Re: [Vala] Writing objects to files

[Steven Oliver <oliver steven gmail com>]

I have not tried gom yet, but I did try the Json.gobject_serialize()
method as described by Christian Hergert. It almost does what I need
it to. It has some odd limitations.

For example, if this is your object everything works exactly as you
would expect.
public class MyObject : Object {
     public string str { get; set; }
     public MyEnum en { get; set; }
     public int num { get; set; }

     public MyObject (string str, MyEnum en, int num) {
         this.str = str;
         this.num = num;
         this.en = en;
     }
 }

On the other hand, though, if you throw in some kind of data structure
besides your basic types (int, string, etc.) it completely fails.
public class MyObject : Object {
     public string str { get; set; }
     public MyEnum en { get; set; }
     public int num { get; set; }
     public int[] data;

     public MyObject (string str, MyEnum en, int num) {
         this.str = str;
         this.num = num;
         this.en = en;
         this.data = {1,2,3,4,5};
     }
 }

Naturally, in my case I have complex data structures in my class so
the Json method did not work for me.
Steven N. Oliver


On Mon, Mar 26, 2018 at 5:09 PM, Vivien Kraus <vivien planete-kraus eu> wrote:
> Hello,
>
> I don't know what it's worth, but if you prefer XML this seems to be a
> good solution: https://blogs.gnome.org/despinosa/2016/05/04/howto-gobje
> ct-serialization-to-xml-using-gxml/
>
> Vivien
>
> Le lundi 26 mars 2018 à 14:02 -0700, Christian Hergert a écrit :
> > On 03/26/2018 11:44 AM, Steven Oliver wrote:
> > > I want to implement "saving" in my program. The data I want to save
> > > is
> > > a custom object. Is it possible in vala to simply write the object
> > > to
> > > disk (in binary I assume) without having to implement a to_string
> > > method?
> > >
> > > It seems like such a simple concept yet i can't seem to figure out
> > > how
> > > to do it in Vala.
> >
> > A very simple option (assuming you don't have an object graph to
> > serialize) could be to use either:
> >
> >   Json.gobject_serialize()
> >   Json.gobject_to_data()
> >
> > to serialize and
> >
> >   Json.gobject_deserialize()
> >   Json.gobject_from_data()
> >
> > to deserialize. If you need custom hooks into what will get
> > serialized,
> > you can implement Json.Serializable.
> >
> > If you really want binary, GVariant is a rather nice serialization
> > format, but you might need to bring your own serializers. Json-GLib
> > has
> > some code for working with GVariant too, but I've not used it.
> >
> > If you need an object graph, the Gom¹ library I made several years
> > back
> > can help, but it is more intrusive on your object design. I've only
> > used
> > it from C, but others have used it from Gjs, so I would expect it to
> > work in some form from Vala.
> >
> > -- Christian
> >
> > ¹ https://git.gnome.org/browse/gom
> > _______________________________________________
> > vala-list mailing list
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> > https://mail.gnome.org/mailman/listinfo/vala-list
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