Question

我现在面临的一个问题是，当我尝试保存对象时，Core Data似乎只保存第一个。

保存对象的代码

- (void)savingResCore {
AppDelegate *delegate = [[UIApplication sharedApplication]delegate];
NSManagedObjectContext *context = [delegate managedObjectContext];
ResultMO *resEntity = [NSEntityDescription insertNewObjectForEntityForName:@"Result" inManagedObjectContext:context];

if(indCheck == 1) {
  resEntity.result1 = pena1;
  resEntity.resuName1 = penaNam1;
}
if(indCheck == 2) {
  resEntity.result2 = pena2;
  resEntity.resuName2 = penaNam2;
}
if(indCheck == 3) {
  resEntity.result3 = pena3;
  resEntity.resuName3 = penaNam3;
}
_seqNameChk = [NSNumber numberWithInt:[_seqNameChk intValue] - 1];

if([_seqNameChk isEqual:@(0)]){
    NSError *error = nil;
    if (context != nil) {
        if ([context hasChanges] && ![context save:&error]) {
            NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
            abort();
        }
    }
 }
 }

获取对象的代码

- (void)fetchResCore {
AppDelegate *delegate = [[UIApplication sharedApplication]delegate];
NSManagedObjectContext *context = [delegate managedObjectContext];
NSEntityDescription *descriptor = [NSEntityDescription entityForName:@"Result" inManagedObjectContext:context];
NSFetchRequest *request = [[NSFetchRequest alloc]init];
request.entity = descriptor;
NSError *error;
NSArray *contArr = [context executeFetchRequest:request error:&error];
if(contArr == nil){
    NSLog(@"Problems fetching data.");
}
else if(contArr != nil) {
    if(contArr.count == 0) {
        NSLog(@"No objects saved");
    }
    else {
    NSManagedObject *resu = (NSManagedObject *)[contArr objectAtIndex:0];
    NSLog(@"1 - %@", resu);
    pena1 = [resu valueForKey:@"result1"];
    penaNam1 = [resu valueForKey:@"resuName1"];
    NSLog(@"%@", pena1);
    pena2 = [resu valueForKey:@"result2"];
    penaNam2 = [resu valueForKey:@"resuName2"];
    NSLog(@"%@", pena2);
    pena3 = [resu valueForKey:@"result3"];
    penaNam3 = [resu valueForKey:@"resuName3"];
    NSLog(@"%@", pena3);
    NSLog(@"2 - %@", resu);
    }
}
}

例如，我有一个按钮，每按一次按{1}}，每次调出indCheck方法时都会增加fetchResCore。假设seqNameChk = 2。第一次，属性result1＆amp; resuName1成功保存。连续按下该按钮后，它不再保存数据。因此，属性result2，resuName2，result3＆amp;在resuName3方法检索时，fetchResCore不包含数据。

在resu

的控制台中打印结果

resuName1 = "(\n    Alan\n)";
resuName2 = nil;
resuName3 = nil;
result1 = "(\n    100\n)";
result2 = nil;
result3 = nil;

在contArr

的控制台中打印结果

result1 = \"(\\n    100\\n)\";\n    result2 = nil;\n    result3 = nil;\n
resuName1 = \"(\\n    Alan\\n)\";\n    resuName2 = nil;\n    resuName3 = nil;\n

Answer 1

正如Jon Rose指出的那样，

我会假设它们都在数组contArr中，但您只看第一个：NSManagedObject *resu = (NSManagedObject *)[contArr objectAtIndex:0];

我打印出contArr.count，结果是3.我还使用for循环打印出数组的内容，并再次显示已填充的3个元素。

要解决这个问题，我必须纠正[contArr objectAtIndex:0]，因为它只显示数组中的第一个元素。

在fetchResCore方法

中

for(int i = 0; i < contArr.count; i++){
    NSManagedObject *resu = (NSManagedObject *)[contArr objectAtIndex:i];
    NSLog(@"1 - %@", resu);
    if(pena1.count == 0 && penaNam1.count == 0){
    pena1 = [resu valueForKey:@"result1"];
    penaNam1 = [resu valueForKey:@"resuName1"];
    NSLog(@"%@", pena1);
    }
    if(pena2.count == 0 && penaNam2.count == 0){
    pena2 = [resu valueForKey:@"result2"];
    penaNam2 = [resu valueForKey:@"resuName2"];
    NSLog(@"%@", pena2);
    }
    if(pena3.count == 0 && penaNam3.count == 0){
    pena3 = [resu valueForKey:@"result3"];
    penaNam3 = [resu valueForKey:@"resuName3"];
    NSLog(@"%@", pena3);
    }
}

再次感谢Jon Rose指出了一个简单的错误，这个错误花了我几天时间才弄明白。

只能保存第一个对象

1 个答案: