Zitat von "vicente.botet" <vicente.botet@wanadoo.fr>:
what do you think about the basic_* and alias approach? is that feasible for your library?
Yes I think so.
great. Bob, what about your library?
Does TransactionManager::begin_transaction makes a transaction or registers the stack allocated one?
undefined. the basic_transaction_manager implementation does neither(see below).
unspecified TM::begin_transaction() ; what about void TM::begin_transaction(TM::transaction&) ;
I considered that, but this approach has some problems(transaction must be DefaultConstructible, deferred "construction", ...) and the current approach is as powerful. note that using a return value does not mean that the transaction has to be CopyConstructible, the only requirement is that TransactionManager::transaction(txmgr.begin_transaction()) is a valid expression. you can for example do the following and still comply with the concept: class transaction_manager{ struct construct_tag{}; public: construct_tag begin_transaction(){ return construct_tag(); } class transaction : noncopyable{ explicit transaction(construct_tag); } }; in case you asked this question because of dynamic allocation, there is not a single allocation caused e.g. by the following code (if the accessed object is already loaded from disk): transaction tx; pinned_loc<pers_type const> l; std::cerr << l->value; tx.commit(); whatever you store in ResourceManager::transaction of your resource manager resides on the user´s stack.
I would like to see something in the line of
namespace this_transaction { transaction* current(); ... }
or
namespace current_transaction { ... }
what´s your point of this? that you´d like to have a simple syntax to obtain the current transaction? a namespace doesn´t provide the type of the transaction manager configured by the user. the syntax to obtain the global transaction currently is: TxMgr::active().active_transaction() as in, obtain the active transaction manager, and then obtain the active transaction from the manager. the return value is of type (TxMgr::transaction &).