Pass arguemnts by const reference

src/base/torrentfilter.cpp

@@ -49,14 +49,14 @@ TorrentFilter::TorrentFilter()
 {
 }
 
-TorrentFilter::TorrentFilter(Type type, QStringSet hashSet, QString category)
+TorrentFilter::TorrentFilter(const Type type, const QStringSet &hashSet, const QString &category)
     : m_type(type)
     , m_category(category)
     , m_hashSet(hashSet)
 {
 }
 
-TorrentFilter::TorrentFilter(QString filter, QStringSet hashSet, QString category)
+TorrentFilter::TorrentFilter(const QString &filter, const QStringSet &hashSet, const QString &category)
     : m_type(All)
     , m_category(category)
     , m_hashSet(hashSet)

src/base/torrentfilter.h

@@ -72,8 +72,8 @@ public:
 
     TorrentFilter();
     // category: pass empty string for "no category" or null string (QString()) for "any category"
-    TorrentFilter(Type type, QStringSet hashSet = AnyHash, QString category = AnyCategory);
+    TorrentFilter(const Type type, const QStringSet &hashSet = AnyHash, const QString &category = AnyCategory);
-    TorrentFilter(QString filter, QStringSet hashSet = AnyHash, QString category = AnyCategory);
+    TorrentFilter(const QString &filter, const QStringSet &hashSet = AnyHash, const QString &category = AnyCategory);
 
     bool setType(Type type);
     bool setTypeByName(const QString &filter);