ruler.m

- (void)viewDidLoad
{
    [super viewDidLoad];
    
    NSUInteger const mmWidth = 10;
    CGSize const boundsSize = { mmWidth*10, 50 };
    UIGraphicsBeginImageContextWithOptions(boundsSize, NO, 0);
    self.view.contentMode = UIViewContentModeTop;
    [[UIColor blackColor] setFill];
    UIRectFill((CGRect) {
        0, 0,
        boundsSize.width, 0.5
    });
    for(NSUInteger x = 0; x < mmWidth*10; x += mmWidth) {
        BOOL isCmMarker = x%(mmWidth*10) == 0;
        float const width = isCmMarker ? 1.5 : 0.5;
        UIRectFill((CGRect) {
            floorf(x - width/2.0f) + 0.5f,
            0,
            width,
            isCmMarker ? 15 : 10
        });
    }
    self.view.backgroundColor = [UIColor colorWithPatternImage:UIGraphicsGetImageFromCurrentImageContext()];
    UIGraphicsEndImageContext();
}

usingpaths.m

- (void)viewDidLoad
{
    [super viewDidLoad];
    
    _rulerLayer = [CAShapeLayer new];
    _rulerLayer.lineWidth = 1;
    _rulerLayer.strokeColor = [UIColor blackColor].CGColor;
    
    _mmLayer = [CAShapeLayer new];
    _mmLayer.lineWidth = 10;
    _mmLayer.transform = CATransform3DMakeTranslation(0, _mmLayer.lineWidth/2.0f, 0);
    _mmLayer.strokeColor = _rulerLayer.strokeColor;
    _mmLayer.lineDashPattern = @[@0.5, @9.5];
    
    _cmLayer = [CAShapeLayer new];
    _cmLayer.lineWidth = 15;
    _cmLayer.transform = CATransform3DMakeTranslation(0, _cmLayer.lineWidth/2.0f, 0);
    _cmLayer.strokeColor = _rulerLayer.strokeColor;
    _cmLayer.lineDashPattern = @[@1, @99];
    
    [self.view.layer addSublayer:_rulerLayer];
    [_rulerLayer addSublayer:_mmLayer];
    [_rulerLayer addSublayer:_cmLayer];
}

- (void)viewDidLayoutSubviews
{
    UIBezierPath * const rulerPath = [UIBezierPath bezierPath];
    [rulerPath moveToPoint:(CGPoint) { 0, 100 }];
    [rulerPath addLineToPoint:(CGPoint) { self.view.bounds.size.width, 100 }];
    
    _rulerLayer.path = [[rulerPath copy] CGPath];
    _mmLayer.path = [[rulerPath copy] CGPath];
    _cmLayer.path = [[rulerPath copy] CGPath];
}