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Index › Programming Questions & Help › Syntax Questions › static class not allowing creation of new objects
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static class not allowing creation of new objects (Read 584 times)
Surgery
static class not allowing creation of new objects
Jan 18th, 2009, 9:12am  
Hi,
I have a static class that looks like this:

static class Steering {

 public static void steer(Fish obj, Vector desHeading) {
   Vector forwardVec = new Vector(cos(obj.heading), sin(obj.heading), 0);
   Vector sideVec = new Vector(forwardVec.y, -forwardVec.x, 0);
 }

}

obviously there's more, but that's the important part. I have another class called Vector that my non-static classes play nice with, but when I try to use it here I get "No enclosing instance of type SchoolingFish is accessible. Must qualify the allocation with an enclosing instance of type SchoolingFish (e.g. x.new A() where x is an instance of SchoolingFish)." SchoolingFish is the name of my sketch. Is it not possible to use non-compile-time classes in a static class?
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PhiLho 
Re: static class not allowing creation of new obje
Reply #1 - Jan 18th, 2009, 11:27am  
I am not too sure of the exact problem, scope/visibility issues are subtle...
But I think the main issue is because all classes in a sketch (.pde file) are inner classes (of a class created at run time). Static classes here have a special meaning (and are not allowed for non-nested classes).
If you want to make an utility class made only of static methods, remove the "static" before "class", and put the class in a .java file: it will be external to the main class.
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Surgery
Re: static class not allowing creation of new obje
Reply #2 - Jan 18th, 2009, 11:37am  
Well, that seemed to solve that problem, but now it's not recognizing the Fish class (which is a .pde file). It's looking like it might be easier just to rewrite my static class to not be static.
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PhiLho 
Re: static class not allowing creation of new obje
Reply #3 - Jan 18th, 2009, 1:13pm  
The Fish class is probably internal to your main (invisible) class too. You might refer to it as SchoolingFish.Fish, I think (make it public if needed, although it might be the default in Processing).
Or just drop the static keyword, indeed... Smiley
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Surgery
Re: static class not allowing creation of new obje
Reply #4 - Jan 18th, 2009, 2:20pm  
Thanks for the help. I ended up just dropping the static part and kind of faking it with something like:

Steering steering;

at the top of every class that needs to use it. Pretty much the same thing. Thanks again.
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