Core Data的使用

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/*____________________1.添加数据______________________________*/

for (int i=0; i<10; i++) {

User *user = [NSEntityDescriptioninsertNewObjectForEntityForName:@"User"inManagedObjectContext:self.managedObjectContext];

user.age =@(i+20);

user.name = [NSStringstringWithFormat:@"张%d",i];

user.userId = [NSStringstringWithFormat:@"%d",1000+i];

[selfaddUser:user];

}

/*____________________2.查询______________________________*/

// User *user = [self findUserById:@"1007"];

// NSLog(@"name=%@,age=%@,id=%@",user.name,user.age,user.userId);

///*____________________3.删除______________________________*/

// [self deleteUserById:@"1008"];

//*____________________4.修改______________________________*/

//修改的对象，必须已经在context容器中

// User *user = [self findUserById:@"1007"];

// user.name = @"王五";

// user.age = @10;

// [self.managedObjectContext save:nil];

//一对多的关系，数据操作

// User *user = [self findUserById:@"1007"];

// for (int i=0; i<5; i++) {

// Movie *movie = [NSEntityDescription insertNewObjectForEntityForName:@"Movie" inManagedObjectContext:self.managedObjectContext];

// movie.movieId = [NSString stringWithFormat:@"%d",2000+i];

// movie.name = [NSString stringWithFormat:@"钢铁侠%d",i+1];

// //添加一个用户喜爱的电影

// [user addLoveMovieObject:movie];

// }

// //将修改的数据同步到持久化文件中

// [self.managedObjectContext save:nil];

// User *user = [self findUserById:@"1007"];

// NSSet *lovieMovies = user.loveMovie;

// for (Movie *movie in lovieMovies) {

// NSLog(@"movieName=%@,id=%@",movie.name,movie.movieId);

// }

//添加一个用户

- (BOOL)addUser:(User *)user {

[self.managedObjectContextinsertObject:user];

NSError *error;

BOOL success = [self.managedObjectContextsave:&error];

if (!success) {

NSLog(@"保存失败，error = %@",error);

}

return success;

}

- (User *)findUserById:(NSString *)userId {

//1.创建实体描述对象

NSEntityDescription *entity = [NSEntityDescriptionentityForName:@"User"inManagedObjectContext:self.managedObjectContext];

//2.创建查询对象

NSFetchRequest *request = [[NSFetchRequestalloc] init];

[requestsetEntity:entity];

NSPredicate *predicate = [NSPredicatepredicateWithFormat:@"self.userId=%@"

argumentArray:@[userId]];

//3.设置谓词，定义查询条件

[requestsetPredicate:predicate];

//4.查询

NSArray *users = [self.managedObjectContextexecuteFetchRequest:request error:nil];

return [users lastObject];

}

- (BOOL)deleteUserById:(NSString *)userId {

User *user = [selffindUserById:userId];

//将user对象从context容器中删除

[self.managedObjectContextdeleteObject:user];

//将数据同步写入到持久化文件中

return [self.managedObjectContextsave:nil];

}

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