diff --git a/resources/desktop/com.github.rssguard.appdata.xml b/resources/desktop/com.github.rssguard.appdata.xml
index cb454eccc..303260415 100644
--- a/resources/desktop/com.github.rssguard.appdata.xml
+++ b/resources/desktop/com.github.rssguard.appdata.xml
@@ -30,7 +30,7 @@
   <url type="donation">https://martinrotter.github.io/donate/</url>
   <content_rating type="oars-1.1" />
   <releases>
-    <release version="3.9.0" date="2021-03-17"/>
+    <release version="3.9.0" date="2021-03-19"/>
   </releases>
   <content_rating type="oars-1.0">
     <content_attribute id="violence-cartoon">none</content_attribute>
diff --git a/src/librssguard/gui/settings/settingsgui.cpp b/src/librssguard/gui/settings/settingsgui.cpp
index ba5e6ffed..8ec2661b7 100755
--- a/src/librssguard/gui/settings/settingsgui.cpp
+++ b/src/librssguard/gui/settings/settingsgui.cpp
@@ -99,8 +99,9 @@ void SettingsGui::loadSettings() {
 
   // Load settings of icon theme.
   const QString current_theme = qApp->icons()->currentIconTheme();
+  auto icons = qApp->icons()->installedIconThemes();
 
-  for (const QString& icon_theme_name : qApp->icons()->installedIconThemes()) {
+  for (const QString& icon_theme_name : qAsConst(icons)) {
     if (icon_theme_name == APP_NO_THEME) {
       // Add just "no theme" on other systems.
       //: Label for disabling icon theme.
@@ -129,8 +130,9 @@ void SettingsGui::loadSettings() {
 
   // Load skin.
   const QString selected_skin = qApp->skins()->selectedSkinName();
+  auto skins = qApp->skins()->installedSkins();
 
-  for (const Skin& skin : qApp->skins()->installedSkins()) {
+  for (const Skin& skin : qAsConst(skins)) {
     QTreeWidgetItem* new_item = new QTreeWidgetItem(QStringList() <<
                                                     skin.m_visibleName <<
                                                     skin.m_version <<
@@ -155,7 +157,9 @@ void SettingsGui::loadSettings() {
   }
 
   // Load styles.
-  for (const QString& style_name : QStyleFactory::keys()) {
+  auto styles = QStyleFactory::keys();
+
+  for (const QString& style_name : qAsConst(styles)) {
     m_ui->m_cmbStyles->addItem(style_name);
   }
 
diff --git a/src/librssguard/gui/settings/settingslocalization.cpp b/src/librssguard/gui/settings/settingslocalization.cpp
index f519ff68e..4e6fc68c3 100644
--- a/src/librssguard/gui/settings/settingslocalization.cpp
+++ b/src/librssguard/gui/settings/settingslocalization.cpp
@@ -32,7 +32,9 @@ SettingsLocalization::~SettingsLocalization() {
 void SettingsLocalization::loadSettings() {
   onBeginLoadSettings();
 
-  for (const Language& language : qApp->localization()->installedLanguages()) {
+  auto langs = qApp->localization()->installedLanguages();
+
+  for (const Language& language : qAsConst(langs)) {
     auto* item = new QTreeWidgetItem(m_ui->m_treeLanguages);
 
     item->setText(0, language.m_name);
diff --git a/src/librssguard/gui/webviewer.cpp b/src/librssguard/gui/webviewer.cpp
index 666b9844c..5c09d4d3c 100644
--- a/src/librssguard/gui/webviewer.cpp
+++ b/src/librssguard/gui/webviewer.cpp
@@ -178,10 +178,11 @@ void WebViewer::contextMenuEvent(QContextMenuEvent* event) {
   if (menu_data.mediaUrl().isValid() || menu_data.linkUrl().isValid()) {
     QFileIconProvider icon_provider;
     QMenu* menu_ext_tools = new QMenu(tr("Open with external tool"), menu);
+    auto tools = ExternalTool::toolsFromSettings();
 
     menu_ext_tools->setIcon(qApp->icons()->fromTheme(QSL("document-open")));
 
-    for (const ExternalTool& tool : ExternalTool::toolsFromSettings()) {
+    for (const ExternalTool& tool : qAsConst(tools)) {
       QAction* act_tool = new QAction(QFileInfo(tool.executable()).fileName(), menu_ext_tools);
 
       act_tool->setIcon(icon_provider.icon(tool.executable()));
diff --git a/src/librssguard/miscellaneous/feedreader.cpp b/src/librssguard/miscellaneous/feedreader.cpp
index 6c3644374..afd5d61d7 100644
--- a/src/librssguard/miscellaneous/feedreader.cpp
+++ b/src/librssguard/miscellaneous/feedreader.cpp
@@ -8,9 +8,9 @@
 #include "core/feedsproxymodel.h"
 #include "core/messagesmodel.h"
 #include "core/messagesproxymodel.h"
+#include "database/databasequeries.h"
 #include "gui/dialogs/formmessagefiltersmanager.h"
 #include "miscellaneous/application.h"
-#include "database/databasequeries.h"
 #include "miscellaneous/mutex.h"
 #include "services/abstract/cacheforserviceroot.h"
 #include "services/abstract/serviceroot.h"
@@ -164,7 +164,7 @@ void FeedReader::loadSavedMessageFilters() {
   // all feeds.
   m_messageFilters = DatabaseQueries::getMessageFilters(qApp->database()->driver()->connection(metaObject()->className()));
 
-  for (auto* filter : m_messageFilters) {
+  for (auto* filter : qAsConst(m_messageFilters)) {
     filter->setParent(this);
   }
 }
diff --git a/src/librssguard/miscellaneous/iconfactory.cpp b/src/librssguard/miscellaneous/iconfactory.cpp
index e708e14af..1d3e2afbd 100755
--- a/src/librssguard/miscellaneous/iconfactory.cpp
+++ b/src/librssguard/miscellaneous/iconfactory.cpp
@@ -57,14 +57,15 @@ QIcon IconFactory::miscIcon(const QString& name) {
 }
 
 void IconFactory::setupSearchPaths() {
-  QIcon::setThemeSearchPaths(QIcon::themeSearchPaths()
-                             << APP_THEME_PATH
-                             << qApp->applicationDirPath() + QDir::separator() + APP_LOCAL_THEME_FOLDER);
+  auto paths = QIcon::themeSearchPaths();
+
+  paths << APP_THEME_PATH
+        << qApp->applicationDirPath() + QDir::separator() + APP_LOCAL_THEME_FOLDER;
+
+  QIcon::setThemeSearchPaths(paths);
   qDebugNN << LOGSEC_GUI
            << "Available icon theme paths: "
-           << QIcon::themeSearchPaths()
-    .replaceInStrings(QRegularExpression(QSL("^|$")), QSL("\'"))
-    .replaceInStrings(QRegularExpression(QSL("/")), QDir::separator()).join(QSL(", "));
+           << paths;
 }
 
 void IconFactory::setCurrentIconTheme(const QString& theme_name) {
@@ -129,12 +130,13 @@ QStringList IconFactory::installedIconThemes() const {
 
   for (const QString& icon_path : icon_themes_paths) {
     const QDir icon_dir(icon_path);
+    auto icon_paths = icon_dir.entryInfoList(QDir::Filter::Dirs | QDir::Filter::NoDotAndDotDot |
+                                             QDir::Filter::Readable | QDir::Filter::CaseSensitive |
+                                             QDir::Filter::NoSymLinks,
+                                             QDir::SortFlag::Time);
 
     // Iterate all icon themes in this directory.
-    for (const QFileInfo& icon_theme_path : icon_dir.entryInfoList(QDir::Filter::Dirs | QDir::Filter::NoDotAndDotDot |
-                                                                   QDir::Filter::Readable | QDir::Filter::CaseSensitive |
-                                                                   QDir::Filter::NoSymLinks,
-                                                                   QDir::SortFlag::Time)) {
+    for (const QFileInfo& icon_theme_path : qAsConst(icon_paths)) {
       QDir icon_theme_dir = QDir(icon_theme_path.absoluteFilePath());
 
       if (icon_theme_dir.exists(filters_index.at(0))) {
diff --git a/src/librssguard/miscellaneous/localization.cpp b/src/librssguard/miscellaneous/localization.cpp
index b127b54bb..5ec09581e 100644
--- a/src/librssguard/miscellaneous/localization.cpp
+++ b/src/librssguard/miscellaneous/localization.cpp
@@ -72,9 +72,10 @@ QList<Language> Localization::installedLanguages() const {
   QList<Language> languages;
   const QDir file_dir(APP_LANG_PATH);
   QTranslator translator;
+  auto lang_files = file_dir.entryInfoList(QStringList() << QSL("rssguard_*.qm"), QDir::Files, QDir::Name);
 
   // Iterate all found language files.
-  for (const QFileInfo& file : file_dir.entryInfoList(QStringList() << "rssguard_*.qm", QDir::Files, QDir::Name)) {
+  for (const QFileInfo& file : qAsConst(lang_files)) {
     if (translator.load(file.absoluteFilePath())) {
       Language new_language;
 
diff --git a/src/librssguard/miscellaneous/textfactory.cpp b/src/librssguard/miscellaneous/textfactory.cpp
index 803908d65..e2a8f96f2 100755
--- a/src/librssguard/miscellaneous/textfactory.cpp
+++ b/src/librssguard/miscellaneous/textfactory.cpp
@@ -86,7 +86,7 @@ QDateTime TextFactory::parseDateTime(const QString& date_time) {
                            << QSL("-hhmm") << QSL("+hh") << QSL("-hh");
 
