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PORestKit Mapping objects within a default relationship using a specified primary key reference
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copied!<p>I am currently developing an iOS Messenger application and I would like to talk about these two classes relationship: <code>MessengerConversation</code> and <code>MessengerMessage</code>.</p> <p>Supposing that I already have a local MessengerConversation instance which can have many MessengerMessage instances related into its <code>messages</code> relationship property, I would like to request and mapping the following JSON payload:</p> <p>Request: GET /conversations/:conversationID/msgs <br> Response:</p> <pre><code>{ "messages": [ { ... "messageid": n, "content": "..." ... }, ... ] } </code></pre> <p>As the response JSON payload didn't indicate which conversation the delivered messages are from. I used the following approach to fix this issue into my <code>MessengerManager</code> class (Responsible for interacting with the shared RKObjectManager instance):</p> <pre><code>- (void)objectLoader:(RKObjectLoader *)objectLoader willMapData:(inout id *)mappableData { // // GETs Resource Paths. if ([objectLoader method] == RKRequestMethodGET) { if ([pathMatcherConversationsMessagesGET matchesPath:objectLoader.resourcePath tokenizeQueryStrings:NO parsedArguments:Nil]) { // // Get requested conversationID from the following resource path Pattern: // kMessengerManagerResourcePathMessages: /conversations/:conversationID/msgs NSNumber *currentConversationID = Nil; NSDictionary *arguments = Nil; BOOL isMatchingPattern = [pathMatcherConversationsMessagesGET matchesPattern:kMessengerManagerResourcePathConversationsMessagesGET tokenizeQueryStrings:YES parsedArguments:&arguments]; if (isMatchingPattern) { currentConversationID = [arguments objectForKey:@"conversationID"]; // // Get the original returned array of messages: NSArray *origMessagesArray = [*mappableData valueForKeyPath:@"messages"]; NSMutableArray *reformattedData = [NSMutableArray arrayWithCapacity:[origMessagesArray count]]; // // Create copies of objects adding the already knew reference. for (NSDictionary *origMessagesArrayObject in origMessagesArray) { NSMutableDictionary *newMessagesArrayObject = [origMessagesArrayObject mutableCopy]; [newMessagesArrayObject setObject:currentConversationID forKey:@"conversationid"]; [reformattedData addObject:newMessagesArrayObject]; } // // Replace the new objects instead of the response objects [*mappableData setObject:reformattedData forKey:@"messages"]; } } } } </code></pre> <p>And so everything worked properly. That is, all loaded MessengerMessages from the specified MessengerConversation (into the RKObjectLoader resource path) are being inserted into the wanted relationship. </p> <p>Now comes the real problem, as I am working with my MessengerManager class which adopts the RKObjectLoaderProtocol, I could implement the <code>objectLoader:willMapData:</code> method. But as my View classes are using the <code>RKFetchedResultsTableController</code> and every table controller instance is also its RKObjectLoader delegate, I don't know which would be the best practice to enable a RKFetchedResultsTableController instance to update a received JSON payload before the mapping operation.</p> <p>Shall I subclass it?</p> <p>And are there better ways to map received objects into a pre-defined object specified by a RKObjectLoader resource path (e.g: GET /conversations/2/msg where all resulted messages should be mapped inside the defined MessengerConversation object with its primary key value equal to 2)?</p> <p>Best regards,<br> Piva</p>

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