UIView 子类 initWithFrame 没有被调用？

我有一个自定义 UIView 子类。在 IB 中，我指定了一个“占位符”UIView 并将该类设置为我的类名。我对 drawRect 方法的重写正在工作，并且背景着色正确，但 initWithFrame 没有触发。为什么？

- (id)initWithFrame:(CGRect)frame {
    NSLog(@"initWithFrame");
    if ((self = [super initWithFrame:frame])) {
        noteTextFont = [[UIFont boldSystemFontOfSize:12] retain];
    }
    return self;
}

- (void)drawRect:(CGRect)rect {
    [super drawRect:rect];
    CGContextRef context = UIGraphicsGetCurrentContext();

    UIColor *backgroundColor = [UIColor blackColor];
    [backgroundColor set];
    CGContextFillRect(context, rect);

    UIColor *labelColor = [UIColor lightGrayColor];
    [labelColor set];
    [notificationLabel drawInRect:CGRectMake(44, 18, rect.size.width-20, rect.size.height) withFont:noteTextFont lineBreakMode:UILineBreakModeTailTruncation];

    [self setNeedsLayout];
}

从笔尖加载的东西是用-(id)initWithCoder:(NSCoder*)coder