   // Iterate over patterns and check if input date/time matches the pattern.
-  for (const QString& pattern : date_patterns) {
+  for (const QString& pattern : qAsConst(date_patterns)) {
     dt = locale.toDateTime(input_date.left(pattern.size()), pattern);
 
     if (dt.isValid()) {
@@ -97,7 +97,7 @@ QDateTime TextFactory::parseDateTime(const QString& date_time) {
       if (input_date.size() >= TIMEZONE_OFFSET_LIMIT) {
         QString offset_sanitized = input_date.mid(pattern.size()).replace(QL1S(" "), QString());
 
-        for (const QString& pattern_t : timezone_offset_patterns) {
+        for (const QString& pattern_t : qAsConst(timezone_offset_patterns)) {
           time_zone_offset = QTime::fromString(offset_sanitized.left(pattern_t.size()), pattern_t);
 
           if (time_zone_offset.isValid()) {
diff --git a/src/librssguard/miscellaneous/textfactory.h b/src/librssguard/miscellaneous/textfactory.h
index c091f50e9..54fc5ae4d 100755
--- a/src/librssguard/miscellaneous/textfactory.h
+++ b/src/librssguard/miscellaneous/textfactory.h
@@ -22,7 +22,7 @@ class TextFactory {
 
     // Tries to parse input textual date/time representation.
     // Returns invalid date/time if processing fails.
-    // NOTE: This method tries to always return time in UTC+00:00.
+    // NOTE: This method tries to always return time in UTC.
     static QDateTime parseDateTime(const QString& date_time);
 
     // Converts 1970-epoch miliseconds to date/time.
diff --git a/src/librssguard/network-web/adblock/adblockaddsubscriptiondialog.cpp b/src/librssguard/network-web/adblock/adblockaddsubscriptiondialog.cpp
index a01f03b32..89a6d63b1 100644
--- a/src/librssguard/network-web/adblock/adblockaddsubscriptiondialog.cpp
+++ b/src/librssguard/network-web/adblock/adblockaddsubscriptiondialog.cpp
@@ -28,16 +28,12 @@ AdBlockAddSubscriptionDialog::AdBlockAddSubscriptionDialog(QWidget* parent)
   : QDialog(parent), m_ui(new Ui::AdBlockAddSubscriptionDialog) {
   m_ui->setupUi(this);
   m_knownSubscriptions
-    << Subscription(QSL("EasyList"),
-                    QSL(ADBLOCK_EASYLIST_URL))
-    << Subscription(QSL("EasyPrivacy"),
-                  QSL("https://easylist.to/easylist/easyprivacy.txt"))
-    << Subscription(QSL("EasyPrivacy Tracking Protection List"),
-                  QSL("https://easylist-downloads.adblockplus.org/easyprivacy.tpl"))
-    << Subscription(QSL("Adblock Warning Removal List"),
-                  QSL("https://easylist-downloads.adblockplus.org/antiadblockfilters.txt"));
+    << Subscription(QSL("EasyList"), QSL(ADBLOCK_EASYLIST_URL))
+    << Subscription(QSL("EasyPrivacy"), QSL("https://easylist.to/easylist/easyprivacy.txt"))
+    << Subscription(QSL("EasyPrivacy Tracking Protection List"), QSL("https://easylist-downloads.adblockplus.org/easyprivacy.tpl"))
+    << Subscription(QSL("Adblock Warning Removal List"), QSL("https://easylist-downloads.adblockplus.org/antiadblockfilters.txt"));
 
-  for (const Subscription& subscription : m_knownSubscriptions) {
+  for (const Subscription& subscription : qAsConst(m_knownSubscriptions)) {
     m_ui->m_cmbPresets->addItem(subscription.m_title);
   }
 
diff --git a/src/librssguard/network-web/adblock/adblockdialog.cpp b/src/librssguard/network-web/adblock/adblockdialog.cpp
index 529625119..5c37b0b14 100644
--- a/src/librssguard/network-web/adblock/adblockdialog.cpp
+++ b/src/librssguard/network-web/adblock/adblockdialog.cpp
@@ -159,7 +159,9 @@ void AdBlockDialog::load() {
     return;
   }
 
-  for (AdBlockSubscription* subscription : m_manager->subscriptions()) {
+  auto subs = m_manager->subscriptions();
+
+  for (AdBlockSubscription* subscription : qAsConst(subs)) {
     auto* tree = new AdBlockTreeWidget(subscription, m_ui->m_tabSubscriptions);
 
     m_ui->m_tabSubscriptions->addTab(tree, subscription->title());
diff --git a/src/librssguard/network-web/adblock/adblockmanager.cpp b/src/librssguard/network-web/adblock/adblockmanager.cpp
index ada89197b..5ddfee207 100644
--- a/src/librssguard/network-web/adblock/adblockmanager.cpp
+++ b/src/librssguard/network-web/adblock/adblockmanager.cpp
@@ -178,7 +178,9 @@ void AdBlockManager::load(bool initial_load) {
       QDir().mkpath(storedListsPath());
     }
 
