Collection of: Account).
Account
    SpecialAccountA
    SpecialAccountB
    SpecialAccountC.

I can store aBank in the database but when I load it from the database this
variable (accounts) apperas as DBError.
Why ?
I suspect because there is not exists anAccount table, the tables are:
SpecialAccountA.
SpecialAccountB.
SpecialAccountC.

what i'm doing wrong ?

Regards
Bruno

Bruno wrote:
I haven't really used this aspect of ReStore, but I'll take a shot at
trying to help you out.

In your example, "accounts" as a collection of Accounts will only be
able to hold a mix of different subclasses of Account if they all share
a common table. Since the default is that a hierarchy of classes will
share a single table, I can think of a couple of things that may have
changed this.

You might have implemented either #shouldSubclassesInheritPersistency or
#shouldInheritPersisteny as "^false" which could cause separate tables
to be used. The other (more likely cause) is that Account class does not
itself define #addClassDefinitionTo:, such that ReStore does not treat
Account as a persistent class, only the subclasses.

HTH,
-Bill

-------------------------------------------
Bill Dargel            [hidden email]
Shoshana Technologies
100 West Joy Road, Ann Arbor, MI 48105  USA

> Bank
>     accounts (Collection of: Account).
> Account
>     SpecialAccountA
>     SpecialAccountB
>     SpecialAccountC.
>
> I can store aBank in the database but when I load it from the database
this
> variable (accounts) apperas as DBError.
> Why ?
> I suspect because there is not exists anAccount table, the tables are:
> SpecialAccountA.
> SpecialAccountB.
> SpecialAccountC.

Two options:
1. Separate accounts in three collections (with three db tables).
Bank
    specialsA Collection of: SpecialAccountA.
    specialsB Collection of: SpecialAccountB.
    specialsC Collection of: SpecialAccountC.

OR:
2. Share a table (only one db table).
Account table store all instances of:
    SpecialAccountA.
    SpecialAccountB.
    SpecialAccountC.

Regards Bruno

> In your example, "accounts" as a collection of Accounts will only be
> able to hold a mix of different subclasses of Account if they all share
> a common table. Since the default is that a hierarchy of classes will
> share a single table, I can think of a couple of things that may have
> changed this.

Yes, like you say i'm using a shared table.

Regards
Bruno

Bruno,

> Two options:
> 1. Separate accounts in three collections (with three db tables).
> ...
> 2. Share a table (only one db table).

You're right that Collections in ReStore have to contain objects of the same
class, or from the same hierarchy of persistent classes. If you're having
problems setting up this latter "shared table" approach, here's some pointers:

1) ensure the subclass (SpecialAccountA etc.) class definition method also
adds in the superclass definition, i.e.

SpecialAccountA>>addClassDefinitionTo: aClassDef

    super addClassDefinitionTo: aClassDef.

    aClassDef

        define: #...

2) ensure you're adding the superclass and all subclasses to ReStore:

aReStore addClassWithSubclasses: Account

3) Not actually related to persistent hierarchies, but I notice in your original
post you said 'accounts' was defined as (Collection of: Account) - you actually
need to specify a concrete collection class (e.g. OrderedCollection) rather than
the abstract Collection class.

Hope this helps - if you're still experiencing problems I can mail you an
example package.

Best regards,

John Aspinall
Solutions Software

> 3) Not actually related to persistent hierarchies, but I notice in your
original
> post you said 'accounts' was defined as (Collection of: Account) - you
actually
> need to specify a concrete collection class (e.g. OrderedCollection)
rather than
> the abstract Collection class.

I solve my problem with a shared table.

And the collection is actualy anOrderedCollection (my mistake in the mail).

Thanks Bruno