Add an example of error handling of QFuture without using exceptions

Also fixed a few unrelated typos in docs.

Task-number: QTBUG-83236
Change-Id: I776cda8f0ef4de6c4a93e94092dc19e94d1884c8
Reviewed-by: Vitaly Fanaskov <vitaly.fanaskov@qt.io>
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>

1 files changed, 27 insertions, 0 deletions

diff --git a/src/corelib/doc/snippets/code/src_corelib_thread_qfuture.cpp b/src/corelib/doc/snippets/code/src_corelib_thread_qfuture.cpp
index dfa9b670e7..4fe3f7e99e 100644
--- a/src/corelib/doc/snippets/code/src_corelib_thread_qfuture.cpp
+++ b/src/corelib/doc/snippets/code/src_corelib_thread_qfuture.cpp
@@ -72,3 +72,30 @@ i.toBack();
 while (i.hasPrevious())
     qDebug() << i.previous();
 //! [2]
+
+//! [3]
+using NetworkReply = std::variant<QByteArray, QNetworkReply::NetworkError>;
+
+enum class IOError { FailedToRead, FailedToWrite };
+using IOResult = std::variant<QString, IOError>;
+//! [3]
+
+//! [4]
+QFuture<IOResult> future = QtConcurrent::run([url] {
+        ...
+        return NetworkReply(QNetworkReply::TimeoutError);
+}).then([](NetworkReply reply) {
+    if (auto error = std::get_if<QNetworkReply::NetworkError>(&reply))
+        return IOResult(IOError::FailedToRead);
+
+    auto data = std::get_if<QByteArray>(&reply);
+    // try to write *data and return IOError::FailedToWrite on failure
+    ...
+});
+
+auto result = future.result();
+if (auto filePath = std::get_if<QString>(&result)) {
+    // do something with *filePath
+else
+    // process the error
+//! [4]