iOS---UILabel使用drawRect添加下划线

 - (void)drawRect:(CGRect)rect
 {
     [super drawRect:rect];
     CGContextRef ctx = UIGraphicsGetCurrentContext();
     CGSize fontSize =[self.text sizeWithFont:self.font
                                     forWidth:self.bounds.size.width
                                lineBreakMode:UILineBreakModeTailTruncation];


     // Get the fonts color.

     const float * colors = CGColorGetComponents(self.textColor.CGColor);
     // Sets the color to draw the line
     CGContextSetRGBStrokeColor(ctx, colors[0], colors[1], colors[2], 1.0f); // Format : RGBA

     // Line Width : make thinner or bigger if you want
     CGContextSetLineWidth(ctx, 1.0f);

     // Calculate the starting point (left) and target (right)
     CGPoint l = CGPointMake(0,
                             self.frame.size.height/2.0 +fontSize.height/2.0);

     CGPoint r = CGPointMake(fontSize.width,
                             self.frame.size.height/2.0 + fontSize.height/2.0);


     // Add Move Command to point the draw cursor to the starting point
     CGContextMoveToPoint(ctx, l.x, l.y);

     // Add Command to draw a Line
     CGContextAddLineToPoint(ctx, r.x, r.y);


     // Actually draw the line.
     CGContextStrokePath(ctx);

     // should be nothing, but who knows...
     [super drawRect:rect];

 }