title: How do I make an array of RLMObjects be a property of a Realm class?
body: <p>I am trying to relate words to sentence objects and have sentences be made up of word objects.</p>
  
  <p>This is what I want to do:</p>
  
  <pre><code>class Word: RLMObject {
      dynamic var sentences = [Sentence]
      dynamic var spanish = ""
      dynamic var english = ""
  }
  
  class Sentence: RLMObject {
      dynamic var content = [Word]
      dynamic var machineTranslation = ""
  }
  
  word1 = Word.objectsWhere("spanish == 'hola'").firstObject()
  word2 = Word.objectsWhere("spanish == 'amigo'").firstObject()
  
  let sentence1 = [word1,word2]
  
  var Realm = RLMRealm.defaultRealm()
  Realm.beginWriteTransaction()
  Realm.addObject(sentence1)
  Realm.commitWriteTransaction()
  </code></pre>
  
  <p>I am getting this in my debug console:</p>
  
  <pre><code>2014-12-03 12:42:36.139 MyApp [5743:586150] *** Terminating app due to uncaught exception 'RLMException', reason: ''(null)' is not supported as an RLMObject property. All properties must be primitives, NSString, NSDate, NSData, RLMArray, or subclasses of RLMObject. See http://realm.io/docs/cocoa/api/Classes/RLMObject.html for more information.'
  *** First throw call stack:
  (
      0   CoreFoundation                      0x0000000105c72f35 __exceptionPreprocess + 165
      1   libobjc.A.dylib                     0x00000001077f2bb7 objc_exception_throw + 45
      2   MyApp                               0x000000010578bd0f -[RLMProperty setTypeFromRawType] + 1155
      3   MyApp                               0x000000010578c108 -[RLMProperty initSwiftPropertyWithName:attributes:property:instance:] + 391
      4   MyApp                               0x0000000105785a6d +[RLMObjectSchema propertiesForClass:] + 412
      5   MyApp                               0x0000000105785341 +[RLMObjectSchema schemaForObjectClass:createAccessors:] + 318
      6   MyApp                               0x00000001057abdfc __23+[RLMSchema initialize]_block_invoke + 769
      7   libdispatch.dylib                   0x0000000107f977f4 _dispatch_client_callout + 8
      8   libdispatch.dylib                   0x0000000107f84343 dispatch_once_f + 565
      9   libobjc.A.dylib                     0x00000001077f34d6 _class_initialize + 648
      10  libobjc.A.dylib                     0x00000001077fc6e1 lookUpImpOrForward + 351
      11  libobjc.A.dylib                     0x00000001078090d3 objc_msgSend + 211
      12  MyApp                               0x0000000105782826 -[RLMObject init] + 38
      13  MyApp                               0x000000010577011b _TFC11MyApp      4WordcfMS0_FT_GSQS0__ + 315
      14  MyApp                               0x0000000105770292 _TFC11MyApp      4WordCfMS0_FT_GSQS0__ + 50
      15  MyApp                               0x000000010576a894 _TFC11MyApp      11AppDelegate11applicationfS0_FTCSo13UIApplication29didFinishLaunchingWithOptionsGSqGVSs10DictionaryCSo8NSObjectPSs9AnyObject____Sb + 340
      16  MyApp                               0x000000010576b660 _TToFC11MyApp        11AppDelegate11applicationfS0_FTCSo13UIApplication29didFinishLaunchingWithOptionsGSqGVSs10DictionaryCSo8NSObjectPSs9AnyObject____Sb + 560
      17  UIKit                               0x00000001064f9475 -[UIApplication _handleDelegateCallbacksWithOptions:isSuspended:restoreState:] + 234
      18  UIKit                               0x00000001064f9fbc -[UIApplication _callInitializationDelegatesForMainScene:transitionContext:] + 2463
      19  UIKit                               0x00000001064fcd2c -[UIApplication _runWithMainScene:transitionContext:completion:] + 1350
      20  UIKit                               0x00000001064fbbf2 -[UIApplication workspaceDidEndTransaction:] + 179
      21  FrontBoardServices                  0x00000001092822a3 __31-[FBSSerialQueue performAsync:]_block_invoke + 16
      22  CoreFoundation                      0x0000000105ba853c __CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__ + 12
      23  CoreFoundation                      0x0000000105b9e285 __CFRunLoopDoBlocks + 341
      24  CoreFoundation                      0x0000000105b9da43 __CFRunLoopRun + 851
      25  CoreFoundation                      0x0000000105b9d486 CFRunLoopRunSpecific + 470
      26  UIKit                               0x00000001064fb669 -[UIApplication _run] + 413
      27  UIKit                               0x00000001064fe420 UIApplicationMain + 1282
      28  MyApp                               0x000000010576bb9e top_level_code + 78
      29  MyApp                               0x000000010576bbda main + 42
      30  libdyld.dylib                       0x0000000107fcc145 start + 1
      31  ???                                 0x0000000000000001 0x0 + 1
  )
  libc++abi.dylib: terminating with uncaught exception of type NSException
  (lldb) 
  </code></pre>
  
  <p>What should I try to make this kind of relationship work in my code?</p>