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)[];
    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—Trootħ
U$null“
V$classTtypeÄÄ_ big fat sheep “X$classesZ$classname¢XLQAnimalXNSObjectXLQAnimal܆_NSKeyedArchiver(:<AGLSXZ\ns|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。