Struct in JavaScript

Question

Hello,

Is there a way to make a structure in JavaScript? I mean not class but structure as Vector3 for example. For creating big fast arrays. Something like this:

struct SomeStruct{ var i : int; var f : float; }

var arr = new SomeStruct[1000];
arr[500].a = 3;

In a case of class I need to initialize every member of the array...

Answer 1

Best Answer

Answer by Senhor de todo o Mal · Jan 24, 2011 at 10:37 AM

A struct is basically a value type so you can try something like this:

 class SomeStruct extends System.ValueType{
   var i : int;
   var f : float;
 
   public function SomeStruct(i:int,f:float){
      this.i = i;
      this.f = f;
   }
 }

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Fattie · Dec 23, 2011 at 11:14 AM 0

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One of the best answers ever posted on this site! Thanks.

Just for the record, it appears you CANNOT (as of 2011) make a default constructor.

 public function SomeStruct(i:int,f:float)
 // this is the constructor, if you need one
     {
     this.i = i;
     this.f = f;
     }
 function SomeStruct()
 // would be a default constructor, BUT YOU CANNOT DO THIS!  :)
     {
     this.i = 99;
     this.f = 3.14159265;
     }

If you try the latter, you get the error: "Value types cannot declare parameter-less constructors". So in answer to Santa's question below you will always simply get the normal default values for the members. (Of course, you could make some sort of initialiser which you could run as needed.) Further in answer to Santa's question, yes you can make lovely javascript arrays of these "structs" as in any normal language.

 private var stuff:SomeStruct[];

and then

 stuff = new SomeStruct[42000];

end then

 stuff[28033].i = 6;
 height = stuff[197].f * 99.123;

All of this, thanks to @Senhor !! Merry Xmas.

Answer 2

Answer by Mike 3 · Jul 22, 2010 at 02:57 PM

Turns out it is possible (Thanks to Senhor de todo o Mal for pointing that out)

class YourStruct extends System.ValueType
{
    //code
}

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Santa · Jul 22, 2010 at 04:54 PM 0

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Strange, but if I've placed the structure separately into "Standard Assets" folder. And compiler gives an error "The name 'SomeStruct' does not detonate a valid type'. As if it not present at all. How to compile it earlier other way? Or some way to include or import it?

Mike 3 · Jul 22, 2010 at 05:34 PM 2

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That's exactly how it should work, assuming your javascript file isn't in another earlier compile folder. You should however make your struct public, but it shouldn't give you that error for that

Santa · Jul 22, 2010 at 05:48 PM 0

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With "public" it works :) Thank you!

Answer 3

Answer by Ippokratis · Feb 02, 2011 at 11:28 AM

Building on the example given by Senhor de todo o Mal. Save the following script in your Standard Assets folder:

class SomeStruct extends System.ValueType{

//fields
var i : int;
var f : float;

//Constructor 
public function SomeStruct(i:int,f:float){
 this.i = i;
 this.f = f;
}
//Method
public function PowerOfI(a:int)
{

 for (var index:int = 1; index&lt;a; ++index)
 {
     this.i = this.i * this.i;
 }

}

Now create a new js script as follows:

function Start () {
    //Make a new SomeStruct with uninitialized fields
    var myStruct:SomeStruct = new SomeStruct();
    //Set field i
    myStruct.i =5;
    //Test it
    Debug.Log(myStruct.i);
    //Make a new SomeStruct with initialized fields
    var myStruct2:SomeStruct = new SomeStruct(5, 2.3);
    //Test it
    Debug.Log(myStruct2.f);
    //Use a struct method
    myStruct2.PowerOfI(2);
    //Test it
    Debug.Log(myStruct2.i);
}

So yes, you can create structures in Unity JavaScript.

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Santa · Feb 02, 2011 at 08:39 PM 0

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But what if I create huge array without initialization of each item with "new"? Will I be able to access their members ".i" or ".f"? As far as I understand it's still pointers. Or not? PS: Can't check it out quickly by myself because I moved all scripts in C# long ago.

Senhor de todo o Mal · Feb 03, 2011 at 10:57 AM 0

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Its basically an array of value types so each item will have the default value of that value type. For example, int will be 0, float will be 0.0f and boolean will be false.

Q_B · Feb 17, 2011 at 05:37 PM 0

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Great info you guys got here, thx! Unfortunately, when trying to declare an array of structs created like this, they won't show up on the editor. For instance, if I put a " var w : float[] ", it shows on the editor allright. But if I put a " var w : mystruct[] ", it does not reports errors, but it doesn't shows on the editor :( Any idea how to solve this, if it's even possible?

Ippokratis · Feb 20, 2011 at 10:49 AM 0

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Senhor de todo o Mal did it single handed. I was just too excited it worked and I wanted to post it ! No code formating was available in comments so I posted it as answer. So to be clear: All kudos go to Senhor. Regarding your question : Try to set the Inspector in Debug mode (from the drop-down menu on the upper right corner).

Answer 4

Answer by kblood · Apr 26, 2013 at 07:25 PM

This has annoyed me for days. Doing it the way Senhor de todo o Mal did it does not make the struct show up in the editor. Then I found this in another answer:

http://docs.unity3d.com/Documentation/ScriptReference/Serializable.html

 class Test extends System.Object {
     var p = 5;
     var c = Color.white;
 }
 var test = Test ();

And now it shows up in the editor as well. I hope it saves others some time.

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Fattie · Apr 26, 2013 at 07:32 PM 1

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be super-careful with this gotchya !

http://answers.unity3d.com/questions/261419/you-own-structs-passed-by-reference.html

what you are doing there IS NOT a struct, it's just a class. Totally different eh!! Take care!

Struct in JavaScript

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be super-careful with this gotchya !

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