核心数据 - 使用谓词过滤多对多关系

Question

我的核心数据模型中有以下两个实体：

Manufacture {name, ...other attributes}
Product {name, .... other attributes}

我设置了一对多的关系：

Manufacturer.manufactures <------>> Product.manufacturedBy

我正在尝试构建一个谓词，以返回属于制造商的所有匹配搜索字符串的产品。例如。如果有两个制造商，“King Nut”和“Queen Nut”，那么搜索“Nut”应该归还King Nut和Queen Nut制作的所有产品。

当我的过滤器在Product实体上时，我的谓词工作正常，但是当在Manufacturer实体上过滤时，我无法获得任何谓词。结果集为空。

NSEntityDescription *entity = [NSEntityDescription entityForName:@"Product" inManagedObjectContext:[GBKDB context]];
searchValue = @"nut";
NSString *wildcardString = [NSString stringWithFormat:@"*%@*", searchValue];

我尝试了以下内容：

    predicate = [NSPredicate predicateWithFormat:@"manufacturedBy.name CONTAINS[cd] %@",searchValue];
    predicate = [NSPredicate predicateWithFormat:@"manufacturedBy.name like %@",wildcardString];
    predicate = [NSPredicate predicateWithFormat:@"manufacturedBy.name matches %@",wildcardString];
    predicate = [NSPredicate predicateWithFormat:@"ALL manufacturedBy.name like %@",wildcardString];
    predicate = [NSPredicate predicateWithFormat:@"ALL manufacturedBy.name like[cd] %@",@wildcardString];

Answer 1

要获得名称中包含“nut”的制造商生产的Product，您的请求应如下所示：

NSString* searchVal = @"nut";
NSFetchRequest* r = [[NSFetchRequest alloc] initWithEntityName:@"Product"];
[r setPredicate:[NSPredicate predicateWithFormat:@"manufacturedBy.name CONTAINS[cd] %@",searchVal]];

要获取包含“坚果”的产品名称的Manufacturer，您的请求应如下所示：

NSString* searchVal = @"nut";
NSFetchRequest* r = [[NSFetchRequest alloc] initWithEntityName:@"Manufacture"];
[r setPredicate:[NSPredicate predicateWithFormat:@"ANY manufactures.name CONTAINS[cd] %@",searchVal]];

如果结果集为空，可能是因为没有对象回答谓词（包含子串“nut”）。
尝试添加一些具有已知名称和测试的假实体。

修改 这是您可以用于测试的代码：

typedef void(^config_block_t)(id);

- (void) synthesizeObjectsOfEntity:(NSString*)entity
                           context:(NSManagedObjectContext*)context
                             count:(NSUInteger)count
                       configBlock:(config_block_t)configBlock
{
    for (;count;--count) {
        NSManagedObject* object = [NSEntityDescription insertNewObjectForEntityForName:entity
                                                                inManagedObjectContext:context];
        configBlock(object);
    }
}

- (void) synthesizeProductsAndManufacturersInContext:(NSManagedObjectContext*)context
{
    NSMutableArray* manufacturers = [NSMutableArray new];
    [self synthesizeObjectsOfEntity:@"Manufactur"
                            context:context
                              count:10
                        configBlock:^(Manufactur* m) {
                            m.name = [NSString stringWithFormat:@"m-%u%u%u",arc4random()%10,arc4random()%10,arc4random()%10];
                            [manufacturers addObject:m];
                        }];
    [self synthesizeObjectsOfEntity:@"Product"
                            context:context
                              count:100
                        configBlock:^(Product* p) {
                            p.name = [NSString stringWithFormat:@"p-%u%u%u",arc4random()%10,arc4random()%10,arc4random()%10];
                            p.manufacturedBy = manufacturers[arc4random() % [manufacturers count]];
                        }];
    [context save:NULL];
    [context reset];
    NSString* searchVal = @"3";
    NSFetchRequest* r = [[NSFetchRequest alloc] initWithEntityName:@"Product"];
    [r setPredicate:[NSPredicate predicateWithFormat:@"manufacturedBy.name CONTAINS[cd] %@",searchVal]];
    NSArray* match = [context executeFetchRequest:r error:NULL];
    NSLog(@"matched: %u",[match count]);
}

Answer 2

查看Apple的this文档。它做了一个例子来做你试图用“任何”谓词做的事情。