We expect to monitor which channel the user guides to install the app from, and currently we want to monitor it through marketing links. Is there an API for managing marketing links to add or delete marketing links?

Please, how should I achieve it? I want to draw a gradient circle, the color is white, and the alpha starts to change according to the specified(0%, 10%, 30%) position. I tried CGContextDrawRadialGradient, but the effect is wrong. Below is my code and Demo. code: CGFloat colors[] = {     1, 1, 1, 0.35,     1, 1, 1, 0.10,     1, 1, 1, 0.0,   }; CGGradientRef gradient = CGGradientCreateWithColorComponents(rgb, colors, NULL, 3);     CGContextRef graCtx = UIGraphicsGetCurrentContext();     CGContextDrawRadialGradient(graCtx, gradient, self.center, 75, self.center, 100, kCGGradientDrawsBeforeStartLocation | kCGGradientDrawsAfterEndLocation); CGColorSpaceRelease(rgb); sample: