Replace confusing member variable with a predicate

The Converter class, in the eponymous example, had a null member
variable that wasn't a nullptr - it pointed to an instance of
NullConverter - so that other converters could test whether a
Converter * they'd been passed was null (in the sense of pointing to a
NullConverter). This, however, was susceptible to misreading - I
misread one such comparison as a nullptr check and thus thought it
redundant with an earlier actual nullptr check. To spare future
readers similar confusion, replace the public static member variable
with a protected (since only other derived classes need it) static
predicate, to at least give the reader a clue that this is using the
word null in a class-specific sense.

Pick-to: 6.6 6.5
Task-number: QTBUG-111228
Change-Id: I1e4f494b303d1bf90107f8c6fa3a4a22f6d81b90
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/examples/corelib/serialization/convert/jsonconverter.cpp b/examples/corelib/serialization/convert/jsonconverter.cpp
index 6c307cdb8c..611061705b 100644
--- a/examples/corelib/serialization/convert/jsonconverter.cpp
+++ b/examples/corelib/serialization/convert/jsonconverter.cpp
@@ -76,7 +76,7 @@ QVariant JsonConverter::loadFile(QIODevice *f, const Converter *&outputConverter
         qFatal("Could not parse JSON content: offset %d: %s",
                error.offset, qPrintable(error.errorString()));
     }
-    if (outputConverter == null)
+    if (isNull(outputConverter))
         return QVariant();
     return doc.toVariant();
 }