Doc: Make QListIterator snippets more robust

qDebug() << i.next();

can become a NOOP if the code is compiled with QT_NO_DEBUG_OUTPUT.

Pick-to: 5.15 6.2 6.3
Fixes: QTBUG-97535
Change-Id: I9085b40ac9b4de2bb06f16e03fd5100902b08d4f
Reviewed-by: Marc Mutz <marc.mutz@qt.io>

src/corelib/doc/snippets/code/doc_src_containers.cpp

@@ -70,7 +70,7 @@ list << "A" << "B" << "C" << "D";
 
 QListIterator<QString> i(list);
 while (i.hasNext())
-    qDebug() << i.next();
+    QString s = i.next();
 //! [1]
 
 
@@ -78,7 +78,7 @@ while (i.hasNext())
 QListIterator<QString> i(list);
 i.toBack();
 while (i.hasPrevious())
-    qDebug() << i.previous();
+    QString s = i.previous();
 //! [2]
 
 
@@ -216,8 +216,10 @@ foreach (str, values)
 QList<QString> values;
 ...
 QListIterator<QString> i(values);
-while (i.hasNext())
-    qDebug() << i.next();
+while (i.hasNext()) {
+    QString s = i.next();
+    qDebug() << s;
+}
 //! [16]
 
 

src/corelib/doc/snippets/code/doc_src_qiterator.cpp

@@ -53,7 +53,7 @@ QList<float> list;
 ...
 QListIterator<float> i(list);
 while (i.hasNext())
-    qDebug() << i.next();
+    float f = i.next();
 //! [0]
 
 
@@ -61,7 +61,7 @@ while (i.hasNext())
 QListIterator<float> i(list);
 i.toBack();
 while (i.hasPrevious())
-    qDebug() << i.previous();
+    float f = i.previous();
 //! [1]
 
 //! [6]
@@ -69,7 +69,7 @@ QSet<QString> set;
 ...
 QSetIterator<QString> i(set);
 while (i.hasNext())
-    qDebug() << i.next();
+    float f = i.next();
 //! [6]
 
 
@@ -77,7 +77,7 @@ while (i.hasNext())
 QSetIterator<QString> i(set);
 i.toBack();
 while (i.hasPrevious())
-    qDebug() << i.previous();
+    QString s = i.previous();
 //! [7]
 
 
@@ -86,7 +86,7 @@ QList<float> list;
 ...
 QMutableListIterator<float> i(list);
 while (i.hasNext())
-    qDebug() << i.next();
+    float f = i.next();
 //! [8]
 
 
@@ -94,7 +94,7 @@ while (i.hasNext())
 QMutableListIterator<float> i(list);
 i.toBack();
 while (i.hasPrevious())
-    qDebug() << i.previous();
+    float f = i.previous();
 //! [9]
 
 
@@ -115,7 +115,7 @@ QSet<float> set;
 ...
 QMutableSetIterator<float> i(set);
 while (i.hasNext())
-    qDebug() << i.next();
+    float f = i.next();
 //! [17]
 
 //! [19]

src/corelib/doc/snippets/code/doc_src_qset.cpp

@@ -73,8 +73,10 @@ if (!set.contains("ninety-nine"))
 
 //! [4]
 QSetIterator<QWidget *> i(set);
-while (i.hasNext())
-    qDebug() << i.next();
+while (i.hasNext()) {
+    QWidget *w = i.next();
+    qDebug() << w;
+}
 //! [4]
 
 

src/corelib/doc/snippets/code/src_corelib_io_qdiriterator.cpp

@@ -51,8 +51,8 @@
 //! [0]
 QDirIterator it("/etc", QDirIterator::Subdirectories);
 while (it.hasNext()) {
-    qDebug() << it.next();
-
+    QString dir = it.next();
+    qDebug() << dir;
     // /etc/.
     // /etc/..
     // /etc/X11

src/corelib/doc/snippets/code/src_corelib_text_qstringiterator.cpp

@@ -63,7 +63,7 @@ QStringIterator i(string); // implicitly converted to QStringView
 
 //! [1]
 while (i.hasNext())
-    qDebug() << i.next();
+    uint c = i.next();
 //! [1]
 }
 

src/corelib/doc/snippets/code/src_corelib_thread_qfuture.cpp

@@ -62,7 +62,7 @@ QFuture<QString> future;
 ...
 QFutureIterator<QString> i(future);
 while (i.hasNext())
-    qDebug() << i.next();
+    QString s = i.next();
 //! [1]
 
 
@@ -70,7 +70,7 @@ while (i.hasNext())
 QFutureIterator<QString> i(future);
 i.toBack();
 while (i.hasPrevious())
-    qDebug() << i.previous();
+    QString s = i.previous();
 //! [2]
 
 //! [3]

src/corelib/doc/src/java-style-iterators.qdoc

@@ -71,7 +71,7 @@
     \image javaiterators1.png
 
     Here's a typical loop for iterating through all the elements of a
-    QList<QString> in order and printing them to the console:
+    QList<QString> in order:
 
     \snippet code/doc_src_containers.cpp 1