Objective c 2D gradient - objective-c

Question

I need to make at 2D gradient. I have the first part of it make a gradient vertical direction from a color to a clear color:
+ (void)addFadeout:(UIView *) view withColor:(UIColor *)color {
UIColor * halfClearColor = [color colorWithAlphaComponent:0];
CALayer *layer = view.layer;
layer.masksToBounds = YES;
CAGradientLayer *shineLayer = [CAGradientLayer layer];
shineLayer.frame = layer.bounds;
shineLayer.colors = #[
(id)color.CGColor,
(id)halfClearColor.CGColor];
shineLayer.locations = #[
[NSNumber numberWithFloat:0.0f],
[NSNumber numberWithFloat:1.0f]];
[view.layer insertSublayer:shineLayer atIndex:0];
}
But I also need to be able to add multiple colors in the horizontal direction where they either fade together and is shown separately(still with the vertical gradient). I know I could just add them besides each other but that is not what I am looking for.. How would you do it?
It might be something like this but I can't seem to connect the parts:
http://cupsofcocoa.com/tag/gradient/
https://developer.apple.com/library/mac/#documentation/graphicsimaging/conceptual/drawingwithquartz2d/dq_shadings/dq_shadings.html
Edit 1:
This is what I got now:
It might be unclear what I wanted. I also want a gradient along the x-axis between multiple colors. So what I got combined with something like this: (to replace the red color)
Solution:
+ (void)addFadeout:(UIView *) view withColors:(NSArray *)colors { //CGColors
UIColor * someColor = [UIColor colorWithCGColor:((__bridge CGColorRef)[colors lastObject])];//only alpha channel used with more than one color
UIColor * halfClearColor = [someColor colorWithAlphaComponent:0];
CALayer *layer = view.layer;
layer.masksToBounds = YES;
CAGradientLayer *transparencyLayer = [CAGradientLayer layer];
transparencyLayer.frame = layer.bounds;
transparencyLayer.colors = #[
(id)someColor.CGColor,
(id)halfClearColor.CGColor];
transparencyLayer.locations = #[
[NSNumber numberWithFloat:0.0f],
[NSNumber numberWithFloat:1.0f]];
if(colors.count > 1){
CAGradientLayer * multiColoredLayer = [self getMultiColoredLayerWithColors:colors inLayer:layer];
multiColoredLayer.mask = transparencyLayer;
[view.layer insertSublayer:multiColoredLayer atIndex:0];
}
else{
[view.layer insertSublayer:transparencyLayer atIndex:0];
}
}
+ (CAGradientLayer *)getMultiColoredLayerWithColors:(NSArray *)colors inLayer:(CALayer *)layer{ //CGColors
CAGradientLayer *gradientLayer = [CAGradientLayer layer];
gradientLayer.frame = layer.bounds;
gradientLayer.colors = colors;
gradientLayer.startPoint = CGPointMake(0, 0.5);
gradientLayer.endPoint = CGPointMake(1.0, 0.5);
return gradientLayer;
}

Answer 1

You need to use 2 of 'something' as gradients can only be drawn in a single direction at a time. You could do it with 2 CAGradientLayers, one behind the other (or one as a sublayer of the other). Or, you could do it with 2 CGGradients, both drawn into the same context.
From your comment, you want to alpha mask. The best way to apply the 'top' layer with transparency is by setting it as the mask of the 'bottom' layer:
CAGradientLayer *colorLayer = ...;
CAGradientLayer *transparencyLayer = ...;
colorLayer.mask = transparencyLayer;
In this case, any colour in the transparencyLayer is ignored and only the alpha values are used.