Solved QAbstractItemModel::match bug?

[Koyi]

I have a QCombobox wich model is a QSqlTableModel populated with a DataBase table:
Integer | String
=-=-=-=-=-=-=-=
        |
=-=-=-=-=-=-=-=
    0 | Normal
=-=-=-=-=-=-=-=
    1 | Leve
=-=-=-=-=-=-=-=
    2 | Moderado
=-=-=-=-=-=-=-=
    3 | Severo
=-=-=-=-=-=-=-=
   
the combobox works fine
but when I try to set the value in combo acording with the database table, I use this code

void MyComboBox::setValor(QVariant myValue)
{
QModelIndexList myFinded=this->model()->match(this->model()->index(0,0),Qt::DisplayRole,myValue,5,Qt::MatchFlags(Qt::MatchExactly || Qt::MatchWrap));

this->setCurrentIndex(myFinded[0].row());
}

When myValue is 1, myFinded has 1 Index (corresponding to row 2)
When myValue is 2, myFinded has 1 Index (corresponding to row 3)
and so on
but when myValue is 0, myFinded has 2 Index (corresponding to row 0 and 1)
I don't understand why. Is this a bug? Or am I doing something wrong

[SGaist]

Hi and welcome to devnet,

Did you check the content of myValue ?

[Koyi]

Hi
thanks for a quick answer.
yes, of course I checked the value of myValue and de value of MyFinded (debug mode).

Any idea?

[Koyi]

I found the problem (not the solution):(

QAbstractItemModel::match compares each value from the model with the searched value and return the indexes that match.
it uses the operator== method of QVariant, but it doesn't work fine

QVariant var1=QVariant(0); // variant containing the integer 0

QSqlQueryModel *miConsulta=new QSqlQueryModel;

miConsulta->setQuery("Select Valor, Descripcion From myTable");
QVariant var2=miConsulta->record(0).value(0);

I get
var1
value: 0
type: QVariant(int)
isnull: false

var2
value:0
type: QVariant(int)
isnull: true

but var1==var2 return TRUE !!!!!!!!!

how can a null variant be equal to anything?????????

[jeremy_k]

@Koyi The documentation mentions this:

"A variant is considered null if it contains a default constructed value or a built-in type instance that has an isNull method, in which case the result would be the same as calling isNull on the wrapped object.

Warning: The result of the function doesn't affect == operator, which means that two values can be equal even if one of them is null and another is not."

[VRonin]

can you consider manual matching?

void MyComboBox::setValor(const QVariant& myValue, int column = 0, int role = Qt::DisplayRole, const QModelIndex& parent=QModelIndex())
{
if(myValue.isNull()) return;
const int rowCount= model()->rowCount(parent);
for(int i=0;i<rowCount;++i){
const QVariant currVal = model()->index(i,column,parent ).data(role );
if(currVal.isNull()) continue;
if(currVal == myValue)
return setCurrentIndex(i);
}
}

[Koyi]

@jeremy_k said in QAbstractItemModel::match bug?:

@Koyi The documentation mentions this:

"A variant is considered null if it contains a default constructed value or a built-in type instance that has an isNull method, in which case the result would be the same as calling isNull on the wrapped object.

Warning: The result of the function doesn't affect == operator, which means that two values can be equal even if one of them is null and another is not."

You are right.
I expected that operator== were about

bool operator==(const QVariant &v1, const QVariant &v2)
{
  if (isnull(v1) || isnull(v2))
  return false;
.......
}

because I think a null value cannot be compared with anything.
Obviously I was wrong.

[Koyi]

@VRonin said in QAbstractItemModel::match bug?:

can you consider manual matching?

void MyComboBox::setValor(const QVariant& myValue, int column = 0, int role = Qt::DisplayRole, const QModelIndex& parent=QModelIndex())
{
if(myValue.isNull()) return;
const int rowCount= model()->rowCount(parent);
for(int i=0;i<rowCount;++i){
const QVariant currVal = model()->index(i,column,parent ).data(role );
if(currVal.isNull()) continue;
if(currVal == myValue)
return setCurrentIndex(i);
}
}

yes, it seems to be the approach.
thanks