/Users/apple/Library/Application Support/iPhone Simulator/6.0/Applications

 /Users/用户名/资源库/Application Support/iPhone Simulator/6.1/Applications

 NSString *home = NSHomeDirectory();

NSString *home = NSHomeDirectory();
NSString *documents = [home stringByAppendingPathComponent:@"Documents"];
// 不建议采用，因为新版本的操作系统可能会修改目录名

// NSUserDomainMask 代表从用户文件夹下找  
// YES 代表展开路径中的波浪字符“~”
NSArray *array = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, NO);
// 在iOS中，只有一个目录跟传入的参数匹配，所以这个集合里面只有一个元素
NSString *documents = [array objectAtIndex:0];

 NSString *tmp= NSTemporaryDirectory();

// 将数据封装成字典 
NSMutableDictionary *dict = [NSMutableDictionary dictionary];
[dict setObject:@"15013141314" forKey:@"phone"];
[dict setObject:@"27" forKey:@"age"];
// 将字典持久化到Documents/stu.plist文件中
[dict writeToFile:path atomically:YES];

// 读取Documents/stu.plist的内容，实例化NSDictionary
NSDictionary *dict = [NSDictionary dictionaryWithContentsOfFile:path];
NSLog(@"phone:%@", [dict objectForKey:@"phone"]);
NSLog(@"age:%@", [dict objectForKey:@"age"]);

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
[defaults setObject:@"Cat" forKey:@"username"];
[defaults setFloat:14.0f forKey:@"text_size"];
[defaults setBool:YES forKey:@"auto_login"];

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSString *username = [defaults stringForKey:@"username"];
float textSize = [defaults floatForKey:@"text_size"];
BOOL autoLogin = [defaults boolForKey:@"auto_login"];

 [defaults synchornize];

NSString *path = [NSString stringWithFormat:@"Documents/array.archive"];
NSArray *array = [NSArray arrayWithObjects:@"a",@"b",nil];
[NSKeyedArchiver archiveRootObject:array toFile:path];

 NSArray *array = [NSKeyedUnarchiver unarchiveObjectWithFile:path];

@interface Person : NSObject <NSCoding>
@property(nonatomic,copy) NSString *name;
@property(nonatomic,assign) int age;
@property(nonatomic,assign) float height;@end

 @implementation Person
-(void)encodeWithCoder:(NSCoder*)encoder{  
 [encoder encodeObject:self.name forKey:@"name"];  
 [encoder encodeInt:self.age forKey:@"age"];  
 [encoder encodeFloat:self.height forKey:@"height"];
}
-(id)initWithCoder:(NSCoder*)decoder {  
 self.name= [decoder decodeObjectForKey:@"name"];  
 self.age= [decoder decodeIntForKey:@"age"];  
 self.height= [decoder decodeFloatForKey:@"height"];  
 return self;
}

 // 归档(编码)
 Person *person = [[Person alloc] init];
 person.name = @"JN";
 person.age = 22;
 person.height = 1.63f;
 [NSKeyedArchiver archiveRootObject:person toFile:path];

 // 恢复(解码)
 Person *person = [NSKeyedUnarchiver unarchiveObjectWithFile:path];
@end

// 新建一块可变数据区
NSMutableData *data = [NSMutableData data];
// 将数据区连接到一个NSKeyedArchiver对象
NSKeyedArchiver *archiver = [[[NSKeyedArchiver alloc] initForWritingWithMutableData:data] autorelease];
// 开始存档对象，存档的数据都会存储到NSMutableData中
[archiver encodeObject:person1 forKey:@"person1"];
[archiver encodeObject:person2 forKey:@"person2"];
// 存档完毕(一定要调用这个方法)
[archiver finishEncoding];
// 将存档的数据写入文件
[data writeToFile:path atomically:YES];

// 从文件中读取数据
NSData *data = [NSData dataWithContentsOfFile:path];
// 根据数据，解析成一个NSKeyedUnarchiver对象
NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];
Person *person1 = [unarchiver decodeObjectForKey:@"person1"];
Person *person2 = [unarchiver decodeObjectForKey:@"person2"];
// 恢复完毕[unarchiver finishDecoding];

// 临时存储person1的数据
NSData *data = [NSKeyedArchiver archivedDataWithRootObject:person1];
// 解析data，生成一个新的Person对象
Student *person2 = [NSKeyedUnarchiver unarchiveObjectWithData:data];
// 分别打印内存地址
NSLog(@"person1:%@", person1); // person1:0x8d3ed10>
NSLog(@"person2:%@", person2); // person2:0x8d3e2f0>

create table if not exists t_student (id integer, name text, age inetger, score real) ;

drop table if exists t_student;

insert into t_student (name, age) values ('JN', 22) ;

pupdate t_student set name = 'jack', age = 20 ;

delete from t_student;

// 将t_student表中年龄大于10 并且 姓名不等于jack的记录，年龄都改为 5 
update t_student set age = 5 where age > 10 and name != ‘jack' ; 
// 删除t_student表中年龄小于等于10 或者 年龄大于30的记录 
delete from t_student where age <= 10 or age > 30 ;

select * from t_student where age > 10 ; // 条件查询条件语句:

// path为：~/Documents/person.db
sqlite3 *db;int result = sqlite3_open([path UTF8String], &db);

char *errorMsg; // 用来存储错误信息
char *sql = "create table if not exists t_person(id integer primary key autoincrement, name text, age integer);";
int result = sqlite3_exec(db, sql, NULL, NULL, &errorMsg);

