From: "Samuel Pelletier" <webobjects-dev@wocommunity.org>
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Subject: Re: [WO-DEV] localinstance for not-yet-saved EOs? 
Date: Sun, 17 Oct 2021 11:47:20 -0400
References: <list-26609967@post.selbstdenker.com>
To: WebObjects & WOnder Development <webobjects-dev@wocommunity.org>
In-Reply-To: <list-26609967@post.selbstdenker.com>
Message-Id: <3F1B4B57-204E-470F-9C79-6162CAE2F39C@samkar.com>

Hi Markus,

Passing an EO to another EditingContext requires that this EO exists in =
the parent object store of the new ec knows about this EOGlobalID to =
retrieve the data snapshot.

If an object is committed to the database, the root ObjectStore can =
retrieve it's data from the DB so it always works.

In your case, I see 2 solutions, both require that the ec used in the =
picking phase know about the main ec use to edit the main object. If you =
pass the main object (even if not saved yet, you can get it's ec.

1- You use the main edited object's EOEditingContext in the picker but =
you loose the isolation if the changes...

2- You use the main edited object ec as the parent object store of the =
picking EOEditingContext like this:

	EOEditingContext ec =3D ERXEC.newEditingContext(); // Main ec
	EOEditingContext subEc =3D ERXEC.newEditingContext(ec);  // In =
the picking sub component

With solution 2, saving into subEc will commit the changes to the main =
ec (nothing sent to the database yet). You can then localInstance =
objects from the sebEc into the main ec.

You can cascade this as deep or wide as required.

Hope this can help you,

Samuel


> Le 15 oct. 2021 =C3=A0 08:48, Markus Ruggiero (rucotec) =
<webobjects-dev@wocommunity.org> a =C3=A9crit :
>=20
> LocalInstance is only allowed for EOs that have already been saved. If =
isNewObject() return true then any form of localinstance call returns an =
exception. Why? And how can I overcome this?
>=20
> I have the following scenario:=20
>=20
> The user picks existing EOs to be worked on at a later point in time. =
They can also create on-the-fly new EOs for picking. All EOs as well as =
the new ones are associated with the current editing context. The whole =
list of picked objects (NSArray containing existing and new EOs) is then =
passed to the next page and on to the next. In each step some of the EOs =
are modified in various ways until about 3 steps down the line a final =
saveChanges() is done. All fine so far.=20
>=20
> But on each step the user can go back up one step (either browser back =
button or with a dedicated navigation button on the page). The page =
cache takes care of this but the EOs themselves are not in the page =
cache and remain modified in their EC. Coming back the previous / first =
page does not show the initial state anymore. Ok, easy to solve =
(methinks): map the EOs into a new editing context right before going to =
the next step. Coming back then automatically throws away that EC. Going =
forward again will create a brand new EC. But! localInstancing into the =
new EC only works for saved EOs. How do I get these new EOs into the =
nextPhaseEC? The new EOs are fairly complex and already have =
relationships to other EOs. How can I re-wire the new EOs?
>=20
> Thanks for any help
> ---markus---
>=20