Passing by reference [C++], [Qt]

I wrote something like this: ``` class Storage { public: Storage(); QString key() const; int value() const; void add_item(QString&,int); private: QMap<QString,int>* my_map_; }; void Storage::add_item(QString& key,int value)//------HERE IS THE SLOT FOR ADDING { *my_map_[key] = value; } ``` and when I'm trying to add item to `QMap` by: ``` class Dialog : public QDialog { Q_OBJECT public: Dialog(QWidget* = 0); public slots: void add_item() { strg_->add_item(ui->lineEdit->text(),ui->spinBox->value());//---HERE I'M "PASSING" TWO OBJECTS: QString AND int ui->lineEdit->clear(); } private: Ui::Dialog* ui; Storage* strg_; }; ``` I'm getting error: ``` error: no matching function for call to 'Storage::add_item(QString, int) note: candidates are: void Storage::add_item(QString&, int) ``` How am I suppose to send `QString` by ref. other then I do it now? Thank you.