显示关系1：M的核心数据实体记录 [英] Display Core Data entity records with relationship 1:M

问题描述

我在显示来自我的实体Product和OrderItems的记录时遇到大问题。这是一对多关系。

I am having big issues displaying records from my entity Product and OrderItems. This is one to Many relationships.

我向Product实体添加了记录而没有任何问题，我在以下函数中执行OrderItem条目：

I added records to Product entity without any problem and I perform OrderItem entry in the following function:

     
     - (IBAction)cmdSave:(id)sender {

          self.product.productName = self.txtProductName.text;

          NSManagedObjectContext *context =[self managedObjectContext];
          OrderItems *oi=
          [NSEntityDescription  
          insertNewObjectForEntityForName:@"OrderItems"  inManagedObjectContext:context];

          [oi setValue:[NSNumber numberWithInteger:[self.txtQty.text integerValue]] forKey:@"ordQty"];
          [oi setValue:[NSNumber numberWithInteger:[self.txtPrice.text integerValue]] forKey:@"price"];
          [oi setValue:[NSNumber numberWithInteger:[self.txtTotal.text integerValue]] forKey:@"total"];
          [oi setOrders:self.product];

           NSError *error = nil;
           if (![context save:&error]) {
           NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
           abort();
          }
           [self.navigationController popViewControllerAnimated:YES];
     }

这似乎没问题，我最大的问题是显示每个产品的所有订单商品。产品====> OrderItems的关系是：产品和逆是订单。 OrderItems ===>产品是：订单和逆是产品。

This seems ok and my biggest issue is display all order items for each Product. The relationship Product ====> OrderItems is:product and the inverse is orders. OrderItems ===>Product is: orders and inverse is product.

我尝试显示fetchedResult

I try to display for fetchedResult

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"Cell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];

    // Configure the cell...
      Product *prod = [self.fetchedResultsController objectAtIndexPath:indexPath];

  *********************
     //I wanted to connect to relationship object and get all orders but I get Incompatible   pointer types initializing 'OrderItems *_Strong ' with an expression of type NSSet.

   ******any ideas? 
    OrderItems *order=prod.product;
    **************************************

    cell.textLabel.text =prod.productName;
    cell.detailTextLabel.text =[NSString stringWithFormat:@"%@",order.price];



    return cell;
}

我知道Product中产品中的关系对象是NSSet如下所示：

I know the relationship object in product in Product is NSSet as below:

     @interface Product : NSManagedObject

     @property (nonatomic, retain) NSString * productName;
     @property (nonatomic, retain) NSNumber * qty;
     @property (nonatomic, retain) NSSet *product;
     @end

     @interface Product (CoreDataGeneratedAccessors)

     - (void)addProductObject:(NSManagedObject *)value;
     - (void)removeProductObject:(NSManagedObject *)value;
     - (void)addProduct:(NSSet *)values;
     - (void)removeProduct:(NSSet *)values;

     @end

我在不同的程序中也采用了相同的方式，但我不知道为什么。

I have done the same way in different program but I don't know really why.

非常感谢任何帮助或建议！

Any help or advice would be much appreciated!

推荐答案

不兼容的指针类型使用NSSet类型的表达式初始化'OrderItems * _Strong'。

Incompatible pointer types initializing 'OrderItems *_Strong ' with an expression of type NSSet.

这非常简单。你几乎似乎知道。问题是：

It's pretty straightforward. You almost seem to know. The problem is:

Product *prod = [self.fetchedResultsController objectAtIndexPath:indexPath];
OrderItems *order=prod.product;

您正在为类型 OrderItems ，你指定的东西是 prod.product 。但那是什么？它是 NSSet ：

You're assigning a value to a pointer of type OrderItems, and the thing you're assigning is prod.product. But what's that? It's an NSSet:

 @property (nonatomic, retain) NSSet *product;

这就是你得到那条消息的原因。你有一个指向 NSSet 的指针，你试图将它指向一个指向 OrderItems 的指针。我不知道 OrderItems 是什么，但它不是 NSSet 。你可以做出这个任务，但是你不能指望它正常工作。

That's why you get that message. You have a pointer to NSSet and you're trying to assign it to a pointer to OrderItems. I don't know what OrderItems is, but it's not an NSSet. You can make that assignment, but you can't expect it to work properly.

我在不同的程序中做了同样的事情，但我不知道为什么。

I have done the same way in different program but I don't know really why.

要么你在其他应用程序中做了不同的事情，要么你在那里得到的信息是相同的来到这里。

Either you did things differently in other apps, or you got the same message there that you're getting here.

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