Do not keep a copy of database’s connection name

Since i only plan to use a single connection, i can use QtSql’s default
connection name.

According to the documentation, i have to make sure that no query or
database object is open when i remove the database.  I now use C++
scopes for that, but i need to have a QString declared outside of it to
get the default connection’s name.

src/database.cpp

@@ -6,7 +6,6 @@
 Database::Database(QObject *parent)
     : QObject{parent}
     , m_pool{}
-    , m_connectionName{"main"}
 {
     m_pool.setMaxThreadCount(1);
     m_pool.setExpiryTimeout(-1);
@@ -15,28 +14,36 @@ Database::Database(QObject *parent)
 QFuture<void> Database::open(const QString &user, const QString &password)
 {
     return QtConcurrent::run(&m_pool, [this, user, password]() {
-        QSqlDatabase db = QSqlDatabase::addDatabase("QPSQL", m_connectionName);
+        QString errorMessage;
+        QString connectionName;
+        {
+            QSqlDatabase db = QSqlDatabase::addDatabase("QPSQL");
             db.setConnectOptions("service=camper; options=-csearch_path=camper,public");
             if (db.open(user, password)) {
                 emit opened();
-        } else {
-            const QString errorMessage(db.lastError().text());
-            db = QSqlDatabase(); // Otherwise removeDatabase complains is still being used.
-            QSqlDatabase::removeDatabase(m_connectionName);
-            emit errorOcurred(errorMessage);
+                return;
             }
+            errorMessage = db.lastError().text();
+            connectionName = db.connectionName();
+        }
+        QSqlDatabase::removeDatabase(connectionName);
+        emit errorOcurred(errorMessage);
     });
 }
 
 QFuture<void> Database::close()
 {
     return QtConcurrent::run(&m_pool, [this]() {
-        QSqlDatabase db = QSqlDatabase::database(m_connectionName);
+        QString connectionName;
+        {
+            QSqlDatabase db = QSqlDatabase::database();
             if (!db.isValid()) {
                 return;
             }
+            connectionName = db.connectionName();
             db.close();
-        QSqlDatabase::removeDatabase(m_connectionName);
+        }
+        QSqlDatabase::removeDatabase(connectionName);
         emit closed();
     });
 }

src/database.h

@@ -25,7 +25,6 @@ signals:
 
 private:
     QThreadPool m_pool;
-    QString m_connectionName;
 };
 
 #endif // DATABASE_H