Introduced a helper class for performing transactions

Avoids having to remember to call rollbackTransaction and makes
transactions exception-safe (since the destructor of PerformTransaction
will be called when an exception is thrown).

2 files changed, 42 insertions, 0 deletions

diff --git a/src/dal/dataprovider.cpp b/src/dal/dataprovider.cpp
index 370741c..f6bcbdf 100644
--- a/src/dal/dataprovider.cpp
+++ b/src/dal/dataprovider.cpp
@@ -25,6 +25,26 @@
 namespace dal
 {
 
+PerformTransaction::PerformTransaction(DataProvider *dataProvider)
+    : mDataProvider(dataProvider)
+    , mCommitted(false)
+{
+    mDataProvider->beginTransaction();
+}
+
+PerformTransaction::~PerformTransaction()
+{
+    if (!mCommitted)
+        mDataProvider->rollbackTransaction();
+}
+
+void PerformTransaction::commit()
+{
+    mDataProvider->commitTransaction();
+    mCommitted = true;
+}
+
+
 /**
  * Constructor.
  */
diff --git a/src/dal/dataprovider.h b/src/dal/dataprovider.h
index 7ea15a7..1764ef1 100644
--- a/src/dal/dataprovider.h
+++ b/src/dal/dataprovider.h
@@ -30,6 +30,8 @@
 namespace dal
 {
 
+class DataProvider;
+
 /**
  * Enumeration type for the database backends.
  */
@@ -39,6 +41,26 @@ typedef enum {
     DB_BKEND_POSTGRESQL
 } DbBackends;
 
+/**
+ * Begins a transaction on a given data provider. When the transaction is
+ * complete, commit() should be called. When the destructor is called before
+ * commit() is called, the transaction is rolled back.
+ *
+ * This avoids having to remember to call rollback in a lot of places, and
+ * makes exception handling easier.
+ */
+class PerformTransaction
+{
+public:
+    PerformTransaction(DataProvider *dataProvider);
+    ~PerformTransaction();
+
+    void commit();
+
+private:
+    DataProvider *mDataProvider;
+    bool mCommitted;
+};
 
 /**
  * An abstract data provider.