QSql*Model + QTreeView : make a tree

[punkypogo]

Hello,

I would like to have the data contained in an SQL table shown in a treeview (I already have that), but I would like items to be group (kind of filter) by types. See the exemple.

Here is my table "MultimediaFiles" structure:
- id,
- name,
- path,
- type (can be, "picture", "video", "sound").

So, I would like my records to be presented in a treeview like this :

|-- Name --|-- Path --|

------------------------------------
- picture

|- foo.png C:\...

- video

|- bar.avi C:\...
|- toto.mpg C:\...

- sound

|- huhu.wav ...
|- haha.mp3 C:\...

What I already did :

SQL::SQL()
{
	QSqlDatabase mDb = QSqlDatabase::addDatabase( "QMYSQL" );
	mDb.setHostName( "localhost" );
	mDb.setDatabaseName( "mydb" );
	mDb.open();
	setupModel();
}
 
void SQL::setupModel()
{
	pModel = new QSqlRelationalTableModel();
	pModel->setTable( "MultimediaFiles" );
	if( !pModel->select() )
	{
		qDebug() << "pb select";
		qDebug() << pModel->lastError().text();
	}
 
	treeView->setModel( pModel );
/*...*/
	treeView->show();
}

SQL::SQL()
{
	QSqlDatabase mDb = QSqlDatabase::addDatabase( "QMYSQL" );
	mDb.setHostName( "localhost" );
	mDb.setDatabaseName( "mydb" );
	mDb.open();
	setupModel();
}

void SQL::setupModel()
{
	pModel = new QSqlRelationalTableModel();
	pModel->setTable( "MultimediaFiles" );
	if( !pModel->select() )
	{
		qDebug() << "pb select";
		qDebug() << pModel->lastError().text();
	}

	treeView->setModel( pModel );
/*...*/
	treeView->show();
}

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But it doesn't act as I want : there is no node created.
So, do I miss something, or do I need to make my own model, or add treeItems by hands ?



Thanks in advance.

[wysota]

The model you used is a flat model and no matter what view you use it won't become structured just by itself. You need to provide a proxy model that will represent your table as a tree. See QAbstractProxyModel for details.

[punkypogo]

Great, I take a look.

Thank you.

[punkypogo]

I'm back. I'm totally lost :/

I understood I have to subclass QAbstractProxyModel, but I really don't know what to write in the methods.
Could you please help me a little bit ?

[wysota]

The proxy is to transform a flat model into a tree. You need to return proper model indexes and parent indexes. If you don't feel comfortable enough with implementing your own proxy model (which is not very simple) I suggest you use QStandardItemModel and manually fill it with data fetched from the sql table.

[punkypogo]

Hello,

Well, I want to learn, so I will try to make a proxy.

Tell me if I'm wrong :
- I create a TreeModel class (based on the Simple Tree model example from doc.trolltech.com)
- Every time my Qsql*Model will change, I will populate my TreeModel through the Proxy.
- The proxy will make the correspondance between the Qsl*Model and my TreeModel.

Does it sound good ?

[wysota]

No. You need to subclass QAbstractProxyModel.

[vladeck]

ProxyModel is deprecated... You should take a look at simple tree view example. You can make a tree model from flat sql result by choosing what columns will be the tree parent creating initiator (I'm bad with english )

For example:

Column_001 | Column_002
-----------+-----------
value_001  | value002
value_001  | value003
value_002  | value004
value_002  | value005
value_003  | value006

Column_001 | Column_002
-----------+-----------
value_001  | value002
value_001  | value003
value_002  | value004
value_002  | value005
value_003  | value006

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You should get (with the use of some code logic):

value_001
  +-- value_002
  +-- value_003
value_002
  +-- value_004
  +-- value_005
value_003
  +-- value_006

value_001
  +-- value_002
  +-- value_003
value_002
  +-- value_004
  +-- value_005
value_003
  +-- value_006

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[patrik08]

I build mysql netset on a tree ... to infinit loop whithout proxie or so..
The query is long but running...

#define TREECAT "SELECT n.*, round((n.rgt-n.lft-1)/2,0) AS childs, count(*)+(n.lft>1) AS level, ((min(p.rgt)-n.rgt-(n.lft>1))/2) > 0 AS lower, (( (n.lft-max(p.lft)>1) )) AS upper FROM FAKTURA_SUB n, FAKTURA_SUB p WHERE n.lft BETWEEN p.lft AND p.rgt AND (p.root_id = n.root_id) AND (p.id != n.id OR n.lft = 1) GROUP BY n.root_id,n.id ORDER BY n.root_id,n.lft"

You running only level 1 rows and append to QStandardItemModel(); root
all sub level go to self on composing ....
and you can move level up or dow append ....

a tree online demo http://www.klempert.de/nested_sets/demo/

QList<QStandardItem *> Cat_Tree::Compose( int rowposition )
{
    QSqlRecord r = ReadModel->record(rowposition);
    int level;
    int childs;
    QList<QStandardItem *> Horrizzontal_Line;
    for (int x = 0; x < DisplayFields.size(); ++x) {
 
            Horrizzontal_Line.append( xxxxx )
    }
    /* check on qmap unique ! */
    if (!OnBox(rowposition)) {
       RowUnique.insert(rowposition,level); 
    }
    /* if moore childs append .....  loops */
    if (childs > 0 ) {
        for (int i = 0; i < childs; ++i) {
        const int jumpto = i + 1 + rowposition;
          if (!OnBox(jumpto)) {  
              diritto.first()->appendRow(Compose(jumpto));
          }
        }
    }
return diritto;
}

QList<QStandardItem *> Cat_Tree::Compose( int rowposition )
{
    QSqlRecord r = ReadModel->record(rowposition);
    int level;
    int childs;
    QList<QStandardItem *> Horrizzontal_Line;
    for (int x = 0; x < DisplayFields.size(); ++x) {
              
            Horrizzontal_Line.append( xxxxx )
    }
    /* check on qmap unique ! */
    if (!OnBox(rowposition)) {
       RowUnique.insert(rowposition,level); 
    }
    /* if moore childs append .....  loops */
    if (childs > 0 ) {
        for (int i = 0; i < childs; ++i) {
        const int jumpto = i + 1 + rowposition;
          if (!OnBox(jumpto)) {  
              diritto.first()->appendRow(Compose(jumpto));
          }
        }
    }
return diritto;
}

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[wysota]

ProxyModel is deprecated...

Oh, really? Very interesting... since when?

[jacek]

Oh, really? Very interesting... since when?

4.1 or something. Just when QAbstractProxyModel and QSortFilterProxyModel came in to replace it.

[wysota]

4.1 or something. Just when QAbstractProxyModel and QSortFilterProxyModel came in to replace it.

Gee... isn't that QAbstractProxyModel I was writing about? I could have sworn the "abstract" word was there... and it still is, isn't it?