MBFileReadOperation Class Reference

Inherits from	NSOperation
Declared in	MBFilesystemOperations.h

Overview

An NSOperation subclass that can be used to read file data.

MBFileReadOperation instances are added to NSOperationQueues to be performed, and the MBFileReadOperationDelegate associated with the operation is notified on the main thread when the operation completes successfully or fails.

The MBFilesystemOperationQueue singleton is available as a convenience for performing filesystem operations such as this.

Object lifecycle

`+ operationForReadingFromFile:delegate:`

Creates a new MBFileReadOperation instance that can be used to read the contents of the file specified.

+ (nonnull instancetype)operationForReadingFromFile:(nonnull NSString *)path delegate:(nonnull NSObject<MBFileReadOperationDelegate> *)delegate

Parameters

`path`	The filesystem path of the file to be read by the returned operation.
`delegate`	The delegate that will be notified upon completion of the returned operation.

Return Value

The newly-created MBFileReadOperation instance.

Declared In

MBFilesystemOperations.h

`– initForFilePath:delegate:`

Initializes the receiver so it can be used to read from the specified file.

- (nonnull instancetype)initForFilePath:(nonnull NSString *)path delegate:(nonnull NSObject<MBFileReadOperationDelegate> *)delegate

Parameters

`path`	The filesystem path of the file to be read by the receiver.
`delegate`	The delegate that will be notified upon completion of the operation.

Return Value

The receiver.

Declared In

MBFilesystemOperations.h

Getting information about the operation

`filePath`

Returns the filesystem path of the file to be read by the operation.

@property (nonnull, nonatomic, readonly) NSString *filePath

Declared In

MBFilesystemOperations.h

`delegate`

Returns the MBFileReadOperationDelegate that will be notified when the operation completes.

@property (nonnull, nonatomic, readonly) NSObject<MBFileReadOperationDelegate> *delegate

Declared In

MBFilesystemOperations.h

Subclassing hooks

`– readObjectFromFile:error:`

Called internally to read the file and convert its data into an object.

- (nullable id)readObjectFromFile:(nonnull NSString *)path error:(NSErrorPtrPtr)errPtr

Parameters

`path`	The filesystem path of the file to read.
`errPtr`	If this method returns `nil` and this parameter is non-`nil`, `*errPtr` will be updated to point to an `NSError` instance containing further information about the error.

Return Value

The object that was read from the file.

Discussion

The default implementation returns an NSData instance. Subclasses may override this method to return other types of objects.

Declared In

MBFilesystemOperations.h

`– readCompletedWithObject:`

Called internally when readObjectFromFile:error: completes successfully.

- (void)readCompletedWithObject:(nonnull id)readObj

Parameters

`readObj`	The object that was read from the filesystem, as returned by `readObjectFromFile:error:`.

Discussion

Warning: Subclasses may override this method to perform additional work when the operation completes, but must call super to ensure that the operation’s delegate is notified.

Declared In

MBFilesystemOperations.h

`– readFailedWithError:`

Called internally when readObjectFromFile:error: fails.

- (void)readFailedWithError:(nonnull NSError *)err

Parameters

`err`	The error describing the reason that `readObjectFromFile:error:` failed.

Discussion

Warning: Subclasses may override this method to perform additional work when the operation completes, but must call super to ensure that the operation’s delegate is notified.

Declared In

MBFilesystemOperations.h