Imports: de-duplicate some expensive calls

QMetaMethod::parameterNames() contains internal loop,
and we had quadratic behavior. Since operator[] was used
with temp object, also we had detach()ing.

QUrl::path() contains memory allocation.

To avoid these issues cache results of functions.

Change-Id: Ie4c3f0573a000342aff44de0dd4f744a146bb935
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

1 files changed, 3 insertions, 2 deletions

diff --git a/src/imports/folderlistmodel/qquickfolderlistmodel.cpp b/src/imports/folderlistmodel/qquickfolderlistmodel.cpp
index 66af37c40c..1c94fddecf 100644
--- a/src/imports/folderlistmodel/qquickfolderlistmodel.cpp
+++ b/src/imports/folderlistmodel/qquickfolderlistmodel.cpp
@@ -491,10 +491,11 @@ QUrl QQuickFolderListModel::parentFolder() const
             return QUrl();
         localFile = dir.path();
     } else {
-        const int pos = d->currentDir.path().lastIndexOf(QLatin1Char('/'));
+        const QString path = d->currentDir.path();
+        const int pos = path.lastIndexOf(QLatin1Char('/'));
         if (pos <= 0)
             return QUrl();
-        localFile = d->currentDir.path().left(pos);
+        localFile = path.left(pos);
     }
     return QUrl::fromLocalFile(localFile);
 }