CoreData|CoreData 增删改查 CoreData增删改查

CoreData增删改查 1.1-CoreData增加数据

Person *p = [NSEntityDescriptioninsertNewObjectForEntityForName:@"Person"inManagedObjectContext:kManagedObjectContext.managedObjectContext]; p.age= @(13); p.name=@"张三"; [kManagedObjectContext save];

1.2-CoreData查询数据

//1.创建一个查询请求 NSFetchRequest *request = [[NSFetchRequest alloc] initWithEntityName:@"Person"]; //2.创建查询谓词（查询条件） NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name == %@",@"张三"]; //3.给查询请求设置谓词 request.predicate = predicate; //4.查询数据 NSArray *arr = [kManagedObjectContext.managedObjectContext executeFetchRequest:request error:nil]; NSLog(@"%@====%@",arr.firstObject.name,arr.firstObject.age);

1.3-CoreData修改数据

//1.创建一个查询请求 NSFetchRequest *request = [[NSFetchRequest alloc] initWithEntityName:@"Person"]; //2.创建查询谓词（查询条件） NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name == %@",@"张三"]; //3.给查询请求设置谓词 request.predicate = predicate; //4.查询数据 NSArray *arr = [kManagedObjectContext.managedObjectContext executeFetchRequest:request error:nil]; //5.改变数据 arr.firstObject.name = @"李四"; arr.firstObject.age = @(18); //6.同步到数据库 [kManagedObjectContext save];

1.4-CoreData删除数据

//1.创建一个查询请求 NSFetchRequest *request = [[NSFetchRequest alloc] initWithEntityName:@"Person"]; //2.创建查询谓词（查询条件） NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name == %@",@"张三"]; //3.给查询请求设置谓词 request.predicate = predicate; //4.查询数据 NSArray【CoreData|CoreData 增删改查】 *arr = [kManagedObjectContext.managedObjectContext executeFetchRequest:request error:nil]; //5.删除数据 [kManagedObjectContext.managedObjectContext deleteObject:arr.firstObject]; //6.同步到数据库 [kManagedObjectContext save];

1.5-CoreData清空数据库

清空数据库可以使用删除文件的方式
通过沙盒路径进入到沙盒可以看到数据库文件有三个，我们逐一删除便可
代码中的kFileName是一个宏表示创建的路径

NSFileManager *fileManager = [NSFileManager defaultManager]; NSString *documentsPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0]; //沙盒中三个文件 NSString *filePath1 = [documentsPath stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.db",kFileName]]; NSString *filePath2 = [documentsPath stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.db-shm",kFileName]]; NSString *filePath3 = [documentsPath stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.db-wal",kFileName]]; NSError *error; BOOL success = [fileManager removeItemAtPath:filePath1 error:&error]; [fileManager removeItemAtPath:filePath2 error:nil]; [fileManager removeItemAtPath:filePath3 error:nil]; if (success) { NSLog(@"Remove fiel:%@ Success!",kFileName); } else { NSLog(@"Could not delete file -:%@ ",[error localizedDescription]); }