# Return object in method and use its functions

**URL:** <https://discourse.processing.org/t/return-object-in-method-and-use-its-functions/22140>\
**Category:** Coding Questions\
**Created:** [June 24, 2020, 8:23pm UTC](https://discourse.processing.org/t/return-object-in-method-and-use-its-functions/22140 "2020-06-24T20:23:36Z")\
**Posts on this page:** 7\
**Page:** 1

<div class="post-metadata">

**Author:** ![Alphaprot](https://avatars.discourse-cdn.com/v4/letter/a/ee7513/32.png) [@Alphaprot](https://discourse.processing.org/u/Alphaprot)\
**Post date:** [June 24, 2020, 8:23pm UTC](https://discourse.processing.org/t/return-object-in-method-and-use-its-functions/22140/1 "2020-06-24T20:23:36Z")

</div>

Hey folks,

I am trying to get interactions done in a little fisicia-based game of mine. Goal is a method/function, that returns the nearest type of objectType X (passed as an argument) in a given interaction distance (say the player can only interact with objects in a +/- 30/30 square box around him).

This method looks currently like this:

```auto
Object fetchNearestObject(String objectType) { //return coordinates of nearest object of type 'objectType' inside action radius 
  ArrayList nearestObjects = new ArrayList();
  while (nearestObjects.get(0).getClass().getSimpleName() != objectType ) {
    for (float extentX=0; extentX<=actionRadius; extentX++) {
      for (float extentY=0; extentY<=actionRadius; extentY++) {
        ArrayList temp1 = new ArrayList();
        ArrayList temp2 = new ArrayList();
        temp1 = world.getBodies((player.xPos + extentX), (player.yPos + extentY), true);
        temp2 = world.getBodies((player.xPos - extentX), (player.yPos - extentY), true);
        if (temp1.size() != 0) {
          for (int i=0; i<temp1.size(); i++) {
            if (temp1.get(i).getClass().getSimpleName() == objectType) {
              nearestObjects.add(temp1.get(i));
              println("Found " + temp1.get(i));
            }
          }
        }
        if (temp2.size() != 0) { 
          for (int i=0; i<temp2.size(); i++) {
            if (temp2.get(i).getClass().getSimpleName() == objectType) {
              nearestObjects.add(temp2.get(i));
              println("Found " + temp2.get(i));
            }
          }
        }
      }
    }
  }
  return nearestObjects.get(0);

```

As you can see, it returns an object type (am I doing this right? 🤔)

Now I’m using this method call in other interaction functions, e.g. in the player method `void climb`

```auto
  void climb(String direction) {
    if (fetchNearestObject("Ladder").getClass().getSimpleName() == "Ladder") {// check if ladder is in range and center player according to ladder base/top
      if (fetchNearestObject("Ladder").topAnchor.get(1) >= this.yPos-actionRadius) {
        this.xPos = fetchNearestObject("Ladder").topAnchor.get(0);
      } else if (fetchNearestObject("Ladder").bottomAnchor.get(1) >= this.yPos+actionRadius) {
        this.xPos = fetchNearestObject("Ladder").bottomAnchor.get(0);
      }

      if (direction == "up") {
        yPos = yPos++;
      } else if (direction == "down") {
        yPos = yPos--;
      }
    }
  }

```

But it seems like JAVA doesn’t like this way of object passing (I am far from being a skilled JAVA developer; I know just the basics). The error raised is basically `global variable topAnchor does not exist`, same goes for any method like the getX()-function inherited to the “Ladder” class by fisica’s FBody class.

Hope you can help me with that - how can I access the methods and local variables of an object returned by my `fetchNearestObject()` function?

Kind regards from Germany  
Yannik

---

<div class="post-metadata">

**Author:** ![Chrisir](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/chrisir/32/45_2.png) [@Chrisir](https://discourse.processing.org/u/Chrisir)\
**Post date:** [June 25, 2020, 9:55am UTC](https://discourse.processing.org/t/return-object-in-method-and-use-its-functions/22140/2 "2020-06-25T09:55:38Z")

</div>

> [@Alphaprot](#):
>
> `Object fetchNearestObject(String objectType) { //return coordinates of nearest object of type 'objectType' inside action radius `

Object is a Java keyword. Did you name your class Object as well? Not a good idea.

