TxSessionGuard Class Reference
Namespace | ohm::flip |
Declared in | ohm/flip/TxSessionGuard.h |
See Also |
Overview
The TxSessionGuard class implements a convenient class to manage transaction as well as a guard to detect common errors when manipulating transactions.
Usually, every custom Flip classes implemented by the client should have a TxSessionGuard member.
The following sections will only document the public API.
Partial Class Diagram
Methods Overview
Constructor
Manipulating
State
Methods
TxSessionGuard constructor
Constructs a TxSessionGuard and bind it to a document.
TxSessionGuard (DocumentBase & document); |
prepare_record
Prepares the undo system to start to record the transaction if needed.
Important:If used, it must be called before the transaction is started with start .
void prepare_record (Scribe & scribe); |
If the transaction does not need to be recorded by the undo system, this function must not be called.
start
Starts the transaction if possible. Returns true if the transaction was successfully started, false otherwise.
bool start (); |
A transaction cannot be started if the document has already an ongoing transaction. However a transaction maybe joined : see can_join below.
commit
Commits the transaction. The transaction must have been started with start before. If the transaction was not started, then this will trigger an assert .
void commit (); |
When a transaction is commited, it is sent to the server for validation and broadcast to the other clients.
revert
Reverts the transaction. The transaction must have been started with start before. If the transaction was not started, then this will trigger an assert .
void revert (); |
When a transaction is reverted, the model is automatically rollbacked, and a call to the observer is issued if needed.
In particular, reverting a transaction does not send anything to the server.
can_start
Returns true if a transaction was not already started, false otherwise.
bool can_start (); |
is_started
Returns true if a transaction was already started on this, false otherwise.
bool can_start (); |
This function only applies to this session guard. The function might return false while a transaction might be opened at the document level.
can_join
Returns true if a transaction was already started on this, or at the document level, false otherwise.
bool can_join (); |
Joining a transaction allows objects to fill the current transaction without the need to start a transaction themselves. This is rarely used, but is handy for concurrent manipulation such as, for example, scrolling in a document while the user drags an object, where the drag is part of the transaction.