Gradient Layer over ImageView reuse - ios

Question

Within my 'cellForRowAtIndexPath' I have the following code to populate the image (async) and apply a custom gradient
This worked fine, until I added a custom colour per cell. What it's currently doing is recycling the previous colour rather than applying a new one - this is presumably due to the following line which will skip the gradient code once applied to each cell:
if(!cell.gradientMask){
However, if I comment this out, the colours work but the gradient on each cell will stack up as a new layer is added each time (see existing issue)
I presume I need to remove the gradientLayer on each iteration, is that the best approach or perhaps I need to subclass the UIImageView?
if (!cell.gradientMask) {
gradientMask = [CAGradientLayer layer];
gradientMask.frame = cell.eventImage.layer.bounds;
gradientMask.startPoint = CGPointMake(0.5, 0.2);
gradientMask.endPoint = CGPointMake(0.5, 1.0);
/* THIS COLOUR CHANGES FOR EACH CELL */
gradientMask.colors = [NSArray arrayWithObjects:
(id)[[UIColor colorWithRed:0.0f green:0.0f blue:1.0f alpha:0.0f] CGColor],
(id)[[UIColor colorWithRed:0.0f green:0.0f blue:1.0f alpha:1.0f] CGColor],nil];
[cell.eventImage.layer insertSublayer:gradientMask atIndex:0];
cell.gradientMask = gradientMask;
}

Answer 1

You need to set the colors outside the block which creates the gradientMask:
if (!cell.gradientMask) { //Operations that need to be carried out only ONCE are put inside this block
gradientMask = [CAGradientLayer layer];
gradientMask.frame = cell.eventImage.layer.bounds;
gradientMask.startPoint = CGPointMake(0.5, 0.2);
gradientMask.endPoint = CGPointMake(0.5, 1.0);
[cell.eventImage.layer insertSublayer:gradientMask atIndex:0];
cell.gradientMask = gradientMask;
}
//Operations that need to be carried out again and again are outside the block
if (condition1)
{
cell.gradientMask.colors = [NSArray arrayWithObjects:
(id)[[UIColor colorWithRed:0.0f green:0.0f blue:1.0f alpha:0.0f] CGColor],
(id)[[UIColor colorWithRed:0.0f green:0.0f blue:1.0f alpha:1.0f] CGColor],nil];
}
else
{
cell.gradientMask.colors = [NSArray arrayWithObjects:
(id)[[UIColor colorWithRed:0.0f green:1.0f blue:0.0f alpha:0.0f] CGColor],
(id)[[UIColor colorWithRed:0.0f green:1.0f blue:0.0f alpha:1.0f] CGColor],nil];
}