When your class has a decent name like ObjectTypeX and you want to return ObjectTypeX, tell processing that this is so:

`ObjectTypeX fetchNearestObject(String objectType) { `

**Remark**

By the way you can declare an ArrayList like this: `ArrayList<ObjectTypeX> list = new ArrayList();`

**Remark**

This

```auto
... .getSimpleName() != objectType

```

won’t work, you can’t use == with String.

Use equals instead

```auto
if ( ! ... .getSimpleName().equals ( objectType ) )

```

**Remark**

```auto
        temp1 = world.getBodies((player.xPos + extentX), (player.yPos + extentY), true);
        temp2 = world.getBodies((player.xPos - extentX), (player.yPos - extentY), true);
        

```

I kind of understand what you are doing here but with using + and again + in the first line and - and - in the second, you would pick the right and down section with the first line, and the left and up section with the 2nd, but not the other 2 sections.

So either say

```auto
                             // minus 
for (float extentX= -actionRadius; extentX<=actionRadius; extentX++) {

```

OR look at dist() for the distance between object (center) and player (center)

Chrisir

---

<div class="post-metadata">

**Author:** ![Alphaprot](https://avatars.discourse-cdn.com/v4/letter/a/ee7513/32.png) [@Alphaprot](https://discourse.processing.org/u/Alphaprot)\
**Post date:** [June 25, 2020, 12:16pm UTC](https://discourse.processing.org/t/return-object-in-method-and-use-its-functions/22140/3 "2020-06-25T12:16:42Z")

</div>

Hey Chrisir,  
thanks for your reply.

* * *

I thought using Object as the method type would be sufficient as I cannot really predict what kind of object is being returned.

I have multiple classes (e.g. class `Ladder`, class `Door`, …), which all inherit from/extend to the primary class FBody (a native fisica-class).  
Using FBody as the object type won’t work - and using the distinctive class type would void the idea of returning **any** object of the all possible classes (e.g. you could only return a ` Ladder` object, if the method type is `Ladder`).

Is there any way to return any of my class objects? If you pass the String “Ladder” to the method, it should return a `Ladder` type, if you pass “Door”, it should return a `Door` type etc. - and if possible all inside one function.

Other idea would be: return a FBody with the fisica-function `getBody()` and only use the coordinates gathered before that. Toss them into the `getBody()` function. And return an FBody.

* * *

What do you mean with your second remark? Perhaps “can’t declare like this”?

* * *

Regarding the two nested for-loops: it should work as expected, since the first loop (extentX) starts at 0 and then all extentY-values from 0 - 30 (actionRadius) are checked (temp1) and then from -30 - 0). After this, the extentX gets incremented by 1 and the second for loop checks in both directions (again up 30 and down 30).  
Generally speaking: start at the center `x = player.xPos`, check horizontally +30 and -30 from `player.yPos`. After that, do the same horizontal-check one x-step left and right of the `player.xPos`, then do the same two x-steps left and right of the `player.xPos`, … , do the same 30 x-steps left and right of the `player.xPos`  
The result should be a fully covered square of 30 pixels in each direction.

The only “not-so-great-thing” about this idea is of course that you might fetch a false-positive nearest object by doing so. E.g. one object that is 30 pixels below the player, but shares the same xPos will be returned, while another object is just 1 pixel right next to the player in x-direction, but get’s ignored. But I could live with that; objects of the same kind won’t be that tightly spaced. ^^

* * *

Thanks for some tips (especially the equals()-method for strings 🙂

Kind regards and thanks for your patience  
Yannik

---

<div class="post-metadata">

**Author:** ![Chrisir](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/chrisir/32/45_2.png) [@Chrisir](https://discourse.processing.org/u/Chrisir)\
**Post date:** [June 25, 2020, 2:08pm UTC](https://discourse.processing.org/t/return-object-in-method-and-use-its-functions/22140/4 "2020-06-25T14:08:22Z")

</div>

> [@Alphaprot](#):
>
> I thought using Object as the method type would be sufficient as I cannot really predict what kind of object is being returned.

I understand now what you mean.

Just stick with Object for the moment.

Upon instantiating each object from the class, you could pass its type as a String (or an integer) to the object: class `Ladder` , class `Door` … as myType

And then after getting the object from the function use `switch(myType) {}` to distinguish between the objects.

