fix subsribe to settings changes

settingslistner.cpp

@@ -7,26 +7,46 @@
 
 #include "isettings.h"
 #include "settingslistner.h"
+#include "params.h"
 
 namespace QuasarAppUtils {
 
 SettingsListner::SettingsListner() {
-
-    auto settings = ISettings::instance();
-    if (settings) {
-
-        auto listner = [this](QString key, QVariant val){
-            this->handleSettingsChanged(key, val);
-        };
-
-        _listnerConnection = QObject::connect(settings,
-                                              &ISettings::valueChanged,
-                                              listner);
-    }
 }
 
 SettingsListner::~SettingsListner() {
     QObject::disconnect(_listnerConnection);
 }
 
+bool SettingsListner::handleSettings() {
+
+    auto settings = ISettings::instance();
+    if (!settings) {
+        Params::log("Settings object is not initialised!"
+                    "please invoke ISettings::init before subscribe",
+                    Error);
+        return false;
+    }
+
+    auto listner = [this](QString key, QVariant val){
+        this->handleSettingsChanged(key, val);
+    };
+
+    QObject * thiz = dynamic_cast<QObject*>(this);
+
+    if (!thiz) {
+        Params::log("Object that use the SettingsListner should be QObject."
+                    "The handleSettingsChanged method will not invoked when settings has changed",
+                    Error);
+        return false;
+    }
+
+    _listnerConnection = thiz->connect(settings,
+                                       &ISettings::valueChanged,
+                                       thiz, listner,
+                                       Qt::QueuedConnection);
+
+    return true;
+}
+
 }

settingslistner.h

@@ -24,6 +24,12 @@ namespace QuasarAppUtils {
  *
  * @code{cpp}
  *  class MyClass : protected QuasarAppUtils::SettingsListner {
+ *
+ *  public:
+ *      MyClass(){
+ *          handleSettings();
+ *      }
+ *
  *  protected:
  *      void handleSettingsChanged(const QString& key, const QVariant& value) override {
  *
@@ -34,6 +40,9 @@ namespace QuasarAppUtils {
  *
  *  };
  * @endcode
+ *
+ * @warning For correctly working this handler you should be create a class that inherit of the QObject class else
+ *  the SettingsListner::handleSettingsChanged will nit invoked when settings has changed.
  * @see ISettings
  */
 class QUASARAPPSHARED_EXPORT SettingsListner
@@ -44,6 +53,13 @@ public:
 
 protected:
 
+    /**
+     * @brief handleSettings This method subscribe this class to listning settings changes.
+     * @return true if subscribed successful else false.
+     * @see SettingsListner::handleSettingsChanged
+     */
+    bool handleSettings();
+
     /**
      * @brief handleSettingsChanged This method will be invoked when settings of application has bean changed.
      * @param key This is key of a changed settings.