On 14 December 2011 20:40, Daniel Espinosa eso...@gmail.com wrote:
2011/12/14 Vivien Malerba vmale...@gmail.com:
On 13 December 2011 22:39, Daniel Espinosa eso...@gmail.com wrote:
2011/12/13 Vivien Malerba vmale...@gmail.com:
On 13 December 2011 18:22, Daniel Espinosa eso...@gmail.com wrote:
I'm continue in development of Vala extensions on libgda-vala branch,
I can't tell that is API stable, then I don't merge soon.
But what about to branch 5.0 development and make master point to 6.0
unstable. May we can make API/ABI changes like the ones on
GdaNumeric,
I would like to do the same for most GDA structs (GdaBlob and others)
to add API to access its members.
I've just created the LIBGDA_5.0 branch for the next 5.0.x releases,
and
now
the master branch will be used for the 5.2 release later on, so you'll
have
to merge your branch into master without any perturbation to the 5.0.x
versions.
Thanks I'll do it ASAP.
Even I figure out how to make GdaDataModel a Gee Collection like or
even add LINQ[1] features to Vala using Gee interfaces and GDA as
backend.
I'm afraid you'll have to illustrate with an example so I can
understand
fully what you did.
I did:
* Added a DataModelIterable, this object can be used in foreach
instructions in Vala or using while instrucctions using standard Gee
Iterators, to filter GValues or chop a number of GValues. This makes a
DataModel a linear collection of GValue where you can traverse through
one per one. This is a proof of concept about to use Gee Collection
interfaces.
The GdaDataModelIter object is an iterator over data models. Did you
wrap
it or create a new object?
For now I have created a new GObject with a reference to a
GdaDataModelIter created when my object (Gda.DataModelIterator) from a
GdaDataModel using create_iter(). Then this reference is used
internally to iterate over the DataModel by implemented
Gee.AbstractCollection.abstract class.
Ok, that looks good!
* Added a DataObject to create persistence database objects, you
derive objects form Gda.DataObject to modify values in a row in a
table.
Could you illustrate its usage with an example?
I'm writing an example in samples/vala. This is to create a micro
Accounting system (I've liked to write it for a long time), a Book,
Account(s) and Transaction(s). This will demostrate the use of
GdaData.Object, to manage persistence objects in a database using a
simple GObjects. Is a work in progress.
If the example is very simple and can be kept to a few files then Ok,
otherwise I prefer to have several small examples, each to illustrate a
specific problem (see my previous mail). If the example is too big, one can
get lost and the didactic value is lost.
If you agree, I can merge inmediatly following commit often, commit
early, in order to show progress and drawbacks!
Yes, that's the best!
Work in progress:
* Implementing GdaDataModel Interface in the iterable object (just
wraps an internal reference to a GdaDataModel)
* Implementing Gee.Collection interface to manage DataModel's GValue
as a Collection
Future Ideas:
* How to make use of GDA a Collection provider. Programers will be able
to:
- Access GValue stored in a table by using Gee interfaces
- Access Rows in the table and filter them by using fields value
expressions. This may requires to modify or add a new interface to Gee
like a Collection of Hashes, each hash have field name as key and a
GValue as value
- Filter Data from a database using commands like LINQ by compling
using Vala. GDA can be called by Vala to pass a string representation
of the query to execute a query to the database and return a
Gee.Collection. This may require for GDA to parse these kind of SQL
commands. A LINQ example code from Wikipedia is:
int someValue = 5;
var results = from c in SomeCollection
where c.SomeProperty someValue * 2
select new {c.SomeProperty, c.OtherProperty};
foreach (var result in results)
{
Console.WriteLine(result);
}
* Ideally All providers could return just Iterable and Collection
DataModels, but that requires to modify providers implementation. As
Vala can create C code to refer to, may be using conditionals is
possible to include libgdadata.h to return iterable objects.
All providers return a GdaDataSelect object, which can be used to write
data
back to the database. This object is quite complicated, and I don't plan
to
remove it, but if you need some more features out of it, it can of
course be
modified.
I think that for now GdaDataSelect must stay *as is* for now. I think
to do thinks like:
/* Code in providers to create a GdaDataSelect Object */
#ifdef ENABLE_VALA_EXTENSIONS
return gda_data_data_model_iterable_new (dataselectobject);
