为什么我的unicode角色看起来与我的期望不同？

我正在向棋盘添加棋子,我正在使用他们的unicode角色.但是,我希望它们看起来像来自维基百科的这些:

但它们显示如下:

我用来显示这些代码的代码如下:

- (void)drawRect:(CGRect)rect
{
    NSMutableParagraphStyle *textStyle = [[NSMutableParagraphStyle defaultParagraphStyle] mutableCopy];
    textStyle.alignment = NSTextAlignmentCenter;

    NSDictionary *attrs =
    @{ NSForegroundColorAttributeName : [UIColor blackColor],
       NSFontAttributeName:[UIFont fontWithName:@"HelveticaNeue" size:_squareSize],
       NSParagraphStyleAttributeName:textStyle
       };

    [[self getStringForValue:_squareValue] drawInRect:rect withAttributes:attrs];

}

- (NSString*)getStringForValue:(int)value
{
    NSString* piece;

    switch (_squareValue) {
            // white pieces
        case 1:
            piece = @"\u2659";
            break;

        case 2:
            piece = @"\u2658";
            break;

        case 3:
            piece = @"\u2654";
            break;

        case 5:
            piece = @"\u2657";
            break;

        case 6:
            piece = @"\u2656";
            break;

        case 7:
            piece = @"\u2655";
            break;

            // black pieces
        case 9:
            piece = @"\u265F";
            break;

        case 10:
            piece = @"\u265E";
            break;

        case 11:
            piece = @"\u265A";
            break;

        case 13:
            piece = @"\u265D";
            break;

        case 14:
            piece = @"\u265C";
            break;

        case 15:
            piece = @"\u265B";
            break;

        default:
            piece = @"";
            break;
    }
    return piece;
}

为什么这些作品与维基百科不同？这是字体吗？如果是这样,我应该使用哪种字体？我尝试了几种字体,但每次字符看起来都一样.