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1 是一种序列化方式，先将归档对象序列化为一个文件，然后再通过反归档将数据恢复到对象中。
条件：该对象的类必须实现NSCoding协议，而且每个成员变量应该是基本数据类型或都是实现NSCoding协议的某个类的实例。
归档类NSKeyedArchiver 反归档类NSKeyedUnarchiver NSData类提供了读取数据文件的方法
方法：＋dataWithContentsOfFile：
＋dataWithContentsOfFile：options：指定读取数据选项error：
－initWithContentsOfFile：/options:error:
-writeToFile:atomically:若文件不存在在这时候创建一个
-writeToFile:options:error:
2 归档：封装NSData对象－封装NSKeyedArchiver对象－编码－完成编码－写入文件
- (void)createEditableCopyOfDatabaseIfNeeded {
NSFileManager *fileManager = [NSFileManager defaultManager];
NSString *writableDBPath = [self applicationDocumentsDirectoryFile];
BOOL dbexits = [fileManager fileExistsAtPath:writableDBPath];
if (!dbexits) {
NSString *path = [self applicationDocumentsDirectoryFile];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
NSDate *date1 = [dateFormatter dateFromString:@"2010-08-04 16:01:03"];
Note* note1 = [[Note alloc] init];
note1.date = date1;
note1.content = @"Welcome to MyNote.";
NSMutableArray* array = [[NSMutableArray alloc] init]；
[array addObject:note1];
NSMutableData * theData = [NSMutableData data];
NSKeyedArchiver * archiver = [[NSKeyedArchiver alloc]
initForWritingWithMutableData:theData];
[archiver encodeObject:array forKey:ARCHIVE_KEY];里面的Note对象必须是实现NSCoding协议
[archiver finishEncoding];
[theData writeToFile:path atomically:YES];
}
}
- (NSString *)applicationDocumentsDirectoryFile {
NSString *documentDirectory = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
NSString *path = [documentDirectory stringByAppendingPathComponent:FILE_NAME];
return path;
}
Note类必须实现NSCoding协议：
-(void)encodeWithCoder:(NSCoder *)aCoder {编码
[aCoder encodeObject:_date forKey:@"date"];
[aCoder encodeObject:_content forKey:@"content"];
}
-(id)initWithCoder:(NSCoder *)aDecoder {反编码
self.date = [aDecoder decodeObjectForKey:@"date"];
self.content = [aDecoder decodeObjectForKey:@"content"];
return self;
}
3 反归档：查询
//查询所有数据方法
-(NSMutableArray*) findAll
{
NSString *path = [self applicationDocumentsDirectoryFile];
NSMutableArray *listData = [[NSMutableArray alloc] init];
NSData * theData =[NSData dataWithContentsOfFile:path];
if([theData length] > 0) {判断归档对象是否有数据
NSKeyedUnarchiver * archiver = [[NSKeyedUnarchiver alloc]
initForReadingWithData:theData];
listData = [archiver decodeObjectForKey:ARCHIVE_KEY];
[archiver finishDecoding];
}
return listData;
}
//按照主键查询数据方法
-(Note*) findById:(Note*)model
{
NSString *path = [self applicationDocumentsDirectoryFile];
NSMutableArray *listData = [[NSMutableArray alloc] init];
NSData * theData =[NSData dataWithContentsOfFile:path];
if([theData length] > 0) {
NSKeyedUnarchiver * archiver = [[NSKeyedUnarchiver alloc]
initForReadingWithData:theData];
listData = [archiver decodeObjectForKey:ARCHIVE_KEY];
[archiver finishDecoding];
for (Note* note in listData) {
//比较日期主键是否相等
if ([note.date isEqualToDate:model.date]){
return note;
}
}
}
return nil;
}
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原文地址：http://www.cnblogs.com/haugezi/p/4821124.html
