oc 可变參数传递

- (id)initWithFrame:(CGRect)frame delegate:(id<SGFocusImageFrameDelegate>)delegate focusImageItems:(SGFocusImageItem *)firstItem, ...
{
    self = [super initWithFrame:frame];
    if (self) {
        NSMutableArray *imageItems = [NSMutableArray array];
        SGFocusImageItem *eachItem;
        va_list argumentList;
        if (firstItem)
        {
            [imageItems addObject: firstItem];
            va_start(argumentList, firstItem);
            while((eachItem = va_arg(argumentList, SGFocusImageItem *)))
            {
                [imageItems addObject: eachItem];
            }
            va_end(argumentList);
        }

        objc_setAssociatedObject(self, (const void *)SG_FOCUS_ITEM_ASS_KEY, imageItems, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
        _isAutoPlay = YES;
        [self setupViews];

        [self setDelegate:delegate];
    }
    return self;
}