四种数据持久化方式总目录
2.归档
归档(archiving)也是指另一种形式的序列化,但是它是任何对象都可以实现的更常规的类型。尽管我们对归档的使用没有严格要求,我们一般要实现两个协议NSCoding协议和NSCoping协议。
NSCoding协议声明了2个方法:一个是将对象编码到归档中,另一个是对归档的解码来恢复我们之前归档的对象,使用方法与NSUserDefaults相似也可以用KVC对对象和原生数据类型(如int和float)进行编码和解码。
①对单个对象进行归档
使用NSKeyedArichiver进行归档、NSKeyedUnarchiver进行接档,这种方式会在写入、读出数据之前对数据进行序列化、反序列化操作。
归档:
NSString *homeDictionary = NSHomeDirectory();//获取根目录
NSString *homePath = [homeDictionary stringByAppendingPathComponent:@"atany.archiver"];//添加储存的文件名
BOOL flag = [NSKeyedArchiver archiveRootObject:@”归档” toFile:homePath];//归档一个字符串
这种方式可以对字符串、数字等进行归档,当然也可以对NSArray与NSDictionary进行归档。返回值Flag标志着是否归档成功,YES为成功,NO为失败。
接档:
[NSKeyedUnarchiver unarchiveObjectWithFile:homePath]
使用NSKeyedUnarchiver进行接档(反序列化)。
**这种归档的方式存在一个缺点:只能把一个对象归档进一个文件中。
②对多个对象进行归档
同样是使用NSKeyedArchiver进行归档,不同的是同时归档多个对象,这里我们举例放入了一个CGPoint点、字符串、整数(当然很多类型都可以的,例如UIImage、float等等),使用encodeXXX方法进行归档,最后通过writeToFile方法写入文件。
归档:写入数据
//准备数据
CGPoint point = CGPointMake(1.0, 2.0);
NSString *info = @"坐标原点";
NSInteger value = 10;
NSString *multiHomePath = [NSHomeDirectory() stringByAppendingPathComponent:@"multi.archiver"];
NSMutableData *data = [[NSMutableData alloc]init];
NSKeyedArchiver *archvier = [[NSKeyedArchiver alloc]initForWritingWithMutableData:data];
//对多个对象进行归档
[archvier encodeCGPoint:point forKey:@"kPoint"];
[archvier encodeObject:info forKey:@"kInfo"];
[archvier encodeInteger:value forKey:@"kValue"];
[archvier finishEncoding];
[data writeToFile:multiHomePath atomically:YES];
接档:从路径中获得数据构造NSKeyedUnarchiver实例,使用decodeXXXForKey方法获得文件中的对象。
NSMutableData *dataR = [[NSMutableData alloc]initWithContentsOfFile:multiHomePath];
NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc]initForReadingWithData:dateR];
CGPoint pointR = [unarchiver decodeCGPointForKey:@"kPoint"];
NSString *infoR = [unarchiver decodeObjectForKey:@"kInfo"];
NSInteger valueR = [unarchiver decodeIntegerForKey:@"kValue"];
[unarchiver finishDecoding];
NSLog(@"%f,%f,%@,%d",pointR.x,pointR.y,infoR,valueR);
**可以看出对多个对象进行归档还是挺方便的,这里又出现一个问题,这里的对象都是基本类型数据。
③对自定义对象进行归档
//这是我建立的两个类和一个APPDelegate类,归档的操作在ViewController中操作,Person是要被归档的类
**Person.h
@interface Person : NSObject
@property (copy,nonatomic) NSString *name;
@property (copy,nonatomic) NSString *age;
@property (copy,nonatomic) NSString *phone;
@end
**Person.m
@implementation Person
- (void)encodeWithCoder:(NSCoder *)aCoder{
[aCoder encodeObject:_name forKey:@"name"];
[aCoder encodeObject:_age forKey:@"age"];
[aCoder encodeObject:_phone forKey:@"phone"];
}
- (instancetype)initWithCoder:(NSCoder *)aDecoder{
if (self = [super init]) {
_name = [aDecoder decodeObjectForKey:@"name"];
_age = [aDecoder decodeObjectForKey:@"age"];
_phone = [aDecoder decodeObjectForKey:@"phone"];
}
return self;
}
-(id)copyWithZone:(NSZone *)zone
{
Person *copy = [[[self class] allocWithZone:zone] init];
copy.name = [self.name copyWithZone:zone];
copy.age = self.age;
copy.phone = self.phone;
return copy;
}
@end
**ViewController.m
#import "ViewController.h"
#import "Person.h"
#define KEY @"person"
@interface ViewController ()
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
Person *per = [[Person alloc] init];
per.name = @"阿杰";
per.age = @"30";
per.phone = @"1234567";
//存储路径
NSArray *path = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *demoPath = [path objectAtIndex:0];
NSString *spath = [demoPath stringByAppendingPathComponent:@"Singel.archiver"];
//归档
NSMutableData *data = [NSMutableData new];
NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];
[archiver encodeObject:per forKey:KEY];
[archiver finishEncoding];
Boolean result = [data writeToFile:spath atomically:YES];
//拷贝(没有用per2这个类)
Person *per2 = [per copy];
if (result) {
NSLog(@"归档成功:%@",spath);
}
//接档
NSMutableData *uData = [[NSMutableData alloc] initWithContentsOfFile:spath];
NSKeyedUnarchiver *uarchier = [[NSKeyedUnarchiver alloc] initForReadingWithData:uData];
Person *uper = [uarchier decodeObjectForKey:KEY];
NSLog(@"%@",uper.name);
NSLog(@"%@",uper.age);
NSLog(@"%@",uper.phone);
}
@end
Person实现了三个委托方法1)encodeWithCoder: 2)initWithCoder: 3)copyWithZone:
1)encodeWithCoder
Encodes the receiverusing a given archiver
通过一个给定的archiver把消息接收者进行编码。
当接收到encodeObject消息的时候,类终端encodeWithCoder方法被调用。
2)initWithCoder
Returns an objectinitialized from data in a given unarchiver. (required)
从一个给定unarchiver的数据中返回一个初始化对象。
3)copyWithZone
Returnsa new instance that’s a copy of the receiver
返回消息接收者的一个复制的新实例。