Unable to build Xamarin iOS Project

Question

Due to a requirement to use a 3rd party security wrapper for our app we have to downgrade to XCode6.4 and now we're having issues trying to build the project due to an error with one of the .xib files. I've removed all references to this .xib and the project builds so it must be something to do with an XCode7/iOS9 only feature being used in the XIB. Any ideas?

    /Users/devarchitecture/Fundamentals/Fundamentals.iOS/Views/TableViewCells/ReportCell.xib: Error: 2016-04-13 13:29:58.717 ibtoold[10374:761527] [MT] DVTAssertions: ASSERTION FAILURE in /SourceCache/IDEInterfaceBuilder/IDEInterfaceBuilder-7706/InterfaceBuilderKit/Document/Archiving/IBDocumentUnarchiver.m:221
Details:  Failed to unarchive an instance of IBUIScreenMetrics
Object:   <IBDocumentUnarchiver: 0x7f82b84f5d40>
Method:   -unarchiveObjectFromElement:
Thread:   <NSThread: 0x7f82b8441910>{number = 1, name = main}
Hints: None
Backtrace:
  0  0x0000000100886c07 -[DVTAssertionHandler handleFailureInMethod:object:fileName:lineNumber:assertionSignature:messageFormat:arguments:] (in DVTFoundation)
  1  0x000000010088665f _DVTAssertionHandler (in DVTFoundation)
  2  0x000000010088694e _DVTAssertionFailureHandler (in DVTFoundation)
  3  0x000000010177c85a __51-[IBDocumentUnarchiver unarchiveObjectFromElement:]_block_invoke (in IDEInterfaceBuilderKit)
  4  0x000000010177a93a -[IBDocumentUnarchiver recurseWithElement:kind:invokingBlock:] (in IDEInterfaceBuilderKit)
  5  0x000000010177c3fb -[IBDocumentUnarchiver unarchiveObjectFromElement:] (in IDEInterfaceBuilderKit)
  6  0x000000010177f18f -[IBDocumentUnarchiver unarchiveObjectForKey:defaultValue:] (in IDEInterfaceBuilderKit)
  7  0x0000000107a2e58a (in IDEInterfaceBuilderCocoaTouchIntegration)
  8  0x0000000107a2e020 IBUIUnarchiveSimulatedMetric (in IDEInterfaceBuilderCocoaTouchIntegration)
  9  0x0000000107a2ddf4 (in IDEInterfaceBuilderCocoaTouchIntegration)
10  0x0000000107a2c239 (in IDEInterfaceBuilderCocoaTouchIntegration)
11  0x000000010177c737 __51-[IBDocumentUnarchiver unarchiveObjectFromElement:]_block_invoke (in IDEInterfaceBuilderKit)
12  0x000000010177a93a -[IBDocumentUnarchiver recurseWithElement:kind:invokingBlock:] (in IDEInterfaceBuilderKit)
13  0x000000010177c3fb -[IBDocumentUnarchiver unarchiveObjectFromElement:] (in IDEInterfaceBuilderKit)
14  0x000000010177f18f -[IBDocumentUnarchiver unarchiveObjectForKey:defaultValue:] (in IDEInterfaceBuilderKit)
15  0x0000000101703191 -[IBDocument unarchivePlatformIndependentDataWithUnarchiver:] (in IDEInterfaceBuilderKit)
16  0x0000000101702a6e -[IBDocument unarchiveDocument:] (in IDEInterfaceBuilderKit)
17  0x000000010177a93a -[IBDocumentUnarchiver recurseWithElement:kind:invokingBlock:] (in IDEInterfaceBuilderKit)
18  0x000000010177aba7 -[IBDocumentUnarchiver unarchiveDocument:] (in IDEInterfaceBuilderKit)
19  0x00000001016fa184 __61-[IBDocument decodeContentsOfURL:ofType:decodingStyle:error:]_block_invoke (in IDEInterfaceBuilderKit)
20  0x00000001017472a9 -[IBDocumentAutolayoutManager runBlockInNewArbitrationStackEntryWithBehavior:block:] (in IDEInterfaceBuilderKit)
21  0x000000010172ddd7 -[IBDocument modifyViewsInAutolayoutSafeWayWithoutUpdatingConstraintsDuring:] (in IDEInterfaceBuilderKit)
22  0x00000001016f9f66 -[IBDocument decodeContentsOfURL:ofType:decodingStyle:error:] (in IDEInterfaceBuilderKit)
23  0x00000001016f42b5 __39-[IBDocument readFromURL:ofType:error:]_block_invoke_2 (in IDEInterfaceBuilderKit)
24  0x0000000101752560 -[IBDocumentAutolayoutManager doNotSynchronouslyComputeAutolayoutStatusWhilePerformingBlock:] (in IDEInterfaceBuilderKit)
25  0x00000001016f4111 __39-[IBDocument readFromURL:ofType:error:]_block_invoke (in IDEInterfaceBuilderKit)
26  0x00000001017297db -[IBDocument invokeWithUndoSuppressed:] (in IDEInterfaceBuilderKit)
27  0x00000001016f3dc2 -[IBDocument readFromURL:ofType:error:] (in IDEInterfaceBuilderKit)
28  0x000000010068c590 (in ibtoold)
29  0x00000001006870b4 (in ibtoold)
30  0x000000010068e370 (in ibtoold)
31  0x0000000100694233 (in ibtoold)
32  0x00000001006947b0 (in ibtoold)
33  0x0000000100694683 (in ibtoold)
34  0x000000010068366a (in ibtoold)
35  0x0000000100693e2c (in ibtoold)
36  0x0000000100693074 (in ibtoold)
37  0x00007fff8fcc05c9 start (in libdyld.dylib) 

Answer 1

I had this problem only last week! After comparing .xib files I noticed that the offending .xib contained a simulatedMetricsContainer entry. I removed it, saved and I was able to build the project.

This is what I removed:

   <simulatedMetricsContainer key="defaultSimulatedMetrics">
        <simulatedStatusBarMetrics key="statusBar"/>
        <simulatedOrientationMetrics key="orientation"/>
        <simulatedScreenMetrics key="destination" type="iPad-1/2"/>
    </simulatedMetricsContainer>

I hope this helps.

Steve