Ios 尝试将非属性列表对象设置为键imgAssetURL的NSUserDefaults值

上述方法在[userDefaults setObject:arrayImgAssetURL forKey:@imgAssetURL]崩溃

方法[[GalassetLibrary sharedReference]readImagesFromGallery]；返回_block NSArray对象，并将其指定给具有值的arrayImgAssetURL。只有当我试图插入userDefault时，它才会崩溃。NSUserDefaults仅允许插入数组、数据、字符串、数字、日期、字典。那它为什么会崩溃呢？这个问题的解决方案是什么

事故日志

__block NSArray *arrayImgAssetURL = [[NSUserDefaults standardUserDefaults] objectForKey:@"imgAssetURL"];

    // if img url is not available then find image url and save to user default and
    if (!arrayImgAssetURL) {
        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^{
            arrayImgAssetURL = [[GALAssetsLibrary sharedReference] readImagesFromGallery];
            // write asset image url to user default
            NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
            [userDefaults setObject:arrayImgAssetURL
                             forKey:@"imgAssetURL"];
            [userDefaults synchronize];
        });
    }

---

arrayImgAssetURL中的对象类型是什么？NSURL或NSString？比较arrayImgAssetURL是NSARRAYTANKS kap类的一种，arrayImgAssetURL有NSURL对象，当我将其转换为NSString时，效果很好。谢谢：

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', 
reason: '*** -[NSUserDefaults setObject:forKey:]: 
attempt to insert non-property list object (
    "assets-library://asset/asset.JPG?id=E3DCD905-082D-4D0C-886E-55CDFC669D41&ext=JPG",
    "assets-library://asset/asset.JPG?id=F471F275-AD0A-489F-9330-CB8A51571087&ext=JPG",
    "assets-library://asset/asset.JPG?id=7F313D5B-CA0E-493C-9A1E-AC15BABFC741&ext=JPG",
    "assets-library://asset/asset.JPG?id=2270D5A3-0741-4278-9021-79FA89AAB6CB&ext=JPG",
    "assets-library://asset/asset.JPG?id=239747B8-0586-490E-BCF1-6BB5675D47EE&ext=JPG",
    "assets-library://asset/asset.JPG?id=882487BA-1A54-4B97-8B56-DB5409AB6262&ext=JPG",
    "assets-library://asset/asset.JPG?id=88CDC266-CE00-44AB-A24B-9630B27E2AED&ext=JPG",
    "assets-library://asset/asset.JPG?id=3B6B3C09-9839-48C2-91EA-B26691445892&ext=JPG"
) for key imgAssetURL'
*** First throw call stack:
(
    0   CoreFoundation                      0x017f21e4 __exceptionPreprocess + 180
    1   libobjc.A.dylib                     0x015718e5 objc_exception_throw + 44
    2   CoreFoundation                      0x017f1fbb +[NSException raise:format:] + 139
    3   Foundation                          0x011a4a40 -[NSUserDefaults(NSUserDefaults) setObject:forKey:] + 150
    4   FaceDetection                       0x0000296d __59-[MCAppDelegate application:didFinishLaunchingWithOptions:]_block_invoke + 237
    5   libdispatch.dylib                   0x01e377b8 _dispatch_call_block_and_release + 15
    6   libdispatch.dylib                   0x01e4c4d0 _dispatch_client_callout + 14
    7   libdispatch.dylib                   0x01e3aeb7 _dispatch_root_queue_drain + 291
    8   libdispatch.dylib                   0x01e3b127 _dispatch_worker_thread2 + 39
    9   libsystem_pthread.dylib             0x021772e3 _pthread_wqthread + 801
    10  libsystem_pthread.dylib             0x02174eea start_wqthread + 30
)
libc++abi.dylib: terminating with uncaught exception of type NSException