jaydata: how to correctly "load" an entity for being edited?

Question

This code should run as is in your browser.

<!DOCTYPE html>
<html>
    <head>
        <title>JayData testing</title>

        <script type="text/javascript" src="jquery-1.9.1.js"></script>
        <script type="text/javascript" src="jaydata.js"></script>
        <script type="text/javascript" src="SqLiteProvider.js"></script>

        <script type="text/javascript">

            $data.Entity.extend('$data.Types.ReferencedEntity', {
                Oid: {type: $data.Integer, key: true, computed: true},
                Codigo: {type: $data.String},
                Nombre: {type: $data.String},
                MainsByOne: {type: $data.Array, elementType: '$data.Types.MainEntity', inverseProperty: 'ReferenceOne'},
                MainsByTwo: {type: $data.Array, elementType: '$data.Types.MainEntity', inverseProperty: 'ReferenceTwo'}
            });

            $data.Entity.extend('$data.Types.MainEntity', {
                Oid: {type: $data.Integer, key: true, computed: true},
                Codigo: {type: $data.String},
                ReferenceOne: {type: '$data.Types.ReferencedEntity', inverseProperty: 'MainsByOne'},
                ReferenceTwo: {type: '$data.Types.ReferencedEntity', inverseProperty: 'MainsByTwo'}
            });

            $data.EntityContext.extend('$data.Types.LocalDBContext', {
                ReferencedEntities: {type: $data.EntitySet, elementType: $data.Types.ReferencedEntity},
                MainEntities: {type: $data.EntitySet, elementType: $data.Types.MainEntity}
            });

            window.app = {};

            app.localdb = new $data.Types.LocalDBContext({
                name: 'webSql',
                databaseName: 'Test',
                version: "1.0",
                maxSize: 5 * 1024 * 1024,
                dbCreation: $data.storageProviders.DbCreationType.DropTableIfChanged
            });

            app.localdb.onReady(function() {
                console.log("smarterpjs.localdb.onReady!");
            });

            app.run = function() {
                /* Create the entities */
                var a = new $data.Types.ReferencedEntity();
                app.localdb.ReferencedEntities.add(a);
                a.Codigo = 'UNI';
                a.Nombre = 'UNIDAD';

                var m = new $data.Types.MainEntity();
                app.localdb.MainEntities.add(m);
                m.Codigo = 'MAIN';
                m.ReferenceOne = a;
                m.ReferenceTwo = a;

                app.localdb.saveChanges();

                /* Now query for editing... */

                var query = app.localdb.MainEntities
                        .include('ReferenceOne')
                        .include('ReferenceTwo')
                        .filter(function(m) {
                            return m.Codigo === 'MAIN';
                        }, undefined)
                        .first();

                query.then(function(result) {
                    /* As i need to 'edit' the result
                     * then i must attach the MainEntity itself,
                     * and the referenced objects ReferenceOne, and ReferenceTwo
                     */
                    app.localdb.attach(result);
                    app.localdb.attach(result.ReferenceOne);

                    /* The problem comes here, 
                     * as the entity Codigo 'MAIN' references on both fields 'ReferenceOne' and 'ReferenceTwo'
                     * the same 'ReferencedEntity'
                     */
                    app.localdb.attach(result.ReferenceTwo);
                });
            }

        </script>
    </head>
    <body>
        <div onclick="app.run()">CLICK ME!</div>
    </body>
</html>

Having that test app for jaydata, my question is embedded on the very same code. But i'try to explain more: i have a MainEntity table with 2 fields pointing to another ReferencedEntity table. For example:

ReferencedEntities = [ { Codigo: 'UNI' } ]
MainEntities = [ { 
 Codigo: 'MAIN', 
 ReferenceOne: { Codigo: 'UNI' } , 
 ReferenceTwo: { Codigo: 'UNI' }
}

With this very simple data, when i try to load just one MainEntity for having it available completely, so the user can edit any of their fields, i get this error of:

**Context already contains this entity!!!**

Hope i get my point, and also the code runs showing the problem with current v1.3.2 of jaydata.

EDIT:

I've found "the way" to get a fully loaded object with its references, with an easy code.

The change is on the query.then(), as follows:

query.then(function(result) {
  app.localdb.attach(result);
  result.ReferenceOne = app.localdb.attachOrGet(result.ReferenceOne);
  result.ReferenceTwo = app.localdb.attachOrGet(result.ReferenceTwo);
});

That way:

I load every referenced entity always with attachOrGet, in case it is already on the context
I assign each returned object to the original one, so the final "result" as everything in place for editing that instance, saving, and saving changes

Hope somebody find this useful!

score 0 · Answer 1 · answered Oct 31 '13 at 20:13

0

I do not think that it will work. You can try to use attachOrGet when you attach the second child..

answered Oct 31 '13 at 20:13

Gabor Dolla

2,680
4
14
13

That way, first i already must know that the second line "will" throw an error cause ReferenceOne and ReferenceTwo are equal, and then, use attachOrGet which will give me a new object, and set it to the previous one with result.ReferenceTwo = ... attachOrGet(result.ReferenceTwo) . Is that what you mean? – Javier Castro Oct 31 '13 at 20:26
attachOrGet gives you the object that is in the context already or attaches the parameter. – Gabor Dolla Nov 04 '13 at 12:25

jaydata: how to correctly "load" an entity for being edited?

1 Answers1