8
当JSON响应仅包含主键而不是完全嵌套的数组来创建新对象时,我在映射关系时遇到问题。使用主键的RestKit关系映射
我有2个类 - 商店和项目,正如你所期望的商店 - >项目有一对多的关系。
我有一个商店(和项目)的本地核心数据存储,每个都有一个主键。然后,我希望下载一个物品列表作为JSON并映射到核心数据实体,但只包含商店的主键,而不是将所有商店的详细信息都作为嵌套阵列 - 这会对网络流量造成巨大浪费,因为我正在下载500+项目的详细信息。
下面是从两个请求,JSON:
/商店
{
"id" : 1,
"shop" : "Shop A",
"city" : "New York"
},
{
"id" : 2,
"shop" : "Shop B",
"city" : "London"
},
...
/项目
{
"id" : 1,
"name" : "Shoes",
"manufacturer" : "Vans",
"shopId" : 1
},
{
"id" : 2,
"name" : "T-shirt",
"manufacturer" : "Animal",
"shopId" : 2
},
{
"id" : 3,
"name" : "Scarf",
"manufacturer" : "Ted Baker",
"shopId" : 1
},
{
"id" : 4,
"name" : "Sunglasses",
"manufacturer" : "Ray-Ban",
"shopId" : 3
},
...
这里是我的代码的时刻。
AppDelegate.m
...
NSURL *baseURL = [NSURL URLWithString:@"http://localhost/company/API"];
RKObjectManager *objectManager = [RKObjectManager managerWithBaseURL:baseURL];
[AFNetworkActivityIndicatorManager sharedManager].enabled = YES;
[objectManager.HTTPClient setDefaultHeader:@"Accept" value:@"application/json"];
NSManagedObjectModel *managedObjectModel = [NSManagedObjectModel mergedModelFromBundles:nil];
RKManagedObjectStore *managedObjectStore = [[RKManagedObjectStore alloc] initWithManagedObjectModel:managedObjectModel];
objectManager.managedObjectStore = managedObjectStore;
// Shop Mapping
RKEntityMapping *shopMapping = [RKEntityMapping mappingForEntityForName:NSStringFromClass([Shop class])
inManagedObjectStore:objectManager.managedObjectStore];
NSDictionary *shopMappingAttributes = [NSDictionary dictionaryWithObjectsAndKeys:@"objectId",@"id",@"name",@"shop",@"city",@"city",nil];
shopMapping.identificationAttributes = @[@"objectId"];
[shopMapping addAttributeMappingsFromDictionary:shopMappingAttributes];
[objectManager addResponseDescriptor:[RKResponseDescriptor responseDescriptorWithMapping:shopMapping
pathPattern:@"/shops"
keyPath:nil
statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful)]];
// Item Mapping
RKEntityMapping *itemMapping = [RKEntityMapping mappingForEntityForName:NSStringFromClass([Item class])
inManagedObjectStore:objectManager.managedObjectStore];
NSDictionary *itemMappingAttributes = [NSDictionary dictionaryWithObjectsAndKeys:@"objectId",@"id",@"name", @"name",@"manufacturer",@"manufacturer",nil];
itemMapping.identificationAttributes = @[@"objectId"];
[itemMapping addAttributeMappingsFromDictionary:itemMappingAttributes];
// Define the relationship mapping
[objectManager addResponseDescriptor:[RKResponseDescriptor responseDescriptorWithMapping:itemMapping
pathPattern:@"/items"
keyPath:nil
statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful)]];
...
ItemsTableViewController.m
- (void)viewDidLoad {
[super viewDidLoad];
// Update Shops
[[RKObjectManager sharedManager] getObjectsAtPath:@"/shops"
parameters:nil
success:nil
failure:^(RKObjectRequestOperation *operation, NSError *error) {
NSLog(@"Error: %@",error);
}];
// Update/Get Items
NSDictionary *parameters = @{
@"username": self.username,
@"password": self.password,
@"API_key": @"abc123",
};
NSMutableURLRequest *request = [[RKObjectManager sharedManager] requestWithObject:nil
method:RKRequestMethodPOST
path:@"/items"
parameters:parameters];
RKManagedObjectRequestOperation *operation = [[RKObjectManager sharedManager] managedObjectRequestOperationWithRequest:request managedObjectContext:[RKManagedObjectStore defaultStore].mainQueueManagedObjectContext
success:^(RKObjectRequestOperation *operation, RKMappingResult *mappingResult) {
Item *item = [mappingResult firstObject];
NSLog(@"Mapped the Item: %@", item);
} failure:^(RKObjectRequestOperation *operation, NSError *error) {
NSLog(@"Error: %@",error);
}];
NSOperationQueue *operationQueue = [NSOperationQueue new];
[operationQueue addOperation:operation];
}
编辑: 韦恩,我有这在应用程序代理相关的地方,但得到的NSException
NSEntityDescription *itemEntity = [NSEntityDescription entityForName:@"Item" inManagedObjectContext:managedObjectStore.mainQueueManagedObjectContext];
NSRelationshipDescription *shopRelationship = [itemEntity relationshipsByName][@"shop"];
RKConnectionDescription *connection = [[RKConnectionDescription alloc] initWithRelationship:shopRelationship attributes:@{ @"shopId": @"objectId" }];
[itemMapping addConnection:connection];
NSException
*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '+entityForName: nil is not a legal NSManagedObjectContext parameter searching for entity name 'Item''
有什么我错过了?
谢谢@Wain。这段代码是在App Delegate还是View Controller? Andy – Andy
将它添加到'itemMapping'中,您之前曾尝试添加关系映射(但是对于嵌套项目)。 – Wain
我收到一个异常 - 请参阅编辑。这是因为我没有创建项目的瞬态属性?如果是这样如何?安迪 – Andy