Return object (toString)

KTibow

Hi. I'm wondering if I can return an object. Example of working code:

int x; println(x);

In this case, x returns a value. What I want to do is to have a class that can do the same thing. How it would work would look like this:

KTibowInt x; println(x);

Instead of returning "[sketch name][class type][memory place]", I want it to return x.y or something like that.

quark

I your class KTibowInt create a public method called toSTring that returns a String representation of your object e.g.

class KTibowInt {
  // class attributes /fields
  // object methods

  public String toString(){
    // Create and return the String you want to appear when using println()
    return "A string representation of this object";
  }

}

This works with any user defined class.

KTibow

quark, that is not quite what I was thinking of. In the example that I showed, when I type x, it returns an int, not a string.

KTibow

Oh, wait... maybe it would have been more appropriate to use the Integer class. Oh, wait again... x returns itself, right? So, maybe println() does something with it.

quark

When you use println(x) it creates a String representation of the variable x and displays that in the console window. It doesn't matter what the data type of x is, they all work the same way.

If you want to return a value from the class then create a simple getter e.g.

class KTibowInt {
  // class attributes /fields
  int intValue = 0;

  // Constructor
  KTibowInt(int anInt){
    intValue = anint;
  }

  // object methods
  int getIntValue(){
    return intValue;
  }

  public String toString(){
    // This will return a String representation of intValue
    return "" + intValue;
  }

}

Now if you create the object with x = new KTibowint(42); then both these statements will display '42' in the console window.

println(x); // uses toString method
println(x.getIntValue());

KTibow

Well, I guess that's the best I can do in Processing.

KTibow

Of course, in different programming languages, I could do that. But, as far as I know, this form has an answer. Still, somebody else may have a different answer.

quark

Well, I guess that's the best I can do in Processing.

That's the best you can do in Java, it maybe different in Javascript.

If you want something better, then you need to give a more detailed description of what you are trying to do.

koogs

Part of the problem here is the title. 'Return' has a specific meaning in Java and it's not how you're using it.

Add quark says, toString is the way to do exactly what you want. The default for objects is to print the type and address, which is pretty useless but you can override it in your own classes and make it do anything you want, as long as it returns a string. I'd add the @Override annotation to quark's solution.

jeremydouglass

Put another way, you could think of println(x) as "a function that calls x.toString()". Many objects already have a toString, so println already knows what to do with them. If you create a new object, give it a toString method, and then println (the thing that calls toString) will know what to do with it (because it has a toString).

See for example this related Java discussion: https://stackoverflow.com/a/29319217/7207622