* * *

> [@Alphaprot](#):
>
> What do you mean with your second remark?

like this: `ArrayList<ObjectTypeX> list = new ArrayList();`

* * *

> [@Alphaprot](#):
>
> Regarding the two nested for-loops: it should work as expected, since the first loop (extentX) starts at 0 and then all extentY-values from 0 - 30 (actionRadius) are checked (temp1) and then from -30 - 0).

There are 4 quadrants surounding the point

try this:

```auto

PVector pv;

void setup() {
  size(1100, 900);
}

void draw() {
  background(0);

  float actionRadius = 130; 
  float playerxPos = width /2; 
  float playeryPos=height/2;

  noStroke(); 

  for (float extentX=0; extentX<=actionRadius; extentX++) {
    for (float extentY=0; extentY<=actionRadius; extentY++) {

      PVector temp1 = new PVector (playerxPos + extentX, playeryPos + extentY);
      PVector temp2 = new PVector (playerxPos - extentX, playeryPos - extentY);

      fill(random(255), random(255), random(255));
      ellipse(temp1.x, temp1.y, 
        4, 4);

      ellipse(temp2.x, temp2.y, 
        4, 4);
    }
  }
}

```

**Remark**

You can use

```auto
        temp1 = world.getBodies((player.xPos + extentX), (player.yPos + extentY), true);// + + 
        temp2 = world.getBodies((player.xPos - extentX), (player.yPos - extentY), true); // - -
        temp1 = world.getBodies((player.xPos + extentX), (player.yPos - extentY), true); // + - 
        temp2 = world.getBodies((player.xPos - extentX), (player.yPos + extentY), true); // - +
            

```

OR just loop over all objects and check if dist() command gives you something \< actionRadius. See reference

**Remark**

You return only the first item from the ArrayList… so you could check for the nearest or you could return from the function once you found ONE item (the first). Use command return.

Warm regards,

Chrisir

---

<div class="post-metadata">

**Author:** ![Alphaprot](https://avatars.discourse-cdn.com/v4/letter/a/ee7513/32.png) [@Alphaprot](https://discourse.processing.org/u/Alphaprot)\
**Post date:** [June 27, 2020, 2:40pm UTC](https://discourse.processing.org/t/return-object-in-method-and-use-its-functions/22140/5 "2020-06-27T14:40:47Z")

</div>

Hey Chrisir,

could you ellaborate a bit further on your suggestion of using `switch()`?

I’m now circling over everything using “dist” (looks much cleaner 🙂) - thanks for the visual explanation of my error in reasoning; I was quite sure that my method should have worked, but I admit defeat ^^).

I came up with a different approach to use different objects. Simply assign them a name (fortunately, FBody has a method to do so, `setName`) - where `name` represents the variable name storing the object - and then use the method to retrieve the object name needed to access the object’s private methods. _Should_ work…

Warm regards  
Yannik

---

<div class="post-metadata">

**Author:** ![Chrisir](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/chrisir/32/45_2.png) [@Chrisir](https://discourse.processing.org/u/Chrisir)\
**Post date:** [June 28, 2020, 8:23pm UTC](https://discourse.processing.org/t/return-object-in-method-and-use-its-functions/22140/6 "2020-06-28T20:23:49Z")

</div>

> [@Alphaprot](#):
>
> could you ellaborate a bit further on your suggestion of using `switch()` ?

switch() is just another way of

```auto
if(typeObject.equals("Latter") 
{.....} 
 else if(typeObject.equals("bridge")
 {.....}

```

---

<div class="post-metadata">

**Author:** ![Alphaprot](https://avatars.discourse-cdn.com/v4/letter/a/ee7513/32.png) [@Alphaprot](https://discourse.processing.org/u/Alphaprot)\
**Post date:** [June 28, 2020, 8:28pm UTC](https://discourse.processing.org/t/return-object-in-method-and-use-its-functions/22140/7 "2020-06-28T20:28:56Z")

</div>

Thanks, I did a little search on my own and must admit - switch() has certainly some good use cases where it outperforms if-elif-else (or rather else-if; trying not to speak Pythonic in Java ^^), mainly in terms of code readability.

Thank you once more for your help, Chrisir 🙂