ios专题 －归档保存数据

关键类：NSKeyedArchiver  与  NSKeyedUnarchiver

采用归档的形式来保存数据，该数据对象需要遵守NSCoding协议，并且该对象对应的类必须提供encodeWithCoder:和initWithCoder:方法。前一个方法告诉系统怎么对对象进行编码，而后一个方法则是告诉系统怎么对对象进行解码

例子：

LQAnimal.h

#import <UIKit/UIKit.h>

@interface LQAnimal : NSObject <NSCoding>

@property (strong) NSString *animalType;

@end

LQAnimal.m

#import "LQAnimal.h"

@implementation LQAnimal

@synthesize animalType = _animalType;

/*
 *从未归档数据中，初始化对象
 */
- (id) initWithCoder:(NSCoder *) theCoder
{
    LQAnimal *what = [[LQAnimal alloc] init];
    
    what.animalType = [theCoder decodeObjectForKey:@"type"];
    
    return what;
}

/*
 *归档时，编码
 */
- (void) encodeWithCoder:(NSCoder *)theCoder
{
    [theCoder encodeObject:self.animalType forKey:@"type"];
}

@end

    NSString *path = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask,YES)[0];
    NSString *detailPath = [NSString stringWithFormat:@"%@/animal.txt",path];
    LQAnimal *animal = [[LQAnimal alloc] init];
    //animal.animalType = @" little fat sheep ";
    animal.animalType = @" big fat sheep ";
    BOOL isOK = [NSKeyedArchiver archiveRootObject:animal toFile:detailPath];
    if (isOK) {
        NSLog(@"save object success!");
        LQAnimal *getAnimal = [NSKeyedUnarchiver unarchiveObjectWithFile:detailPath];
        NSLog(@"APP get animal type:%@", getAnimal.animalType);
    } else{
        NSLog(@"save object fail！");
    }

执行结果：

2014-01-03 19:12:22.144 Objc[696:c07] save object success!
2014-01-03 19:12:25.601 Objc[696:c07] APP get animal type: big fat sheep

我执行后，也检查过了animal.txt文本内容，发现系乱码。。

bplist00‘
T$topX$objectsX$versionY$archiver—TrootÄ
§    
U$null“
V$classTtypeÄÄ_ big fat sheep “X$classesZ$classname¢XLQAnimalXNSObjectXLQAnimal
܆_NSKeyedArchiver(25:<AGLSXZ
s|áäìú•™

º

这种模式只适合少量配置数据的存储。优点就系够简单。起码比sqlite简单很多。