1.打开数据库
int sqlite3_open(  
const char *filename,  // 数据库的文件路径  
sqlite3 **ppDb     // 数据库实例
);
2.执行任何SQL语句
int sqlite3_exec(  
sqlite3*,        // 一个打开的数据库实例  
const char *sql,              // 需要执行的SQL语句  
int (*callback)(void*,int,char**,char**), // SQL语句执行完毕后的回调  
void *,                  // 回调函数的第1个参数  
char **errmsg               // 错误信息
);
3.检查SQL语句的合法性（查询前的准备）
int sqlite3_prepare_v2(
  sqlite3 *db,      // 数据库实例  
const char *zSql,    // 需要检查的SQL语句  
int nByte,       // SQL语句的最大字节长度  
sqlite3_stmt **ppStmt, // sqlite3_stmt实例，用来获得数据库数据  
const char **pzTail
);
4.查询一行数据
int sqlite3_step(
sqlite3_stmt*); // 如果查询到一行数据，就会返回SQLITE_ROW
5.利用stmt获得某一字段的值（字段的下标从0开始）
double sqlite3_column_double(sqlite3_stmt*, int iCol); // 浮点数据
int sqlite3_column_int(sqlite3_stmt*, int iCol); // 整型数据
sqlite3_int64 sqlite3_column_int64(sqlite3_stmt*, int iCol); // 长整型数据
const void *sqlite3_column_blob(sqlite3_stmt*, int iCol); // 二进制文本数据
const unsigned char *sqlite3_column_text(sqlite3_stmt*, int iCol); // 字符串数据

// 从应用程序包中加载模型文件 
NSManagedObjectModel *model = [NSManagedObjectModel mergedModelFromBundles:nil];
// 传入模型，初始化
NSPersistentStoreCoordinator NSPersistentStoreCoordinator *psc = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:model];
// 构建SQLite文件路径 
NSString *docs = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];NSURL *url = [NSURL fileURLWithPath:[docs stringByAppendingPathComponent:@"person.data"]];
// 添加持久化存储库，这里使用SQLite作为存储库 
NSError *error = nil;
NSPersistentStore *store = [psc addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:url options:nil error:&error];
if (store == nil) { // 直接抛异常  
    [NSException raise:@"添加数据库错误" format:@"%@", [error localizedDescription]];
}
// 初始化上下文，设置persistentStoreCoordinator属性 
NSManagedObjectContext *context = [[NSManagedObjectContext alloc] init];context.persistentStoreCoordinator = psc;
// 用完之后，还是要[context release];
/*持久化存储库的类型：NSSQLiteStoreType SQLite数据库 
NSBinaryStoreType 二进制平面文件 
NSInMemoryStoreType 内存库，无法永久保存数据 
虽然这3种类型的性能从速度上来说都差不多，但从数据模型中保留下来的信息却不一样
在几乎所有的情景中，都应该采用默认设置，使用SQLite作为持久化存储库
*/

// 传入上下文，创建一个Person实体对象 
NSManagedObject *person = [NSEntityDescription insertNewObjectForEntityForName:@"Person" inManagedObjectContext:context];
// 设置简单属性 
[person setValue:@"JN" forKey:@"name"];
[person setValue:[NSNumber numberWithInt:22] forKey:@"age"];
// 传入上下文，创建一个Card实体对象 
NSManagedObject *card = [NSEntityDescription insertNewObjectForEntityForName:@"Card" inManagedObjectContext:context];
[card setValue:@"447640819" forKey:@"no"];
// 设置Person和Card之间的关联关系 
[person setValue:card forKey:@"card"];
 // 利用上下文对象，将数据同步到持久化存储库 
NSError *error = nil;BOOL success = [context save:&error];
if (!success) { 
    [NSException raise:@"访问数据库错误" format:@"%@", [error localizedDescription]];
}
// 如果是想做更新操作：只要在更改了实体对象的属性后调用[context save:&error]，就能将更改的数据同步到数据库

// 初始化一个查询请求 
NSFetchRequest *request = [[NSFetchRequest alloc] init];
// 设置要查询的实体 
NSEntityDescription *desc = [NSEntityDescription entityForName:@"Person" inManagedObjectContext:context];
// 设置排序（按照age降序） 
NSSortDescriptor *sort = [NSSortDescriptor sortDescriptorWithKey:@"age" ascending:NO];
request.sortDescriptors = [NSArray arrayWithObject:sort];
// 设置条件过滤(name like '%JN-1%') 
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name like %@", @"*JN-1*"];
request.predicate = predicate;
注意：设置条件过滤时，数据库里面的%要用*来代替
// 执行请求 
NSError *error = nil;
NSArray *objs = [context executeFetchRequest:request error:&error];
if (error) {
   [NSException raise:@"查询错误" format:@"%@", [error localizedDescription]];
}
// 遍历数据 
for (NSManagedObject *obj in objs) {
   NSLog(@"name=%@", [obj valueForKey:@"name"]
}

// 传入需要删除的实体对象
 [context deleteObject:managedObject];
// 将结果同步到数据库NSError *error = nil;
 [context save:&error];
if (error) { 
  [NSException raise:@"删除错误" format:@"%@",[error localizedDescription]];
}

// 那么生成一个Person实体对象就应该这样写 
Person *person = [NSEntityDescription insertNewObjectForEntityForName:@"Person" inManagedObjectContext:context];
person.name = @"JN";person.age = [NSNumber numberWithInt:24];
Card *card = [NSEntityDescription insertNewObjectForEntityForName:@”Card" inManagedObjectContext:context];
card.no = @”447640819";
person.card = card;