如何删除核心数据中的条目

Posted 2023-03-04

【中文标题】如何删除核心数据中的条目

【英文标题】：How to delete entries in core data

【发布时间】：2017-04-20 13:19:08

【问题描述】：

我是核心数据的新手..

我知道如何存储和物品。

- (void)dbSave:(NSString *)uri withContent:(NSDictionary *)content withExpiry:(double)date 
Cache *cache = [self dbLoad:uri];
if (cache == nil) 
    cache = [NSEntityDescription insertNewObjectForEntityForName:@"Cache" inManagedObjectContext:[self managedObjectContext]];


double time = (double) [[NSDate date] timeIntervalSince1970] + date;

[cache setLocal:uri];
[cache setTime:@(time)];

NSMutableData *data = [[NSMutableData alloc] init];

NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];
[archiver encodeObject:content forKey:@"data"];
[archiver finishEncoding];

[cache setData:data];

NSError *error;
if (![[self managedObjectContext] save:&error]) 

但我坚持创建一种方法来清除这个核心数据库。有人知道怎么做吗？

【问题讨论】：

您是否要求删除所有表格？丢一张桌子？还是从表中删除一个字段？

查看此链接***.com/questions/1077810/…

Removing a specific entry/row from Core-Data的可能重复

@Brandon 实体下名为缓存的所有内容

【参考方案1】：

NSManagedObjectContext *managedObjectContext=[appDelegate managedObjectContext];
NSFetchRequest *fetchRequest=[NSFetchRequest fetchRequestWithEntityName:@"entity"];
NSArray* currentRecord = [[managedObjectContext executeFetchRequest:fetchRequest error:nil] mutableCopy];

if (currentRecord.count)

    for (NSManagedObject *obj in currentRecord)
    
        [managedObjectContext deleteObject:obj];
    
    NSError * error = nil;

    if (![managedObjectContext save:&error])
        NSLog(@"Can't save ! %@ %@",error,[error localizedDescription]);
    else
        NSLog(@"Data deleted");

【参考方案2】：

使用这个

NSManagedObjectContext *managedContext = [[APP_DELEGATE dbManagerObj] newPrivateContext];

NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"Cache"];
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"isUserData = %@",[NSNumber numberWithBool:true]];
[fetchRequest setPredicate:predicate];
if (IS_ios9_ANDABOVE) 
    NSBatchDeleteRequest *batchDeleteRequest = [[NSBatchDeleteRequest alloc]initWithFetchRequest:fetchRequest];
    [[[APP_DELEGATE dbManagerObj]persistentStoreCoordinator]executeRequest:batchDeleteRequest withContext:managedContext error:nil];

else

   NSArray *userRelatedDay = [managedContext executeFetchRequest:fetchRequest error:nil];
    for (NSManagedObject *object in userRelatedDay) 
        [managedContext deleteObject:object];