iOS 基礎類解析 - NSData

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NSData Class Reference

Inherits from	NSObject
Conforms to	NSCopying NSMutableCopying NSSecureCoding NSObject (NSObject)
Framework	/System/Library/Frameworks/Foundation.framework
Availability	Available in iOS 2.0 and later.
Declared in	NSData.h
Companion guides	Binary Data Programming Guide Property List Programming Guide
Related sample code	AdvancedURLConnectionsCryptoExerciseEADemoMVCNetworkingSimpleURLConnections

Overview

NSData and its mutable subclass NSMutableData provide data objects, object-oriented wrappers for byte buffers. Data objects let simple allocated buffers (that is, data with no embedded pointers) take on the behavior of Foundation objects.

NSData creates static data objects, and NSMutableData creates dynamic data objects. NSData and NSMutableData are typically used for data storage and are also useful in Distributed Objects applications, where data contained in data objects can be copied or moved between applications.

The size of the data is subject to a theoretical limit of about 8 ExaBytes (in practice, the limit should not be a factor).

NSData is “toll-free bridged” with its Core Foundation counterpart, CFDataRef. See “Toll-Free Bridging” for more information on toll-free bridging.

TasksCreating Data Objects

• + data
• + dataWithBytes:length:
• + dataWithBytesNoCopy:length:
• + dataWithBytesNoCopy:length:freeWhenDone:
• + dataWithContentsOfFile:
• + dataWithContentsOfFile:options:error:
• + dataWithContentsOfURL:
• + dataWithContentsOfURL:options:error:
• + dataWithData:
• – initWithBase64EncodedData:options:
• – initWithBase64EncodedString:options:
• – initWithBytes:length:
• – initWithBytesNoCopy:length:
• – initWithBytesNoCopy:length:deallocator:
• – initWithBytesNoCopy:length:freeWhenDone:
• – initWithContentsOfFile:
• – initWithContentsOfFile:options:error:
• – initWithContentsOfURL:
• – initWithContentsOfURL:options:error:
• – initWithData:
• – initWithBase64Encoding: Deprecated in iOS 7.0
• + dataWithContentsOfMappedFile: Deprecated in iOS 5.0
• – initWithContentsOfMappedFile: Deprecated in iOS 5.0

Accessing Data

• – bytes
• – description
• – enumerateByteRangesUsingBlock:
• – getBytes:length:
• – getBytes:range:
• – subdataWithRange:
• – rangeOfData:options:range:
• – getBytes: Deprecated in iOS 4.0

Base-64 Encoding

• – base64EncodedDataWithOptions:
• – base64EncodedStringWithOptions:
• – base64Encoding Deprecated in iOS 7.0

Testing Data

• – isEqualToData:
• – length

Storing Data

• – writeToFile:atomically:
• – writeToFile:options:error:
• – writeToURL:atomically:
• – writeToURL:options:error:

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