Question

我有以下文件：

ProductViewController.h
ProductViewController.m
ComponentsViewController.h
ComponentsViewController.m

在ProductViewController.m内我有我的按钮，我使用核心数据将产品的信息保存到我的 sqlite 数据库。在ComponentsViewController.m内，我有我的按钮，可将组件的信息保存到我的 sqlite 。我在我的datamodel中创建了一对多（产品到组件）关系。我的问题是当我保存我的组件信息而不是将组件分配给我已经创建的产品时，信息被保存到我按下保存组件按钮时创建的“空”产品。在我的代码下面：

ProductViewController.m

- (IBAction)saveProductButton:(id)sender {




    // Add product info to Data base

Product *newProduct = [NSEntityDescription insertNewObjectForEntityForName:@"Product" inManagedObjectContext:self.managedObjectContext];

    newProduct.prdname = self.name.text;
newProduct.prdtdesc = self.prdtdesc.text;
newProduct.prdtid = self.prdtid.text;

    NSError *error;
    if (![self.managedObjectContext save:&error]) {
        NSLog(@"Whoops, couldn't save: %@", [error localizedDescription]);
    }
    //  4
    self.name.text = @"";
    self.prdtid.text = @"";
    self.prdtdesc.text = @"";

    //  5
    [self.view endEditing:YES];
}


ComponentsViewController.m

- (IBAction)addComponent:(id)sender {



Product *newProduct = [NSEntityDescription insertNewObjectForEntityForName:@"Product" inManagedObjectContext:self.managedObjectContext];

 Components * newComponent = [NSEntityDescription insertNewObjectForEntityForName:@"Components"
 inManagedObjectContext:self.managedObjectContext];
 newComponent.prdtcompname = self.prdtcompname.text;
newComponent.prdtcompid = self.prdtcompid.text;
newComponent.prdtcompdesc = self.prdtcompdesc.text;
newComponent.prdtcompqt = self.prdtcompQT.text;

newProduct.tocomponents = [NSSet setWithObjects:newComponent, nil];


 NSError *error;
 if (![self.managedObjectContext save:&error]) {
 NSLog(@"Whoops, couldn't save: %@", [error localizedDescription]);
 }
 //  4

 self.prdtcompQT.text = @"";
 self.prdtcompname.text = @"";
 self.prdtcompid.text = @"";
 self.prdtcompdesc.text = @"";
 //  5
 [self.view endEditing:YES];

}

Answer 1

在创建组件时不要创建新产品。在创建组件时，只需获取具有相对ID的产品并将产品引用存储在组件中。

以下是我的示例代码：

我创建了一种相同的一对多关系（Item - ＆gt; Item_Details）

步骤1：首先我在项目实体中插入。

第2步：插入item_Details时，我只使用相对ID从Item实体获取item.info。

创建NSManagedObjectSubClass（带关系）后，它会自动创建你提到的引用实例。

#import <Foundation/Foundation.h>
#import <CoreData/CoreData.h>

@class Item;

@interface Item_Detail : NSManagedObject


@property (nonatomic, retain) NSNumber * item_Id;      // Item_Id is a common id in both item and Item_details should act as a relation.
@property (nonatomic, retain) NSString * item_Size;
@property (nonatomic, retain) NSString * last_Modified;
@property (nonatomic, retain) NSNumber * price;

@property (nonatomic, retain) Item *itemInfo;  // RelationShip reference

@end

//使用关系ID获取项目信息：

 +(Item *)getSourceItemDetail:(NSNumber *)itemId
    {
        NSEntityDescription *itemEntity = [NSEntityDescription entityForName:@"Item" inManagedObjectContext:[ASDataManager managedObjectContext]];
        NSFetchRequest *itemFetchRqt= [[NSFetchRequest alloc]init];
        [itemFetchRqt setEntity:itemEntity];

        NSPredicate *itempredicate = [NSPredicate predicateWithFormat:@"item_Id = %@",itemId];
        [itemFetchRqt setPredicate:itempredicate];
        NSError *error = nil;
        NSArray *resultArray = [[ASDataManager managedObjectContext] executeFetchRequest:itemFetchRqt error:&error];

        if([resultArray count] == 1)
        {
            Item *item = (Item *)[resultArray objectAtIndex:0];
            return item;
        }
        return nil;
    }


//Item_Detail _Insertion
+(void)insertNewItemDetailRecordInItemDetailTable:(NSDictionary *)itemDetailDic
{

    Item_Detail *item_Dtls = (Item_Detail *)[NSEntityDescription insertNewObjectForEntityForName:@"Item_Detail" inManagedObjectContext:[ASDataManager managedObjectContext]];


    item_Dtls.item_Id = [NSNumber numberWithInt:[[itemDetailDic valueForKey:@"Item_ID"] intValue]];
    item_Dtls.item_Size = [ASGlobalInfoHelper getValueIfNotNullFrom:[itemDetailDic objectForKey:@"Item_Size"] valueType:ValueTypeString];

    item_Dtls.itemInfo = [self getSourceItemDetail:[NSNumber numberWithInt:@"90"]];
    //Getting Relationship data
    if(![[ASDataManager managedObjectContext] save:nil])
        NSLog(@"Error in Save");


}

Answer 2

在ComponentsViewController.m中，您要在此处创建一个空产品：

Product *newProduct = [NSEntityDescription insertNewObjectForEntityForName:@"Product" inManagedObjectContext:self.managedObjectContext];

如果您希望与新创建的Components对象与先前创建的Product对象建立关系，则必须使用FetchRequest从核心数据中获取产品或传递Product从ProductViewController到ComponentsViewController。

核心数据关系

2 个答案: