对象归档是将对象归档以文件的形式保存到磁盘中(也称为序列化，持久化)，使用的时候读取该文件的保存路径读取文件的内容（也称为解档，反序列化）
主要涉及两个类：NSKeyedArichiver、NSKeyedUnarchiver
两个协议NSCoding的2个方法:
- (void)encodeWithCoder:
- (id)initWithCoder:
可以接着(一)的例子，新建文件，subclass of NSObject, 实现NSCoding协议
新建文件.h
#import <Foundation/Foundation.h> @interface BSLFourLines : NSObject<NSCoding> @property (copy, nonatomic) NSString *field1;
@property (copy, nonatomic) NSString *field2;
@property (copy, nonatomic) NSString *field3;
@property (copy, nonatomic) NSString *field4; @end
新建文件.m
#import "BSLFourLines.h"
#define kField1Key @"Field1"
#define kField2Key @"Field2"
#define kField3Key @"Field3"
#define kField4Key @"Field4" @implementation BSLFourLines
@synthesize field1,field2,field3,field4; #pragma mark NSCoding
//以keyValue形式对基本数据类型Encoding
- (void)encodeWithCoder:(NSCoder *)aCoder{
[aCoder encodeObject:field1 forKey:kField1Key];
[aCoder encodeObject:field2 forKey:kField2Key];
[aCoder encodeObject:field3 forKey:kField3Key];
[aCoder encodeObject:field4 forKey:kField4Key];
} //以keyValue形式对基本数据类型Decoding，返回数据模型本身
- (id)initWithCoder:(NSCoder *)aDecoder{
if (self = [super init]) {
field1 = [aDecoder decodeObjectForKey:kField1Key];
field2 = [aDecoder decodeObjectForKey:kField2Key];
field3 = [aDecoder decodeObjectForKey:kField3Key];
field4 = [aDecoder decodeObjectForKey:kField4Key];
}
return self;
}
现在转到XXViewController.m在#import下方添加
#import "BSLFourLines.h"
#define kFilename2 @"archive"
#define kDataKey @"Data"
改动后的方法内容
- (void)viewDidLoad
{
[super viewDidLoad];
NSString *filePath = [self dataFilePath];
//检查数据文件是否存在，如果存在就用此文件内容实例化数组
if ([[NSFileManager defaultManager] fileExistsAtPath:filePath]) { NSData *data = [[NSMutableData alloc] initWithContentsOfFile:[self dataFilePath]];
NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];
BSLFourLines *fourLines = [unarchiver decodeObjectForKey:kDataKey];
[unarchiver finishDecoding]; field1.text = fourLines.field1;
field2.text = fourLines.field2;
field3.text = fourLines.field3;
field4.text = fourLines.field4;
}
//通知
UIApplication *app = [UIApplication sharedApplication];
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(applicationWillResignActive:) name:UIApplicationWillResignActiveNotification object:app];
}
- (void)applicationWillResignActive:(NSNotification *)notification{
BSLFourLines *fourLines = [[BSLFourLines alloc] init];
fourLines.field1 = field1.text;
fourLines.field2 = field2.text;
fourLines.field3 = field3.text;
fourLines.field4 = field4.text;
NSMutableData *data = [[NSMutableData alloc] init];
NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];
[archiver encodeObject:fourLines forKey:kDataKey];
[archiver finishEncoding];
[data writeToFile:[self dataFilePath] atomically:YES];
}
如果需要对自定义的类进行copy的话，需要在自定义类实现<NSCoding>协议
自定义类的实现文件里添加下列方法
- (id)copyWithZone:(NSZone *)zone{
BSLFourLines *copy = [[[self class] allocWithZone:zone] init];
copy.field1 = [self.field1 copyWithZone:zone];
copy.field2 = [self.field2 copyWithZone:zone];
copy.field3 = [self.field3 copyWithZone:zone];
copy.field4 = [self.field4 copyWithZone:zone];
return copy;
}