Question

我正在研究RestKit框架及其工作原理。然后我创建一个简单的项目，它将调用Github api并将数据加载到tableview中 - 在我读过的一些教程之后 - 关于从远程加载和映射它工作正常并加载到tableview但是当我试图从中获取时数据存储 - 离线模式 - 应用程序将崩溃，这是日志：

2012-07-29 16:21:41.611 RKGithubClient_FromZtoH[29181:c07] I restkit:RKLog.m:33 RestKit initialized...
2012-07-29 16:21:53.161 RKGithubClient_FromZtoH[29181:c07] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'executeFetchRequest:error: A fetch request must have an entity.'
*** First throw call stack:
(0x20b9022 0x197acd6 0xf15871 0x643c 0x42e5 0x3e14 0x4697 0x53838f 0x5385eb 0x5394ed 0x4a6a0c 0x4abf92 0x4a614b 0x495550 0x495670 0x495836 0x49c72a 0x2a6a 0x46d386 0x46e274 0x47d183 0x47dc38 0x471634 0x25e1ef5 0x208d195 0x1ff1ff2 0x1ff08da 0x1fefd84 0x1fefc9b 0x46dc65 0x46f626 0x259d 0x2505)
terminate called throwing an exception

这是fetchFromDataStore方法：

- (void)fetchFromDataStore
{
    NSFetchRequest *request = [[[RKObjectManager sharedManager] mappingProvider] fetchRequestForResourcePath:self.resourcePath]; //self resourcePath]];
    self.repos = [GithubRepo objectsWithFetchRequest:request];
    [self.tableView reloadData];
}

我知道为什么会发生这种情况，因为我已经为他们创建了实体，你可以从这个链接中查看源代码：

Source Code

此外，是否有任何有用的示例或教程用于RestKit缓存？

谢谢，

Answer 1

最后，我得到了答案..

问题与以下事实有关：当我要求： NSFetchRequest * request = [[[[RKObjectManager sharedManager] mappingProvider] fetchRequestForResourcePath：self.resourcePath]; 在myViewController.m上，它返回空。发生这种情况的原因是因为尚未将对象映射器配置为正确处理核心数据高速缓存。我正在使用：

- (void)setObjectMapping:(RKObjectMappingDefinition *)objectMapping forResourcePathPattern:(NSString *)resourcePathPattern;

虽然我应该使用：

- (void)setObjectMapping:(RKObjectMappingDefinition *)objectMapping forResourcePathPattern:(NSString *)resourcePathPattern withFetchRequestBlock:(RKObjectMappingProviderFetchRequestBlock)fetchRequestBlock;

它位于对象映射的Core数据扩展中。您提供的额外块用于决定需要哪个获取请求，具体取决于resourcePath中传递的参数（在本例中为用户RestKit）。在特定情况下，我想要在repo的用户==“RestKit”时返回一个查找repos的获取请求。

虽然很难找到这种方法的文档，但非常有帮助：

/**
 Configures an object mapping to be used when during a load event where the resourcePath of
 the RKObjectLoader instance matches resourcePathPattern.

 The resourcePathPattern is a SOCKit pattern matching property names preceded by colons within
 a path. For example, if a collection of reviews for a product were loaded from a remote system
 at the resourcePath @"/products/1234/reviews", object mapping could be configured to handle
 this request with a resourcePathPattern of @"/products/:productID/reviews".

 **NOTE** that care must be taken when configuring patterns within the provider. The patterns
 will be evaluated in the order they are added to the provider, so more specific patterns must
 precede more general patterns where either would generate a match.

 @param objectMapping The object mapping to use when the resourcePath matches the specified
 resourcePathPattern.
 @param resourcePathPattern A pattern to be evaluated using an RKPathMatcher against a resourcePath
 to determine if objectMapping is the appropriate mapping.
 @param fetchRequestBlock A block that accepts an individual resourcePath and returns an NSFetchRequest
 that should be used to fetch the local objects associated with resourcePath from CoreData, for use in
 properly processing local deletes
 @see RKPathMatcher
 @see RKURL
 @see RKObjectLoader
 */
- (void)setObjectMapping:(RKObjectMappingDefinition *)objectMapping forResourcePathPattern:(NSString *)resourcePathPattern withFetchRequestBlock:(RKObjectMappingProviderFetchRequestBlock)fetchRequestBlock;

RestKit - fetchFromDataStore（缓存）问题

1 个答案: