MBConcurrentReadWriteCoordinator Class Reference
| Inherits from | NSObject |
|---|---|
| Declared in | MBConcurrentReadWriteCoordinator.h |
Overview
The MBConcurrentReadWriteCoordinator uses Grand Central Dispatch to provide
an efficient mechanism for enforcing orderly read/write access to a shared
resource.
The coordinator ensures that concurrent access to the shared resource follows these rules:
A read operation never executes at the same time as a write operation
Multiple read operations may execute simultaneously
Only one write operation may be executing at any given time
Read operations occur synchronously
Write operations occur asynchronously
Because of the underlying GCD mechanism used, when used properly, the implementation ensures serial order with respect to reads and writes. That is, a call to perform a read operation will always return the results of the most-recently enqueued write operation.
– read:
Synchronously executes the read operation contained in the passed-in block. If a writer is executing when this method is called, the calling thread will be blocked until writing finishes. Multiple readers may execute simultaneously.
- (void)read:(nonnull void ( ^ ) ( ))readOperationParameters
readOperation |
The read operation. |
|---|
Declared In
MBConcurrentReadWriteCoordinator.h
– enqueueWrite:
Enqueues a write operation for eventual execution. The passed-in block will be executed only when there are no other readers or writers.
- (void)enqueueWrite:(nonnull void ( ^ ) ( ))writeOperationParameters
writeOperation |
The write operation. |
|---|
Discussion
Any calls to the receiver’s read: method that are issued after a call
to enqueueWrite: are guaranteed to execute after its writeOperation
block finishes executing. This ensures that reads and writes can occur in
a predictable order.
Declared In
MBConcurrentReadWriteCoordinator.h