Processing 1.0 - Processing Discourse

We closed this forum 18 June 2010. It has served us well since 2005 as the ALPHA forum did before it from 2002 to 2005. New discussions are ongoing at the new URL http://forum.processing.org. You'll need to sign up and get a new user account. We're sorry about that inconvenience, but we think it's better in the long run. The content on this forum will remain online.

Index › Programming Questions & Help › Syntax Questions › static variables

‹ Previous Topic | Next Topic ›

Pages: 1

static variables (Read 1597 times)

Surgery YaBB Newbies Offline Posts: 18	static variables Apr 5^th, 2009, 8:49pm Hey, I was wondering if anyone knew of a good way to do static variables in processing. The usual way of just declaring it as such doesn't seem to work, I'm guessing for the same reason static methods don't work. However, I can't think of a way to fake static variables. Thanks.

clankill3r Full Member Offline Posts: 210 Netherlands	Re: static variables Reply #1 - Apr 5^th, 2009, 10:35pm what do you mean by static variables?

PhiLho

Re: static variables
Reply #2 - Apr 6^th, 2009, 3:37am

Global static variables work fine in Processing... Although their usefulness is limited since there will only one PApplet per run anyway.
Indeed, you cannot put static variables in classes in a .pde file. That's because these classes are actually nested classes, internal to the PApplet.
Somehow, you can fake them with so-called global variables (which are actually fields of the PApplet).
Or, you can declare your class in a .java file, but it brings problems of its own.

Surgery YaBB Newbies Offline Posts: 18	Re: static variables Reply #3 - Apr 6^th, 2009, 9:49am By static variables I mean a variable who's value is the same across all instances of an object. I will look into this global variable. It sounds like what I need, which is basically just a list of parameters that every class in my program can access. Thanks.

lo-fi

Re: static variables
Reply #4 - May 5^th, 2009, 11:07am

All your classes can instanciate the same static class.
Code:


class Something{
  StaticInfo staticThings;  
  Something(){
    staticThings = new StaticInfo();
  }
  void run(){
    println(staticThings.staticData1);
  }
}

static class StaticInfo {
  static String staticData1 = "static data 1";
  static String staticData2 = "static data 2";
}

polymonkey

Re: static variables
Reply #5 - May 5^th, 2009, 7:00pm

Sorry to interrupt but I'm a little confused as to why this works. I always had the belief that static fields can't be changed. They are static after all. But in this I can. What's all that about? Am I delusional? or have I been assuming a little to much all these years?

void setup()
{
Something s = new Something();
s.run();
}

class Something{
StaticInfo staticThings;
Something(){
staticThings = new StaticInfo();
}
void run(){
println(staticThings.staticData1);

staticThings.staticData1 = "hey look I can change the static"; //wtf?

println(staticThings.staticData1);
}
}

static class StaticInfo {
static String staticData1 = "static data 1";
static String staticData2 = "static data 2";
}

MattD(polymonkey)

blindfish

Re: static variables
Reply #6 - May 6^th, 2009, 3:17am

If it's any help I posted a similar question in this thread.

As for static class variables, my understanding is that regardless of how many instances of the class you create, you essentially only create one instance of the variable. Changing the value of the static variable in one instance affects the value in all other instances - so essentially it's a global variable for instances of the class. I'm still getting my head round this so not sure if my explanation is technically correct, but that seems to be what happens in practice.

A 'static final' variable however is constant and cannot be changed - it's the 'final' that makes it constant, not 'static' (though I can understand why you'd interpret it that way). The annoying thing is you can declare static final variables in a class, but you can only declare a non-final static variable in a static class, which apparently may present problems in Processing. Not sure what kind of problems though and would be interested to know more...

Where is the what if the what is in why?

Pages: 1

‹ Previous Topic | Next Topic ›