predicateWithBlock作为ABPeoplePicker.predicateForEnablingPerson的谓词导致exception

iOS8引入了一种使用NSPredicates配置ABPeoplePicker的新方案。 我需要的不仅仅是人们启用的基本谓词，所以我尝试使用predicateWithBlock，如下所示：

- (NSPredicate *)predicateForEnablingPerson { return [NSPredicate predicateWithBlock:^BOOL(id evaluatedObject, NSDictionary *bindings) { return TRUE; // Just pass back true until we figure out why it's crashing }]; } 

关于这个没有被支持的文件中没有任何内容。 任何人都知道为什么这不起作用？

 thread #1: tid = 0x4b596e, 0x049cea6b libobjc.A.dylib`objc_exception_throw, name = 'MAINTHREAD-1412492637.228968-5', queue = 'com.apple.main-thread', stop reason = breakpoint 1.1 frame #0: 0x049cea6b libobjc.A.dylib`objc_exception_throw frame #1: 0x04e0bd1d CoreFoundation`+[NSException raise:format:] + 141 frame #2: 0x03fadf0a Foundation`-[NSBlockPredicate encodeWithCoder:] + 59 frame #3: 0x03ed9219 Foundation`-[NSXPCEncoder _encodeObject:] + 665 frame #4: 0x03eeab49 Foundation`-[NSXPCEncoder _encodeArrayOfObjects:forKey:] + 299 frame #5: 0x03ebe0a4 Foundation`-[NSDictionary(NSDictionary) encodeWithCoder:] + 1273 frame #6: 0x03ed9219 Foundation`-[NSXPCEncoder _encodeObject:] + 665 frame #7: 0x03eeab49 Foundation`-[NSXPCEncoder _encodeArrayOfObjects:forKey:] + 299 frame #8: 0x03ebe0a4 Foundation`-[NSDictionary(NSDictionary) encodeWithCoder:] + 1273 frame #9: 0x03ed9219 Foundation`-[NSXPCEncoder _encodeObject:] + 665 frame #10: 0x03ed88c6 Foundation`-[NSXPCEncoder encodeObject:forKey:] + 135 frame #11: 0x03ed9611 Foundation`-[NSXPCEncoder encodeObject:] + 48 frame #12: 0x03ecd082 Foundation`_walkAndEncodeData + 1286 frame #13: 0x03ecca8c Foundation`encodeInvocationArguments + 612 frame #14: 0x03ed93dc Foundation`-[NSXPCEncoder encodeInvocation:] + 406 frame #15: 0x03ed9219 Foundation`-[NSXPCEncoder _encodeObject:] + 665 frame #16: 0x03ed88c6 Foundation`-[NSXPCEncoder encodeObject:forKey:] + 135 frame #17: 0x03ed7c30 Foundation`-[NSXPCConnection _sendInvocation:proxyNumber:remoteInterface:withErrorHandler:timeout:userInfo:] + 2910 frame #18: 0x03ee3668 Foundation`-[NSXPCConnection _sendInvocation:proxyNumber:remoteInterface:withErrorHandler:] + 95 frame #19: 0x03ee35f9 Foundation`-[_NSXPCDistantObjectWithError forwardInvocation:] + 133 frame #20: 0x04d5c78e CoreFoundation`___forwarding___ + 478 frame #21: 0x04d5c58e CoreFoundation`__forwarding_prep_0___ + 14 frame #22: 0x017515f4 AddressBookUI`-[CNContactPickerExtensionHostContext setupWithOptions:readyBlock:] + 312 frame #23: 0x01750fca AddressBookUI`-[CNContactPickerHostViewController setupWithOptions:readyBlock:] + 166 frame #24: 0x0166f4e5 AddressBookUI`-[CNContactPicker _setupViewController] + 1179 frame #25: 0x0166f024 AddressBookUI`-[CNContactPicker _setViewController:] + 447 frame #26: 0x0166f9a1 AddressBookUI`__41-[CNContactPicker _prepareViewController]_block_invoke116 + 72 frame #27: 0x01750ddc AddressBookUI`__55+[CNContactPickerHostViewController getViewController:]_block_invoke + 340 frame #28: 0x0322167e UIKit`__117-[NSExtension(UIViewControllerAdditions) instantiateViewControllerWithInputItems:listenerEndpoint:connectionHandler:]_block_invoke_3 + 129 frame #29: 0x033723aa UIKit`__124+[_UIRemoteViewController _requestViewController:traitCollection:fromServiceWithBundleIdentifier:service:connectionHandler:]_block_invoke_2 + 107 frame #30: 0x0528e41a libdispatch.dylib`_dispatch_call_block_and_release + 15 frame #31: 0x052aee1f libdispatch.dylib`_dispatch_client_callout + 14 frame #32: 0x05295981 libdispatch.dylib`_dispatch_main_queue_callback_4CF + 610 frame #33: 0x04d65f3e CoreFoundation`__CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 14 frame #34: 0x04d24d40 CoreFoundation`__CFRunLoopRun + 2256 frame #35: 0x04d241ab CoreFoundation`CFRunLoopRunSpecific + 443 frame #36: 0x04d23fdb CoreFoundation`CFRunLoopRunInMode + 123 frame #37: 0x0661d24f GraphicsServices`GSEventRunModal + 192 frame #38: 0x0661d08c GraphicsServices`GSEventRun + 104 frame #39: 0x02c8de16 UIKit`UIApplicationMain + 1526 * frame #40: 0x00002775 SmartRoam`main(argc=3, argv=0xbfffe4a4) + 565 at main.m:42 frame #41: 0x052daac9 libdyld.dylib`start + 1