how to make a gradient border of UIView?

Question

I want to make a gradient border of view like the following picture:

but I don\'t know how d

Answer 1

objective-c version of Christos Hadjikyriacou's answer

  @implementation CALayer(Border)

-(void) addGradientBorder {

CAGradientLayer *gradientLayer =  [[CAGradientLayer alloc] init];
gradientLayer.frame = CGRectMake(0, 0, self.bounds.size.width, self.bounds.size.height);
gradientLayer.startPoint = CGPointMake(0.0, 0.5);
gradientLayer.endPoint = CGPointMake(1.0, 0.5);
gradientLayer.colors = @[(id)[UIColor redColor].CGColor, (id)[UIColor blueColor].CGColor];

CAShapeLayer *shapeLayer =[[CAShapeLayer alloc] init];
shapeLayer.lineWidth = 0.5;
shapeLayer.path = [UIBezierPath bezierPathWithRect:self.bounds].CGPath;
shapeLayer.fillColor = nil;
shapeLayer.strokeColor = [UIColor blackColor].CGColor;
gradientLayer.mask = shapeLayer;
[self addSublayer : gradientLayer];
}
@end