ArrayList of function calls

kfrajer

Is it possible to create an ArrayList of function calls? For example, I have

void step0(){}
void step1(){}
void step2(){}
(...)
void stepN(){}

Then to create an

ArrayList<void> myFxn = new ArrayList<void>();
myFxn.add(step0);
myFxn.add(step1);
myFxn.add(step2);
myFxn.add(stepN);

Then finally

void keyPressed(){
  if(key>='a' && key<='z')
     myFxn.get(key-'a');
}

The ArrayList has a list of functions I could access in an ordered manner. Just curious if this is something that can be implemented with current tools.

Kf

GoToLoop

In Java 8, JS, Python, etc., YES! However, even though P3 is bundled w/ Java 8, the way the compilation is configured and also the incomplete pre-compiler makes the PDE incompatible w/ Java 8's latest features! =((

GoToLoop

There's still hope. A quick dirty approach is to rely on undocumented function method(): *-:)

// forum.Processing.org/two/discussion/19316/
// arraylist-of-function-calls#Item_2

// GoToLoop (2016-Nov-26)

void setup() {
  final int rnd = (int) random(3);
  method("step" + rnd);
  exit();
}

void step0() {
  println("step0");
}

void step1() {
  println("step1");
}

void step2() {
  println("step2");
}

kfrajer

Thxs. Do you mind showing a piece of code or a link showing the concept please @GoToLoop.

Kf

quark

It could be done with the current version of Processing (JAVA mode) but it is challenging and uses the Java Reflection API.

GoToLoop

A more advanced technique is to create an interface or class as a wrapper for your custom functions:

// forum.Processing.org/two/discussion/19316/
// arraylist-of-function-calls#Item_5

// GoToLoop (2016-Nov-26)

import java.util.List;
static final int QTY = 3;
final List<Step> steps = new ArrayList<Step>(QTY);

void setup() {
  noLoop();

  for (int i = 0; i < QTY; ++i) {
    final int idx = i;
    final Step step = new Step() {
      @ Override public void step() {
        println(NAME + idx);
      }
    };
    steps.add(step);
  }
}

void keyPressed() {
  final int idx = (int) random(steps.size());
  steps.get(idx).step();
}

void mousePressed() {
  keyPressed();
}

interface Step {
  String NAME = "step";
  void step();
}

GoToLoop

Of course, if we already know how many we're gonna need, a regular array offers a lesser boilerplate aesthetically code: :P

// forum.Processing.org/two/discussion/19316/
// arraylist-of-function-calls#Item_6

// GoToLoop (2016-Nov-26)

static final int QTY = 3;
final Step[] steps = new Step[QTY];

void setup() {
  noLoop();

  for (int i = 0; i < QTY; ++i) {
    final int idx = i;
    final Step step = new Step() {
      @ Override public void step() {
        println(NAME + idx);
      }
    };
    steps[i] = step;
  }
}

void keyPressed() {
  final int idx = (int) random(QTY);
  steps[idx].step();
}

void mousePressed() {
  keyPressed();
}

interface Step {
  String NAME = "step";
  void step();
}

kfrajer

Interesting @GoToLoop. I will check if it works in my code. Thanks.

@Quark what is the Java Reflection API?

Kf

GoToLoop

http://docs.Oracle.com/javase/8/docs/api/java/lang/reflect/package-summary.html#package.description

quark

This discussion demonstrates how to use reflection to execute a method whose name is stored in a string

Lord_of_the_Galaxy

Interesting... Do you have any links that would help me in learning all this? Thanks in advance.

quark

Do you have any links that would help me in learning all this?

If you mean reflection you might start here