-    for (const QString& subscription_file_name : adblock_dir.entryList(QStringList("*.txt"), QDir::Files)) {
+    auto subs_files = adblock_dir.entryList({ QSL("*.txt") }, QDir::Filter::Files);
+
+    for (const QString& subscription_file_name : qAsConst(subs_files)) {
       if (subscription_file_name == ADBLOCK_CUSTOMLIST_NAME) {
         continue;
       }
@@ -216,7 +218,7 @@ void AdBlockManager::load(bool initial_load) {
     m_subscriptions.append(custom_list);
 
     // Load all subscriptions.
-    for (AdBlockSubscription* subscription : m_subscriptions) {
+    for (AdBlockSubscription* subscription : qAsConst(m_subscriptions)) {
       subscription->loadSubscription(m_disabledRules);
       connect(subscription, &AdBlockSubscription::subscriptionChanged, this, &AdBlockManager::updateMatcher);
     }
@@ -244,7 +246,7 @@ void AdBlockManager::updateMatcher() {
 }
 
 void AdBlockManager::updateAllSubscriptions() {
-  for (AdBlockSubscription* subscription : m_subscriptions) {
+  for (AdBlockSubscription* subscription : qAsConst(m_subscriptions)) {
     subscription->updateSubscription();
   }
 
@@ -256,7 +258,7 @@ void AdBlockManager::save() {
     return;
   }
 
-  for (AdBlockSubscription* subscription : m_subscriptions) {
+  for (AdBlockSubscription* subscription : qAsConst(m_subscriptions)) {
     subscription->saveSubscription();
   }
 
diff --git a/src/librssguard/network-web/adblock/adblockmatcher.cpp b/src/librssguard/network-web/adblock/adblockmatcher.cpp
index 90e157700..71edec90f 100644
--- a/src/librssguard/network-web/adblock/adblockmatcher.cpp
+++ b/src/librssguard/network-web/adblock/adblockmatcher.cpp
@@ -133,9 +133,12 @@ void AdBlockMatcher::update() {
   clear();
   QHash<QString, const AdBlockRule*> cssRulesHash;
   QVector<const AdBlockRule*> exceptionCssRules;
+  auto subs = m_manager->subscriptions();
 
-  for (AdBlockSubscription* subscription : m_manager->subscriptions()) {
-    for (const AdBlockRule* rule : subscription->allRules()) {
+  for (AdBlockSubscription* subscription : qAsConst(subs)) {
+    auto rls = subscription->allRules();
+
+    for (const AdBlockRule* rule : qAsConst(rls)) {
       // Don't add internally disabled rules to cache.
       if (rule->isInternalDisabled()) {
         continue;
diff --git a/src/librssguard/network-web/adblock/adblocksubscription.cpp b/src/librssguard/network-web/adblock/adblocksubscription.cpp
index 132181b8d..9ab410de0 100644
--- a/src/librssguard/network-web/adblock/adblocksubscription.cpp
+++ b/src/librssguard/network-web/adblock/adblocksubscription.cpp
@@ -329,7 +329,7 @@ void AdBlockCustomList::saveSubscription() {
   textStream << "Url: " << url().toString() << QL1C('\n');
   textStream << "[Adblock Plus 1.1.1]" << QL1C('\n');
 
-  for (const AdBlockRule* rule : m_rules) {
+  for (const AdBlockRule* rule : qAsConst(m_rules)) {
     textStream << rule->filter() << QL1C('\n');
   }
 
diff --git a/src/librssguard/network-web/downloader.cpp b/src/librssguard/network-web/downloader.cpp
index 8b7b17684..7e20768d2 100644
--- a/src/librssguard/network-web/downloader.cpp
+++ b/src/librssguard/network-web/downloader.cpp
@@ -171,17 +171,18 @@ QList<HttpResponse> Downloader::decodeMultipartAnswer(QNetworkReply* reply) {
                                             start_of_body - start_of_headers).replace(QRegularExpression(QSL("[\\n\\r]+")),
                                                                                       QSL("\n"));
 
-    for (const QString& header_line : headers.split(QL1C('\n'),
+    auto header_lines = headers.split(QL1C('\n'),
 #if QT_VERSION >= 0x050F00 // Qt >= 5.15.0
-                                                    Qt::SplitBehaviorFlags::SkipEmptyParts)) {
+                                      Qt::SplitBehaviorFlags::SkipEmptyParts);
 #else
-                                                    QString::SplitBehavior::SkipEmptyParts)) {
+                                      QString::SplitBehavior::SkipEmptyParts);
 #endif
+
+    for (const QString& header_line : qAsConst(header_lines)) {
       int index_colon = header_line.indexOf(QL1C(':'));
 
       if (index_colon > 0) {
-        new_part.appendHeader(header_line.mid(0, index_colon),
-                              header_line.mid(index_colon + 2));
+        new_part.appendHeader(header_line.mid(0, index_colon), header_line.mid(index_colon + 2));
       }
     }
 
diff --git a/src/librssguard/network-web/networkurlinterceptor.cpp b/src/librssguard/network-web/networkurlinterceptor.cpp
index d5cc2809a..6d668cdc8 100644
--- a/src/librssguard/network-web/networkurlinterceptor.cpp
+++ b/src/librssguard/network-web/networkurlinterceptor.cpp
@@ -33,7 +33,7 @@ void NetworkUrlInterceptor::interceptRequest(QWebEngineUrlRequestInfo& info) {
 
   // NOTE: Here we can add custom headers for each webengine request, for example "User-Agent".
 
-  for (UrlInterceptor* interceptor : m_interceptors) {
+  for (UrlInterceptor* interceptor : qAsConst(m_interceptors)) {
     interceptor->interceptRequest(info);
   }
 }
diff --git a/src/librssguard/network-web/webfactory.cpp b/src/librssguard/network-web/webfactory.cpp
index 20f388cc5..782d91b54 100644
--- a/src/librssguard/network-web/webfactory.cpp
+++ b/src/librssguard/network-web/webfactory.cpp
@@ -156,7 +156,7 @@ QString WebFactory::unescapeHtml(const QString& html) {
           }
           else {
             // Failed to convert to number, leave intact.
-            output.append(html.mid(pos, pos_end - pos + 1));
+            output.append(html.midRef(pos, pos_end - pos + 1));
           }
 
           pos = pos_end + 1;
diff --git a/src/librssguard/network-web/webfactory.h b/src/librssguard/network-web/webfactory.h
index 0d80fc1e8..a0eaae396 100644
--- a/src/librssguard/network-web/webfactory.h
+++ b/src/librssguard/network-web/webfactory.h
@@ -41,7 +41,6 @@ class WebFactory : public QObject {
     NetworkUrlInterceptor* urlIinterceptor();
 #endif
 
-  public slots:
     void updateProxy();
     bool openUrlInExternalBrowser(const QString& url) const;
     bool sendMessageViaEmail(const Message& message);
diff --git a/src/librssguard/services/abstract/accountcheckmodel.cpp b/src/librssguard/services/abstract/accountcheckmodel.cpp
index 117a235f6..736aff3fd 100644
--- a/src/librssguard/services/abstract/accountcheckmodel.cpp
+++ b/src/librssguard/services/abstract/accountcheckmodel.cpp
@@ -42,7 +42,9 @@ void AccountCheckModel::setRootItem(RootItem* root_item, bool delete_previous_ro
 
 void AccountCheckModel::checkAllItems() {
   if (m_rootItem != nullptr) {
-    for (RootItem* root_child : m_rootItem->childItems()) {
+    auto chi = m_rootItem->childItems();
+
+    for (RootItem* root_child : qAsConst(chi)) {
       if (root_child->kind() == RootItem::Kind::Feed || root_child->kind() == RootItem::Kind::Category) {
         setItemChecked(root_child, Qt::Checked);
       }
@@ -52,7 +54,9 @@ void AccountCheckModel::checkAllItems() {
 
 void AccountCheckModel::uncheckAllItems() {
   if (m_rootItem != nullptr) {
-    for (RootItem* root_child : m_rootItem->childItems()) {
+    auto chi = m_rootItem->childItems();
+
+    for (RootItem* root_child : qAsConst(chi)) {
       if (root_child->kind() == RootItem::Kind::Feed || root_child->kind() == RootItem::Kind::Category) {
         setData(indexForItem(root_child), Qt::Unchecked, Qt::CheckStateRole);
       }
@@ -161,7 +165,7 @@ QVariant AccountCheckModel::data(const QModelIndex& index, int role) const {
 
   RootItem* item = itemForIndex(index);
 
-  if (role == Qt::CheckStateRole) {
+  if (role == Qt::ItemDataRole::CheckStateRole) {
     if (m_checkStates.contains(item)) {
       return m_checkStates.value(item);
     }
@@ -169,15 +173,13 @@ QVariant AccountCheckModel::data(const QModelIndex& index, int role) const {
       return static_cast<int>(Qt::Unchecked);
     }
   }
-  else if (role == Qt::DecorationRole) {
-    auto ic = item->icon();
-
+  else if (role == Qt::ItemDataRole::DecorationRole) {
     return item->data(0, Qt::ItemDataRole::DecorationRole);
   }
-  else if (role == Qt::EditRole) {
+  else if (role == Qt::ItemDataRole::EditRole) {
     return QVariant::fromValue(item);
   }
-  else if (role == Qt::DisplayRole) {
+  else if (role == Qt::ItemDataRole::DisplayRole) {
     switch (item->kind()) {
       case RootItem::Kind::Category:
         return QVariant(item->data(index.column(), role).toString() + QSL(" ") + tr("(category)"));
@@ -213,7 +215,9 @@ bool AccountCheckModel::setData(const QModelIndex& index, const QVariant& value,
     }
 
     // Set new data for all descendants of this actual item.
-    for (RootItem* child : item->childItems()) {
+    auto chi = item->childItems();
+
+    for (RootItem* child : qAsConst(chi)) {
       setData(indexForItem(child), value, Qt::CheckStateRole);
     }
 
@@ -230,8 +234,9 @@ bool AccountCheckModel::setData(const QModelIndex& index, const QVariant& value,
       // Check children of this new parent item.
       bool all_checked = true;
       bool all_unchecked = true;
+      auto chi = item->childItems();
 
-      for (RootItem* child_of_parent : item->childItems()) {
+      for (RootItem* child_of_parent : qAsConst(chi)) {
         if (m_checkStates.contains(child_of_parent)) {
           all_checked &= m_checkStates[child_of_parent] == Qt::CheckState::Checked;
           all_unchecked &= m_checkStates[child_of_parent] == Qt::CheckState::Unchecked;
diff --git a/src/librssguard/services/abstract/category.cpp b/src/librssguard/services/abstract/category.cpp
index 841903e41..5bb8368fd 100644
--- a/src/librssguard/services/abstract/category.cpp
+++ b/src/librssguard/services/abstract/category.cpp
@@ -2,8 +2,8 @@
 
 #include "services/abstract/category.h"
 
-#include "miscellaneous/application.h"
 #include "database/databasequeries.h"
+#include "miscellaneous/application.h"
 #include "miscellaneous/iconfactory.h"
 #include "miscellaneous/textfactory.h"
 #include "services/abstract/cacheforserviceroot.h"
@@ -20,8 +20,9 @@ Category::Category(const Category& other) : RootItem(other) {
 
 void Category::updateCounts(bool including_total_count) {
   QList<Feed*> feeds;
+  auto str = getSubTree();
 
-  for (RootItem* child : getSubTree()) {
+  for (RootItem* child : qAsConst(str)) {
     if (child->kind() == RootItem::Kind::Feed) {
       feeds.append(child->toFeed());
     }
diff --git a/src/librssguard/services/abstract/feed.cpp b/src/librssguard/services/abstract/feed.cpp
index 7c77af75b..a7e98a905 100755
--- a/src/librssguard/services/abstract/feed.cpp
+++ b/src/librssguard/services/abstract/feed.cpp
@@ -97,7 +97,7 @@ void Feed::setCountOfAllMessages(int count_all_messages) {
 }
 
 void Feed::setCountOfUnreadMessages(int count_unread_messages) {
-  if (status() == Status::NewMessages && count_unread_messages < countOfUnreadMessages()) {
+  if (status() == Status::NewMessages && count_unread_messages < m_unreadCount) {
     setStatus(Status::Normal);
   }
 
diff --git a/src/librssguard/services/abstract/rootitem.cpp b/src/librssguard/services/abstract/rootitem.cpp
index 73ea2926d..e371f0af5 100644
--- a/src/librssguard/services/abstract/rootitem.cpp
+++ b/src/librssguard/services/abstract/rootitem.cpp
@@ -74,7 +74,7 @@ bool RootItem::deleteViaGui() {
 bool RootItem::markAsReadUnread(ReadStatus status) {
   bool result = true;
 
-  for (RootItem* child : m_childItems) {
+  for (RootItem* child : qAsConst(m_childItems)) {
     result &= child->markAsReadUnread(status);
   }
 
@@ -84,7 +84,7 @@ bool RootItem::markAsReadUnread(ReadStatus status) {
 QList<Message> RootItem::undeletedMessages() const {
   QList<Message> messages;
 
-  for (RootItem* child : m_childItems) {
+  for (RootItem* child : qAsConst(m_childItems)) {
     if (child->kind() != Kind::Bin && child->kind() != Kind::Labels && child->kind() != Kind::Label) {
       messages.append(child->undeletedMessages());
     }
@@ -96,7 +96,7 @@ QList<Message> RootItem::undeletedMessages() const {
 bool RootItem::cleanMessages(bool clear_only_read) {
   bool result = true;
 
-  for (RootItem* child : m_childItems) {
+  for (RootItem* child : qAsConst(m_childItems)) {
     if (child->kind() != RootItem::Kind::Bin) {
       result &= child->cleanMessages(clear_only_read);
     }
@@ -106,7 +106,7 @@ bool RootItem::cleanMessages(bool clear_only_read) {
 }
 
 void RootItem::updateCounts(bool including_total_count) {
-  for (RootItem* child : m_childItems) {
+  for (RootItem* child : qAsConst(m_childItems)) {
     child->updateCounts(including_total_count);
   }
 }
diff --git a/src/librssguard/services/abstract/serviceroot.cpp b/src/librssguard/services/abstract/serviceroot.cpp
index 0d3618bf0..15d02d083 100644
--- a/src/librssguard/services/abstract/serviceroot.cpp
+++ b/src/librssguard/services/abstract/serviceroot.cpp
@@ -120,8 +120,9 @@ void ServiceRoot::stop() {}
 
 void ServiceRoot::updateCounts(bool including_total_count) {
   QList<Feed*> feeds;
+  auto str = getSubTree();
 
