Quartz2d and Instance Method

I am newbie on IOS developing. I try to write my own custom class to do some 2d stuff. (TwoDOperations.h and TwoDOperations.m). Below are my files.

--------TwoDOperations.h------

@interface TwoDOperations : UIView
- (void)drawRect:(CGRect)rect withscene:(UIViewController *)sender;
- (void)drawRectV2:(CGRect)rect;
-(instancetype)init;
@end

--------TwoDOperations.m------

#import "TwoDOperations.h"

@implementation TwoDOperations

-(instancetype)init{
    self=[super init];
    if (self)
    {
    }
    return self;
}



- (void)drawRect:(CGRect)rect withscene:(UIViewController *)sender{
    UIView *myBox  = [[UIView alloc] initWithFrame:CGRectMake(10, 20, 300, 10)];
    myBox.backgroundColor = [UIColor lightGrayColor];
    [sender.view addSubview:myBox];
    }

- (void)drawRectV2:(CGRect)rect{
    UIBezierPath *circle = [UIBezierPath
                            bezierPathWithOvalInRect:CGRectMake(0, 0, 200, 200)];

    UIGraphicsBeginImageContext(CGSizeMake(200, 200));


    CGContextRef context = UIGraphicsGetCurrentContext();

    CGContextSetStrokeColorWithColor(context, [UIColor blueColor].CGColor);
    CGContextSetFillColorWithColor(context, [UIColor lightGrayColor].CGColor);
    [circle fill];
    [circle stroke];
   }

@end

as you see I have two methods to do some 2d things.

and my main methods like this

TwoDOperations  *twoD = [[TwoDOperations alloc]init];

CGRect  rect = CGRectMake(10,10,10,10);
[twoD drawRect:rect withscene:self];
[twoD drawRectV2:rect];

(I know rect is not used for now)

when I use <twoD drawRect:rect with scene:self> it is successfully drawing. I can draw a rectangle. But when I use <twoD drawRectV2:rect> it is nothing. It doesn't draw anything? I check in debug mode and I find context is not null. I ask simply why?