Why can't I serialize this data?

I want to serialize an array and an integer. When I save only the integer, it works. When I add the array, it fails.

    NSArray *tempArray = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *docsPath = [tempArray objectAtIndex:0];

    tempArray = nil;
    tempArray = [NSArray arrayWithObjects:
                 ( (someOtherArray != nil) ? (id) someOtherArray : [NSNull null] ),
                 [NSNumber numberWithInt:someIntValue],
                 nil];

    NSString *filePath = [NSString stringWithFormat:@"%@/%@.plist", docsPath, kDataFilename];
    NSString *errString;
    NSData *serializedStrings= [NSPropertyListSerialization
                                dataFromPropertyList:tempArray
                                format:NSPropertyListBinaryFormat_v1_0
                                errorDescription:&errString];
    if( errString != nil ) {
        NSLog(@"SaveData NSpropertyListSerialization error: %@", [errString description]);
        [errString release];
    }

    // returns NO
    BOOL success = [serializedStrings writeToFile:filePath atomically:YES];

The array may be nil so I do a check for that first. I also tried [NSNumber numberWithInt:0] instead of [NSNull null] just to see if it would work instead of null, but it didn't.

I also开发者_运维知识库 get: NSpropertyListSerialization error: Property list invalid for format

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You can't store +[NSNull null] in a plist. You need a workaround like a placeholder value (even though NSNull is itself a placeholder value...)