iOS - Convert NSArray to float array

Question

I have this an array called self.gradientArray of colors. When I print it out it looks like this:

gradientsArray: (
    "UIDeviceRGBColorSpace 0.333333 0.811765 0.768627 1",
    "UIDeviceRGBColorSpace 0.333333 0.811765 0.768627 1" )

I want to convert this array into a CGFloat array. An example is like this:

CGFloat colors [] = {
                1.0, 1.0, 1.0, 1.0,
                1.0, 0.0, 0.0, 1.0
            };

I tried this and it didn't work. I'm new to Objective-C and the syntax so please help me.

CGFloat colors [] = self.gradientArray;

I want to use the CGFloat array in making gradients like this:

CGGradientRef gradient = CGGradientCreateWithColorComponents(baseSpace, colors, NULL, 2);

enumerate objects use NSArray *stringArray = [string componentsSeparatedByString: @" "]; and do it — Prashant Tukadiya
– Prashant Tukadiya, Commented Apr 19, 2016 at 6:51
@PKT I don't think he really has an array of strings. I think he has a NSArray of UIColor objects, which, when you NSLog it, generates output much like he shared in his question. — Rob
– Rob, Commented Apr 19, 2016 at 7:07

Rob · Accepted Answer · 2016-04-19 07:03:51Z

2

The gradientsArray would appear to be an array of UIColor, in which case you could do something like:

NSArray *gradientsArray = @[[UIColor redColor], [UIColor blueColor]];

CGFloat colors[gradientsArray.count * 4];
NSInteger index = 0;
for (UIColor *color in gradientsArray) {
    CGFloat red, green, blue, alpha;
    [color getRed:&red green:&green blue:&blue alpha:&alpha];
    colors[index++] = red;
    colors[index++] = green;
    colors[index++] = blue;
    colors[index++] = alpha;
}

answered Apr 19, 2016 at 7:03

Rob

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3 Comments

imstillalive Over a year ago

Works like a charm! Thanks Rob!

Preeti Rani Over a year ago

@Rob CGFloat colors[gradientsArray.count * 4]; What does 4 represents here ??

Rob Over a year ago

The OP wanted to populate his/her CGFloat array to be supplied to CGGradientCreateWithColorComponents with four component values of each color in the gradient array, namely each color’s respective red, blue, green, and alpha values.

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