-  for (RootItem* child : getSubTree()) {
+  for (RootItem* child : qAsConst(str)) {
     if (child->kind() == RootItem::Kind::Feed) {
       feeds.append(child->toFeed());
     }
@@ -194,7 +195,9 @@ void ServiceRoot::removeOldAccountFromDatabase(bool including_messages) {
 }
 
 void ServiceRoot::cleanAllItemsFromModel() {
-  for (RootItem* top_level_item : childItems()) {
+  auto chi = childItems();
+
+  for (RootItem* top_level_item : qAsConst(chi)) {
     if (top_level_item->kind() != RootItem::Kind::Bin &&
         top_level_item->kind() != RootItem::Kind::Important &&
         top_level_item->kind() != RootItem::Kind::Labels) {
@@ -203,7 +206,9 @@ void ServiceRoot::cleanAllItemsFromModel() {
   }
 
   if (labelsNode() != nullptr) {
-    for (RootItem* lbl : labelsNode()->childItems()) {
+    auto lbl_chi = labelsNode()->childItems();
+
+    for (RootItem* lbl : qAsConst(lbl_chi)) {
       requestItemRemoval(lbl);
     }
   }
@@ -218,10 +223,8 @@ void ServiceRoot::appendCommonNodes() {
     appendChild(importantNode());
   }
 
-  if (labelsNode() != nullptr) {
-    if (!childItems().contains(labelsNode())) {
-      appendChild(labelsNode());
-    }
+  if (labelsNode() != nullptr && !childItems().contains(labelsNode())) {
+    appendChild(labelsNode());
   }
 }
 
@@ -338,10 +341,13 @@ void ServiceRoot::addNewCategory(RootItem* selected_item) {
 
 QMap<QString, QVariantMap> ServiceRoot::storeCustomFeedsData() {
   QMap<QString, QVariantMap> custom_data;
+  auto str = getSubTreeFeeds();
 
-  for (const Feed* feed : getSubTreeFeeds()) {
+  for (const Feed* feed : qAsConst(str)) {
     QVariantMap feed_custom_data;
 
+    // TODO: This could potentially call Feed::customDatabaseData() and append it
+    // to this map and also subsequently restore.
     feed_custom_data.insert(QSL("auto_update_interval"), feed->autoUpdateInitialInterval());
     feed_custom_data.insert(QSL("auto_update_type"), int(feed->autoUpdateType()));
     feed_custom_data.insert(QSL("msg_filters"), QVariant::fromValue(feed->messageFilters()));
@@ -412,7 +418,9 @@ void ServiceRoot::syncIn() {
     removeLeftOverMessageFilterAssignments();
     removeLeftOverMessageLabelAssignments();
 
-    for (RootItem* top_level_item : new_tree->childItems()) {
+    auto chi = new_tree->childItems();
+
+    for (RootItem* top_level_item : qAsConst(chi)) {
       if (top_level_item->kind() != Kind::Labels) {
         top_level_item->setParent(nullptr);
         requestItemReassignment(top_level_item, this);
@@ -420,7 +428,9 @@ void ServiceRoot::syncIn() {
       else {
         // It seems that some labels got synced-in.
         if (labelsNode() != nullptr) {
-          for (RootItem* new_lbl : top_level_item->childItems()) {
+          auto lbl_chi = top_level_item->childItems();
+
+          for (RootItem* new_lbl : qAsConst(lbl_chi)) {
             new_lbl->setParent(nullptr);
             requestItemReassignment(new_lbl, labelsNode());
           }
@@ -464,7 +474,9 @@ QStringList ServiceRoot::customIDSOfMessagesForItem(RootItem* item) {
     switch (item->kind()) {
       case RootItem::Kind::Labels:
       case RootItem::Kind::Category: {
-        for (RootItem* child : item->childItems()) {
+        auto chi = item->childItems();
+
+        for (RootItem* child : qAsConst(chi)) {
           list.append(customIDSOfMessagesForItem(child));
         }
 
diff --git a/src/librssguard/services/abstract/serviceroot.h b/src/librssguard/services/abstract/serviceroot.h
index 801089f18..0d4601649 100644
--- a/src/librssguard/services/abstract/serviceroot.h
+++ b/src/librssguard/services/abstract/serviceroot.h
@@ -40,13 +40,14 @@ class ServiceRoot : public RootItem {
     virtual ~ServiceRoot();
 
     // These methods bellow are part of "interface".
+    RecycleBin* recycleBin() const;
+    ImportantNode* importantNode() const;
+    LabelsNode* labelsNode() const;
+
     virtual void updateCounts(bool including_total_count);
     virtual bool canBeDeleted() const;
     virtual bool deleteViaGui();
     virtual bool markAsReadUnread(ReadStatus status);
-    virtual RecycleBin* recycleBin() const;
-    virtual ImportantNode* importantNode() const;
-    virtual LabelsNode* labelsNode() const;
     virtual bool downloadAttachmentOnMyOwn(const QUrl& url) const;
     virtual QList<Message> undeletedMessages() const;
     virtual bool supportsFeedAdding() const;
diff --git a/src/librssguard/services/feedly/feedlynetwork.cpp b/src/librssguard/services/feedly/feedlynetwork.cpp
index e5f34ff74..8e92ee3e9 100755
--- a/src/librssguard/services/feedly/feedlynetwork.cpp
+++ b/src/librssguard/services/feedly/feedlynetwork.cpp
@@ -231,7 +231,9 @@ QList<Message> FeedlyNetwork::decodeStreamContents(const QByteArray& stream_cont
 
   continuation = json.object()["continuation"].toString();
 
-  for (const QJsonValue& entry : json.object()["items"].toArray()) {
+  auto items = json.object()["items"].toArray();
+
+  for (const QJsonValue& entry : qAsConst(items)) {
     const QJsonObject& entry_obj = entry.toObject();
     Message message;
 
@@ -255,7 +257,9 @@ QList<Message> FeedlyNetwork::decodeStreamContents(const QByteArray& stream_cont
       message.m_url = entry_obj["canonical"].toObject()["href"].toString();
     }
 
-    for (const QJsonValue& enc : entry_obj["enclosure"].toArray()) {
+    auto enclosures = entry_obj["enclosure"].toArray();
+
+    for (const QJsonValue& enc : qAsConst(enclosures)) {
       const QJsonObject& enc_obj = enc.toObject();
       const QString& enc_href = enc_obj["href"].toString();
 
@@ -266,7 +270,9 @@ QList<Message> FeedlyNetwork::decodeStreamContents(const QByteArray& stream_cont
       }
     }
 
-    for (const QJsonValue& tag : entry_obj["tags"].toArray()) {
+    auto tags = entry_obj["tags"].toArray();
+
+    for (const QJsonValue& tag : qAsConst(tags)) {
       const QJsonObject& tag_obj = tag.toObject();
       const QString& tag_id = tag_obj["id"].toString();
 
@@ -332,15 +338,18 @@ RootItem* FeedlyNetwork::decodeCollections(const QByteArray& json, bool obtain_i
   QJsonDocument doc = QJsonDocument::fromJson(json);
   auto* parent = new RootItem();
   QList<QString> used_feeds;
+  auto coll = doc.array();
 
-  for (const QJsonValue& cat : doc.array()) {
+  for (const QJsonValue& cat : qAsConst(coll)) {
     QJsonObject cat_obj = cat.toObject();
     auto* category = new Category(parent);
 
     category->setTitle(cat_obj["label"].toString());
     category->setCustomId(cat_obj["id"].toString());
 
-    for (const QJsonValue& fee : cat["feeds"].toArray()) {
+    auto feeds = cat["feeds"].toArray();
+
+    for (const QJsonValue& fee : qAsConst(feeds)) {
       QJsonObject fee_obj = fee.toObject();
 
       if (used_feeds.contains(fee_obj["id"].toString())) {
@@ -446,8 +455,9 @@ QList<RootItem*> FeedlyNetwork::tags() {
 
   QJsonDocument json = QJsonDocument::fromJson(output);
   QList<RootItem*> lbls;
+  auto tags = json.array();
 
-  for (const QJsonValue& tag : json.array()) {
+  for (const QJsonValue& tag : qAsConst(tags)) {
     const QJsonObject& tag_obj = tag.toObject();
     QString name_id = tag_obj["id"].toString();
 
diff --git a/src/librssguard/services/feedly/gui/feedlyaccountdetails.cpp b/src/librssguard/services/feedly/gui/feedlyaccountdetails.cpp
index ddd807ba8..12c6d3aca 100755
--- a/src/librssguard/services/feedly/gui/feedlyaccountdetails.cpp
+++ b/src/librssguard/services/feedly/gui/feedlyaccountdetails.cpp
@@ -130,7 +130,9 @@ void FeedlyAccountDetails::performTest(const QNetworkProxy& custom_proxy) {
   factory.setDeveloperAccessToken(m_ui.m_txtDeveloperAccessToken->lineEdit()->text());
 
   try {
-    m_ui.m_txtUsername->lineEdit()->setText(factory.profile(custom_proxy)["email"].toString());
+    auto prof = factory.profile(custom_proxy);
+
+    m_ui.m_txtUsername->lineEdit()->setText(prof["email"].toString());
     m_ui.m_lblTestResult->setStatus(WidgetWithStatus::StatusType::Ok,
                                     tr("Login was successful."),
                                     tr("Access granted."));