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Topic: communication between objects (Read 329 times) |
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st33d
 
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communication between objects
« on: Sep 27th, 2004, 10:13pm » |
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I've recently put together my first object and now I'm trying to break down my code into more objects that I can utilise later.
I'm trying to make a plotter and a recorder. The plotter asks the recorder to remember an expanding stack of co-ordinates. The plotter will also need to access the recorder's memory. My example of how I thought this should be expressed is below.
Code:
memory mem = new memory (100.0,100.0);
foriegnObject obj = new foriegnObject (100.0,100.0);
void loop() {
if (mousePressed){
obj.inc();
obj.stack();
println(obj.x+" "+obj.y);
}
}//loop;
class memory{
float [] xs=new float[1];
float [] ys=new float[1];
memory (float xtt,float ytt){
xs[0]=xtt;
ys[0]=xtt;
}
void extendx(float newx) {
float[] tempx = new float[xs.length + 1];
System.arraycopy(xs, 0, tempx, 0, xs.length);
tempx[xs.length] = newx;
xs = tempx;
}
void extendy(float newy) {
float[] tempy = new float[ys.length + 1];
System.arraycopy(ys, 0, tempy, 0, ys.length);
tempy[ys.length] = newy;
ys = tempy;
}
}//memory;
class foriegnObject {
float x;
float y;
foriegnObject ( float xt, float yt ) {
x=xt;
y=yt;
}
void stack(){
mem.extendx(xs[mem.xs.length-1]);
mem.extendy(ys[mem.ys.length-1]);
mem.xs[mem.xs.length-1]=x;
mem.ys[mem.ys.length-1]=y;
}//stack;
void inc(){
x++;
y++;
}//inc;
}//foreignObject;
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I've only tried to access an object from outside before, so I'm not sure if I've simply phrased this wrong or what. I'd appreciate it if anyone has a few moments to set me straight.
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I could murder a pint.
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fjen
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Re: communication between objects
« Reply #1 on: Sep 27th, 2004, 10:33pm » |
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Code:
// <-- changes are marked like this
memory mem = new memory (100.0,100.0);
foriegnObject obj = new foriegnObject (100.0,100.0, mem); // <--
void loop() {
if (mousePressed){
obj.inc();
obj.stack();
println(obj.x+" "+obj.y);
}
}//loop;
class memory{
float [] xs=new float[1];
float [] ys=new float[1];
memory (float xtt,float ytt){
xs[0]=xtt;
ys[0]=xtt;
}
void extendx(float newx) {
float[] tempx = new float[xs.length + 1];
System.arraycopy(xs, 0, tempx, 0, xs.length);
tempx[xs.length] = newx;
xs = tempx;
}
void extendy(float newy) {
float[] tempy = new float[ys.length + 1];
System.arraycopy(ys, 0, tempy, 0, ys.length);
tempy[ys.length] = newy;
ys = tempy;
}
}//memory;
class foriegnObject {
float x;
float y;
memory mem; // <--
// <--
foriegnObject ( float xt, float yt, memory m ) {
x=xt;
y=yt;
mem = m; // <--
}
void stack(){
mem.extendx(mem.xs[mem.xs.length-1]); // <--
mem.extendy(mem.ys[mem.ys.length-1]); // <--
mem.xs[mem.xs.length-1]=x;
mem.ys[mem.ys.length-1]=y;
}//stack;
void inc(){
x++;
y++;
}//inc;
}//foreignObject;
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here you go ...
an object (an instance of a class) does not know the variables that exsist out of it's scope (not inside it's { }) (see link below). to access variables on the outside you can pass a reference to another object to it (like i did with memory). this reference can then be used inside the class to access data on the outside.
java variables (scroll down to "scope"):
http://java.about.com/library/weekly/aa_vars1.htm
http://www.particle.kth.se/~lindsey/JavaCourse/Book/Supplements/Chapter0 5/scope.html
/F
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| « Last Edit: Sep 28th, 2004, 12:28am by fjen » |
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fjen
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Re: communication between objects
« Reply #2 on: Sep 28th, 2004, 12:30am » |
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sorry my first explanation was somewhat confusing. .. hopefully it's a little better now ..
/F
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st33d
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Re: communication between objects
« Reply #3 on: Sep 30th, 2004, 11:14pm » |
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Thanks. I knew about the hermetic nature of objects but I hadn't actually had to deal with it what with using just the one object. I think I've just got dodgy equations and poor typing to deal with now.
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I could murder a pint.
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