IOS - CoreData 增删改查

#pragma mark - Core Data Methods

- (void)insertObjectWithFileName:(NSString *)fileName

{

/**

SQL新增记录的过程

1. 拼接一个INSERT的SQL语句

2. 执行SQL

*/

// 1. 实例化并让context“准备”将一条个人记录增加到数据库

ReaderDocument *document = [NSEntityDescription insertNewObjectForEntityForName:kOAPDFDocument inManagedObjectContext:self.managedObjectContext];

// 2. 设置个人信息

document.fileName = fileName;

// 3. 保存(让context保存当前的修改)

if ([self.managedObjectContext save:nil]) {

NSLog(@"新增成功");

} else {

NSLog(@"新增失败");

}

}

- (NSMutableArray *)getObjectsWithPredicate:(NSString *)predicate

{

// 1. 实例化一个查询(Fetch)请求

NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:kOAPDFDocument];

// 3. 条件查询，通过谓词来实现的

//    request.predicate = [NSPredicate predicateWithFormat:@"age < 60 && name LIKE '*五'"];

// 在谓词中CONTAINS类似于数据库的 LIKE '%王%'

//    request.predicate = [NSPredicate predicateWithFormat:@"phoneNo CONTAINS '1'"];

// 如果要通过key path查询字段，需要使用%K

//    request.predicate = [NSPredicate predicateWithFormat:@"%K CONTAINS '1'", @"phoneNo"];

// 直接查询字表中的条件

// 2. 让_context执行查询数据

NSArray *array = [self.managedObjectContext executeFetchRequest:request error:nil];

//    for (OAPDFDocument *pdf in array) {

//        NSLog(@"\nfielName:%@ \nfilePath:%@ \nfileSize:%@", pdf.fileName, pdf.filePath, pdf.fileSize);

// 在CoreData中，查询是懒加载的

// 在CoreData本身的SQL查询中，是不使用JOIN的，不需要外键

// 这种方式的优点是：内存占用相对较小，但是磁盘读写的频率会较高

//        for (Book *b in p.books) {

//            NSLog(@"%@ %@ %@", b.name, b.price, b.author);

//        }

//    }

//    for (Book *b in array) {

//        NSLog(@"%@ %@ %@", b.name, b.price, b.author);

//    }

return [NSMutableArray arrayWithArray:array];

}

- (void)editObjectsWithPredicate:(NSPredicate *)predicate withState:(NSNumber *)state

{

// 1. 实例化一个查询(Fetch)请求

NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:kOAPDFDocument];

// 2. 条件查询，通过谓词来实现的

request.predicate = predicate;

// 在谓词中CONTAINS类似于数据库的 LIKE '%王%'

//    request.predicate = [NSPredicate predicateWithFormat:@"phoneNo CONTAINS '1'"];

// 如果要通过key path查询字段，需要使用%K

//    request.predicate = [NSPredicate predicateWithFormat:@"%K CONTAINS '1'", @"phoneNo"];

// 直接查询字表中的条件

// 3. 让_context执行查询数据

NSArray *array = [self.managedObjectContext executeFetchRequest:request error:nil];

for (ReaderDocument *pdf in array) {

// 3.1修改公文阅读状态

pdf.fileTag = state;

// 3.2修改公文最新打开日期

NSFileManager* fileMngr = [NSFileManager defaultManager];

NSDictionary* attributes = [fileMngr attributesOfItemAtPath:pdf.fileURL error:nil];

pdf.lastOpen = (NSDate *)[attributes objectForKey:NSFileModificationDate];

// 3.3获取并保存，该文件的首页缩略图

UIImage *thumbImage = [pdf imageFromPDFWithDocumentRef:pdf.fileURL];

pdf.thumbImage = UIImagePNGRepresentation(thumbImage);

[self.collectionView reloadData];

break;

}

// 4. 通知_context修改数据是否成功

if ([self.managedObjectContext save:nil]) {

NSLog(@"修改成功");

} else {

NSLog(@"修改失败");

}

}

- (void)removeObjectsWithPredicate:(NSString *)predicate

{

// 1. 实例化查询请求

NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:kOAPDFDocument];

// 2. 设置谓词条件

//    request.predicate = [NSPredicate predicateWithFormat:@"name = '张老头'"];

request.predicate = [NSPredicate predicateWithFormat:predicate];

// 3. 由上下文查询数据

NSArray *result = [self.managedObjectContext executeFetchRequest:request error:nil];

// 4. 输出结果

for (ReaderDocument *pdf in result) {

// 删除一条记录

[self.managedObjectContext deleteObject:pdf];

BOOL fileExists = [[NSFileManager defaultManager] fileExistsAtPath:pdf.filePath];

if (fileExists) {

[self removeFileWithName:pdf.fileName];

}else{

NSLog(@"File:%@ is not exist!",pdf.fileName);

}

//        break;

}

// 5. 通知_context保存数据

if ([self.managedObjectContext save:nil]) {

NSLog(@"删除%lu文件成功",(unsigned long)[result count]);

} else {

NSLog(@"删除失败");

}

}

- (void)removeFileWithName:(NSString *)fileName

{

NSFileManager *fileManager = [NSFileManager defaultManager];

NSString *documentsPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];

NSString *filePath = [documentsPath stringByAppendingPathComponent:fileName];

NSError *error;

BOOL success = [fileManager removeItemAtPath:filePath error:&error];

if (success) {

NSLog(@"Remove fiel:%@ Success!",fileName);

}

else

{

NSLog(@"Could not delete file -:%@ ",[error localizedDescription]);

}

}