【深入学习iOS开发（五）】Archive（归档）

Archive（归档）

Archives provide a means to convert objects and values into an architecture-independent stream of bytes that preserves the identity of and the relationships between the objects and values.

1、归档与解档

Archive

RootObject

[NSKeyedArchiver archiveRootObject:[contentTextField text] toFile:[self archiveFilePath]];

Keyed

NSString *content = [contentTextField text];
NSMutableData *data = [NSMutableData data];
NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];
[archiver encodeObject:content forKey:@"content"];
[archiver finishEncoding];
[data writeToFile:[self archiveFilePath] atomically:YES];

Unarchive

Root Object

[contentLabel setText:[NSKeyedUnarchiver unarchiveObjectWithFile:[self archiveFilePath]]];

Keyed

NSData *data = [NSData dataWithContentsOfFile:[self archiveFilePath]];
NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];
[contentLabel setText:[unarchiver decodeObjectForKey:@"content"]];
[unarchiver finishDecoding];

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2、NSCoding Protocol

为了支持编码（encoding）和解码（decoding），类需要实现NSCoding Protocol。

以类Person为例：

Person.h

#import <Foundation/Foundation.h>

#define PERSON_KEY_FIRSTNAME @"FIRSTNAME"
#define PERSON_KEY_LASTNAME @"LASTNAME"
#define PERSON_KEY_HEIGHT @"HEIGHT"

@interface Person : NSObject <NSCoding>

@property (nonatomic, retain) NSString *firstName;
@property (nonatomic, retain) NSString *lastName;
@property (nonatomic, assign) float height;

@end

Person.m

#import "Person.h"

@implementation Person

@synthesize firstName, lastName, height;

- (void)encodeWithCoder:(NSCoder *)aCoder {
    [aCoder encodeObject:self.firstName forKey:PERSON_KEY_FIRSTNAME];
    [aCoder encodeObject:self.lastName forKey:PERSON_KEY_LASTNAME];
    [aCoder encodeFloat:self.height forKey:PERSON_KEY_HEIGHT];
}

- (id)initWithCoder:(NSCoder *)aDecoder {
    self = [super init];
    if (self != nil) {
        self.firstName = [aDecoder decodeObjectForKey:PERSON_KEY_FIRSTNAME];
        self.lastName = [aDecoder decodeObjectForKey:PERSON_KEY_LASTNAME];
        self.height = [aDecoder decodeFloatForKey:PERSON_KEY_HEIGHT];
    }
    return self;
}

@end

参考：https://developer.apple.com/library/ios/#documentation/Cocoa/Conceptual/Archiving/Archiving.html