iOS rainbow colors array

Question

I am setting up an array that has a transition throughout he colors of the rainbow. Right now I've just manually entered the colors in the array but there are too many to manually type... as of now I just go from 0.25 to 0.5 to 0.75 to 1 and so on until I go from Red to green to blue and back. (see code below) how can I have the array automatically generate the colors with more than just 0.25 --> 0.5 --> 0.75 but maybe 0.05 --> 0.10 --> 0.15 --> 0.20 and so on,... here is my array:

rainbowColors = [[NSArray alloc] initWithObjects:
                     [UIColor colorWithRed:1 green:0 blue:0 alpha:1],
                     [UIColor colorWithRed:1 green:0.25 blue:0 alpha:1],
                     [UIColor colorWithRed:1 green:0.5 blue:0 alpha:1],
                     [UIColor colorWithRed:1 green:0.75 blue:0 alpha:1],
                     [UIColor colorWithRed:1 green:1 blue:0 alpha:1],
                     [UIColor colorWithRed:0.75 green:1 blue:0 alpha:1],
                     [UIColor colorWithRed:0.5 green:1 blue:0 alpha:1],
                     [UIColor colorWithRed:0.25 green:1 blue:0 alpha:1],
                     [UIColor colorWithRed:0 green:1 blue:0 alpha:1],
                     [UIColor colorWithRed:0 green:1 blue:0.25 alpha:1],
                     [UIColor colorWithRed:0 green:1 blue:0.5 alpha:1],
                     [UIColor colorWithRed:0 green:1 blue:0.75 alpha:1],
                     [UIColor colorWithRed:0 green:1 blue:1 alpha:1],
                     [UIColor colorWithRed:0 green:0.75 blue:1 alpha:1],
                     [UIColor colorWithRed:0 green:0.5 blue:1 alpha:1],
                     [UIColor colorWithRed:0 green:0.25 blue:1 alpha:1],
                     [UIColor colorWithRed:0 green:0 blue:1 alpha:1],
                     [UIColor colorWithRed:0.25 green:0 blue:1 alpha:1],
                     [UIColor colorWithRed:0.5 green:0 blue:1 alpha:1],
                     [UIColor colorWithRed:0.75 green:0 blue:1 alpha:1],
                     [UIColor colorWithRed:1 green:0 blue:1 alpha:1],
                     [UIColor colorWithRed:1 green:0 blue:0.75 alpha:1],
                     [UIColor colorWithRed:1 green:0 blue:0.5 alpha:1],
                     [UIColor colorWithRed:1 green:0 blue:0.25 alpha:1],nil];

Answer 1

Far simpler, use -[UIColor colorWithHue:saturation:brightness:alpha:], like so:

NSMutableArray *colors = [NSMutableArray array];

float INCREMENT = 0.05;
for (float hue = 0.0; hue < 1.0; hue += INCREMENT) {
    UIColor *color = [UIColor colorWithHue:hue
                                saturation:1.0
                                brightness:1.0
                                     alpha:1.0];
    [colors addObject:color];
}

This allows you to vary the hue (or color) without changing how bright the color is on the screen, which you're very likely not preserving right now. It's also far simpler to write, and far clearer to a later reader.

Answer 2

3 nested for loops and 3 variables r, g, b, and add 0.25 each time the loop occurs.