Allow resetting foreign key in QSqlRelationalTableModel

Change the QSqlRelationalTableModel::setData() method to remove the
associated foreign key, if called on a relational column.

Task-number: QTBUG-47713
Change-Id: Ib3cf03f1da506d63f1a59349d64d5da45bde4137
Reviewed-by: Axel Spoerl <[email protected]>

2 files changed, 24 insertions, 3 deletions

diff --git a/src/sql/models/qsqlrelationaltablemodel.cpp b/src/sql/models/qsqlrelationaltablemodel.cpp
index d892be070e7..29beefb94db 100644
--- a/src/sql/models/qsqlrelationaltablemodel.cpp
+++ b/src/sql/models/qsqlrelationaltablemodel.cpp
@@ -428,8 +428,9 @@ QVariant QSqlRelationalTableModel::data(const QModelIndex &index, int role) cons
     example, if \a index is out of bounds).
 
     For relational columns, \a value must be the index, not the
-    display value. The index must also exist in the referenced
-    table, otherwise the function returns \c false.
+    display value. If an index is given, it must also exist in the
+    referenced table, otherwise the function returns \c false.
+    If a QVariant() is passed instead of an index, the index is cleared.
 
     \sa editStrategy(), data(), submit(), revertRow()
 */
@@ -442,7 +443,7 @@ bool QSqlRelationalTableModel::setData(const QModelIndex &index, const QVariant
         auto relation = d->relations.at(index.column());
         if (!relation->isDictionaryInitialized())
             relation->populateDictionary();
-        if (!relation->dictionary.contains(value.toString()))
+        if (value.isValid() && !relation->dictionary.contains(value.toString()))
             return false;
     }
     return QSqlTableModel::setData(index, value, role);
diff --git a/tests/auto/sql/models/qsqlrelationaltablemodel/tst_qsqlrelationaltablemodel.cpp b/tests/auto/sql/models/qsqlrelationaltablemodel/tst_qsqlrelationaltablemodel.cpp
index aaf55da6e18..3879c0f2ae4 100644
--- a/tests/auto/sql/models/qsqlrelationaltablemodel/tst_qsqlrelationaltablemodel.cpp
+++ b/tests/auto/sql/models/qsqlrelationaltablemodel/tst_qsqlrelationaltablemodel.cpp
@@ -402,6 +402,26 @@ void tst_QSqlRelationalTableModel::setData()
         QCOMPARE(model.data(model.index(0,1)).toString(), QString("Hr"));
     }
 
+    // verify that clearing a foreign key works
+    {
+        QSqlRelationalTableModel model(0, db);
+
+        model.setTable(reltest1);
+        model.setRelation(2, QSqlRelation(reltest2, "id", "title"));
+        model.setSort(0, Qt::AscendingOrder);
+        QVERIFY_SQL(model, select());
+
+        QVERIFY(model.setData(model.index(0, 1), QString("harry2")));
+        QVERIFY(model.setData(model.index(0, 2), 2));
+
+        QCOMPARE(model.data(model.index(0, 1)).toString(), QString("harry2"));
+        QCOMPARE(model.data(model.index(0, 2)).toString(), QString("mister"));
+
+        QVERIFY(model.setData(model.index(0, 2), QVariant())); // clear foreign key
+
+        QCOMPARE(model.data(model.index(0, 1)).toString(), QString("harry2"));
+        QCOMPARE(model.data(model.index(0, 2)).toString(), QString()); // check that foreign value is not visible
+    }
 }
 
 void tst_QSqlRelationalTableModel::multipleRelation()