Black to White radial gradient is giving whole black screen - ios

Question

It should be very simple to create a black to white radial gradient using Core Graphics, but even after many tries I am not able to figure where I am going wrong.
I want something like this:
This is my code:
CGFloat radius = shapeRect.size.width/2.0;
CGPoint center = CGPointMake(shapeRect.origin.x+shapeRect.size.width/2, shapeRect.origin.y+shapeRect.size.height/2);
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();
CGContextRef context = CGBitmapContextCreate(NULL, shapeRect.size.width, shapeRect.size.height, 8, shapeRect.size.width*4, colorSpace, kCGImageAlphaNone);
CGFloat components[] = {0.0, 1.0};
CGFloat locations[] = {0.0, 1.0};
CGGradientRef gradient = CGGradientCreateWithColorComponents(colorSpace, components, locations, 2);
CGContextDrawRadialGradient(context, gradient, center, 10, center, radius, 0);
CGImageRef img = CGBitmapContextCreateImage(context);
[maskedView setImage:[UIImage imageWithCGImage:img]];
CGGradientRelease(gradient);
CGContextRelease(context);
CGColorSpaceRelease(colorSpace);
ShapeRect here has self.view bounds.
I am getting a whole black screen with no gradient as output.
I am using iPhone 7 simulator.
Your suggestions can save my day
Thank you.

Answer 1

Please check this snippet. You can change components and locations values to get what you want and to understand how the drawing works. Refer to CGGradientCreateWithColorComponentsdescription
#import "TestView.h"
#implementation TestView {
CGGradientRef _gradient;
}
-(void)drawRect:(CGRect)rect
{
CGFloat radius = self.frame.size.width / 2.0;
CGPoint center = CGPointMake(CGRectGetMidX(self.bounds), CGRectGetMidY(self.bounds));
CGContextRef context = UIGraphicsGetCurrentContext();
CGGradientRef gradient = [self createGradient];
CGContextDrawRadialGradient(context, gradient, center, 10, center, radius, kCGGradientDrawsBeforeStartLocation);
}
-(CGGradientRef)createGradient
{
if (!_gradient) {
CGFloat components[] = { 0.0, 1.0, 0.5, 0.5, 1.0, 0.3 };
CGFloat locations[] = { 0.0, 0.6, 1.0 };
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();
_gradient = CGGradientCreateWithColorComponents(colorSpace, components, locations, 3);
CGColorSpaceRelease(colorSpace);
}
return _gradient;
}
- (void)layoutSubviews
{
self.backgroundColor = [UIColor whiteColor];
self.layer.borderColor = [UIColor lightGrayColor].CGColor;
self.layer.borderWidth = 1.;
}
#end
Result: