Processing 1.0 - Processing Discourse - How to: delete object, make an array of objects

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Index › Programming Questions & Help › Syntax Questions › How to: delete object, make an array of objects

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How to: delete object, make an array of objects (Read 6291 times)

cosmin

How to: delete object, make an array of objects
Jun 4^th, 2005, 9:42pm

I'm coming from actionscript, so the java syntax is a little foreign to me, so excuse my noobness. I just made a class of dots/particles that goes like this:

Code:


class MRect { 
  float xpos; // rect xposition 
  float ypos ; // rect yposition 
  float vx=0; //viteza pe orizontala
  float vy=0; //viteza pe verticala
  int col = 255;
  float damping; // damping of the movement 
 
  MRect(int ix, int iy, float idamping) { 
    xpos = ix; 
    ypos = iy; 
    damping = idamping; 
    println("wooohoo");
  } 

  void display() { 
    col -= 1;
    fill(col);

    vx += random(2) -1;
    vy += random(2) -1;
    vx *= damping;
    vy *= damping;
    xpos += vx;
    ypos += vy;
    rect(xpos, ypos, 1,1); 
  }
}

in DRAW I just keep calling
r1.display();
r2.display();

The FIRST question is, how do I get r1 and r2 to be actually stored in an array so I can do a for loop through them all ?

And the SECOND q, how can I remove an object from memory ? I want to remove them when (col<5).

Thx

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cosmin

Re: How to: delete object, make an array of object
Reply #1 - Jun 4^th, 2005, 9:44pm

And here's the entire code if you need it ...

Code:


MRect r1, r2, r3, r4; 
 
void setup(){ 
  size(500, 400); 
  fill(255); 
  noStroke(); 
  float damping = .98;
  r1 = new MRect(100,100,damping); 
  r2 = new MRect(200,200,damping); 
} 
 
 
 
 
void draw() { 
  background(0); 
  
  r1.display(); 
  r2.display(); 

} 
 
 
 
 
class MRect { 
  float xpos; // rect xposition 
  float ypos ; // rect yposition 
  float vx=0; //viteza pe orizontala
  float vy=0; //viteza pe verticala
  int col = 255;
  float damping; // damping of the movement 
 
  MRect(int ix, int iy, float idamping) { 
    xpos = ix; 
    ypos = iy; 
    damping = idamping; 
    println("wooohoo");
  } 
  void display() { 
    col -= 1;
    fill(col);

    vx += random(2) -1;
    vy += random(2) -1;
    vx *= damping;
    vy *= damping;
    xpos += vx;
    ypos += vy;
    rect(xpos, ypos, 1,1); 
  }

}

http://10megatons.com

seltar

Re: How to: delete object, make an array of object
Reply #2 - Jun 4^th, 2005, 10:01pm

Code:


MRect [] r;
void setup()
{
r = new MRect[arraysize];
for(int i = 0; i < r.length; i++)
 r[i] = new MRect(100,100,damping);
}
void draw()
{
for(int i = 0; i < r.length; i++)
 r[i].render();
}

something like that.. allthough now all the rects end up in 100,100, so you might want to multiply y with i, or something

good luck

-seltar

-seltar

I'm bored, therefore I program
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cosmin Full Member Offline Posts: 103	Re: How to: delete object, make an array of object Reply #3 - Jun 4^th, 2005, 10:06pm Aha. Thank you. It worked, I was close Now, how do I remove an object from memory, because when it gets to about 1500 it starts to crawl ?
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seltar

Re: How to: delete object, make an array of object
Reply #4 - Jun 4^th, 2005, 10:08pm

that part i havn't figured out.. so what i do, is reuse the objects that i'm supposed to delete.. first give them a value of alive, then set alive to false when you want to delete it, then loop through the array searching for rects which aren't alive, and reassigning new variables to them, and setting them back to alive..

hope this gives you some pointers..

I'm bored, therefore I program
http://seltar.org > seltar's special place
http://snippet.seltar.org > seltar's snippet palace
http://libraries.seltar.org > seltar's libraries

cosmin Full Member Offline Posts: 103	Re: How to: delete object, make an array of object Reply #5 - Jun 4^th, 2005, 10:44pm Hmm, that kinda sucks ...
	http://10megatons.com

cosmin Full Member Offline Posts: 103	Re: How to: delete object, make an array of object Reply #6 - Jun 4^th, 2005, 10:45pm Nou your answer the fact that I can't dele objects, it gets a little messy ...
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seltar

Re: How to: delete object, make an array of object
Reply #7 - Jun 4^th, 2005, 11:27pm

http://forum.java.sun.com/thread.jspa?threadID=526359&messageID=2525736
Lots of info there..
---
Setting an object reference to "null" tells the garbage collector that at least this one reference to the object is no longer needed. Once all references to an object are cleared, the garbage collector is free to reclaim that space.
---
When explicit nulling is helpful
http://www-106.ibm.com/developerworks/java/library/j-perf08273.html
---
Why explicit calls to gc() and explicit nulls may not be such a great idea.
---

I'm bored, therefore I program
http://seltar.org > seltar's special place
http://snippet.seltar.org > seltar's snippet palace
http://libraries.seltar.org > seltar's libraries

cosmin

Re: How to: delete object, make an array of object
Reply #8 - Jun 6^th, 2005, 11:49pm

assigning null to anything doesn't work, meaning that I get an error. I'm stuck, seems weird how I can't tell something that it's not needed anymore. I could prolly get away with about an hour of running this sketch, but I'd like to run it A LOT, I'm gonna have to do some testing/experimenting, but it doesn't look good without some way of telling objects to die.

But thanks for your help so far, I doubt I'd have gotten so far without assistance.

http://10megatons.com

cosmin

Re: How to: delete object, make an array of object
Reply #9 - Jun 7^th, 2005, 12:00am

Now I have this:

Code:


void draw() { 
  background(0); 

  for (int i=0;i<num;i++){
	  arr[i].update(); 
  }
} 

void mouseMoved(){
	arr[pos] = new MRect(mouseX, mouseY);
	pos++;
	num = max(pos, num);
	if (pos>200) pos=0;
}



 
class MRect { 
  float xpos; // rect xposition 
  float ypos ; // rect yposition 
  float vx=0; //viteza pe orizontala
  float vy=0; //viteza pe verticala
  boolean alive = true;
  int col = 255;
 
  MRect(int ix, int iy) { 
    xpos = ix; 
    ypos = iy; 
  } 


  void update() { 
  if (alive){
    col -= 5;
    if (col<5) alive=false;
    fill(col);

    vx = (vx+random(2) -1)*damping;
    vy = (vy+ random(2) -1)*damping;
    xpos += vx;
    ypos += vy;
    rect(xpos, ypos, 1,1); 
  }
  }

}

I wonder if the garbage collector understands the fact that the objects that I'm overwriting (by making pos=0 if pos>200) are no longer reachable and frees the memory ...

http://10megatons.com

cosmin Full Member Offline Posts: 103	Re: How to: delete object, make an array of object Reply #10 - Jun 7^th, 2005, 12:23am Wooo, it works !! This garbage collector seems smart I left it running for a while and the memory is still the same, very cool.
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seltar Senior Member Offline Posts: 475	Re: How to: delete object, make an array of object Reply #11 - Jun 7^th, 2005, 2:36am Nice now we know.. until next-time, my fellow programmer..
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mflux Senior Member Offline Posts: 388	Re: How to: delete object, make an array of object Reply #12 - Jun 7^th, 2005, 4:43am yup! :] setting pointers that point to your objects to null and going out of scope makes them go bye bye. so easy. now I have a question that needs asking.. which I will post in a new thread!
	Portfolio

cosmin Full Member Offline Posts: 103	Re: How to: delete object, make an array of object Reply #13 - Jun 7^th, 2005, 12:15pm yeah, I'm not actually nulling them, I'm just pretending they never existed, by making them point to a new object. Apparently gc() sees that and cleans up the memory. Code: arr[pos] = new MRect(mouseX, mouseY); pos++; if (pos>200) pos=0;
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Markavian

Re: How to: delete object, make an array of object
Reply #14 - Jun 7^th, 2005, 10:30pm

No, technically you're overwriting them.

The whole point of setting up the MRect[] array is to reserve space in memory for MRect objects. So when you assign a new MRect object a position in the array you are replacing the memory space of the previous object.

As I understand it, the array represents the reserved memory space, not references to objects, thats why you can only have a single type of data in an array.

Edit: After reading Amoeba's comments and the links provided I concede my view above is incorrect. Thanks for the info amoeba

« Last Edit: Jun 9^th, 2005, 6:53am by Markavian »

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