Access variable by string name?

Unity Engine
1

Let’s say I have a variable named myVar.

I want to call it using the string “myVar”. Other than setting up hashtables ahead of time, does anyone know a way to do this?

Is there a way to cast/convert “myVar” to myVar?

2 Likes
2

There sure is, using our old friend Reflection. Try the following:

public int myVar = 42;

void OnGUI () {
	if (GUILayout.Button("Output Variable Value")) {
		int newVar = (int)this.GetType().GetField("myVar").GetValue(this);
		Debug.Log("Variable value: " + newVar);
	}
}

If you want to access a variable in another object, simple change this to a reference to that object.

17 Likes
3

Thanks! Do you know the jscript equivalent?

4

Sure, there’s just a few minor syntax differences.

var myVar : int = 42; 

function OnGUI () {
	if (GUILayout.Button("Output Variable Value")) {
		var newVar : int = this.GetType().GetField("myVar").GetValue(this);
		Debug.Log("Variable value: " + newVar);
	}
}
5

Hmm… I’m getting the following error:

NullReferenceException: Object reference not set to an instance of an object
6

Never mind, it’s working now.

Thanks again!

7

Sorry for bumping this old thread but could anyone tell me how tonyd actually corrected the nullreference error ?

1 Like
8

He probably initialized the object to a value (string myVar = “some data”)

… But you should probably make a new thread instead of necroing one from four years ago.

9

Sorry, is it too late now ?

I am trying to call a quaternion by using a bunch of string’s value to recreate the quaternion variable’s name, is that the correct way to do it ?
i.e.: the quaternion is called RunKey1HipsRot,
the string used are Animation+“Key”+IntKey+Bodypart+Type

10

I think he read the docs. :wink:

Reflection in the .NET Framework

11

It’s unfortunately a maze for anyone who doesn’t know what he should look at.
“using System.Reflection” on top of the script did the trick but i still dont know how i should proceed.
doing this just gives me the same null error at the Quaternion newVar line.

string CurrentAnimation = "Run";
int Key = 1;

void Start () {
 string HipsString = CurrentAnimation+"Key"+Key+"HipsRot";
 Quaternion newVar = (Quaternion)this.GetType().GetField("HipsString").GetValue(this);
}
12
  • Is the quaternion you’re trying to reference a field, or is it a property?
  • Is the quaternion you’re trying to reference a field / property of the class that has the Update() function?

Edit:

Also, your current code is searching for a field named “HipsString”, not a field with the name in the HipsString var.

13

It’s a field : Quaternion RunKey1HipsRot = Quaternion.Euler(0f, 0f, 340.2343f);
Ill use it in a Slerp, that’s why it isn’t a vector3.
I dont even do anything besides the Start() yet.

i didn’t really know if

Quaternion newVar = (Quaternion)this.GetType().GetField(CurrentAnimation+"Key"+Key+"HipsRot").GetValue(this);

would work and since i had the same error i thought that it didn’t.
Even with that i have the same error.

That’s the whole script

using UnityEngine;
using System.Collections;
using System.Reflection;

public class IKAnimation : MonoBehaviour {
 public string CurrentAnimation = "Run";
 int Key = 1;
 Quaternion RunKey1HipsRot = Quaternion.Euler(0f, 0f, 340.2343f);
 void Start () {
  Quaternion newVar = (Quaternion)this.GetType().GetField(CurrentAnimation+"Key"+Key+"HipsRot").GetValue(this);
  Debug.Log("Variable value: " + newVar);
 }
}

Still the same error, thanks alot for at least trying to help me :slight_smile: .

14

GetField(String) only finds public fields.

You can use reflection to find private fields, but you’ll need to look at the docs for GetField(String, BindingFlags).

15

Thanks a lot, that worked !

16

Hello SmoothP. I see you know how to solve this. Its the same, but i dont get how i have to do it… :frowning:
i did a post asking almost the same. can you help me please?

http://answers.unity3d.com/questions/1204216/c-variable-name-using-other-variables-values.html#comment-1204626

Thanks a lot!

17

What about if I would like to get a string from an array?
string[ ] myVar={“a”,“b”,“c”};
How do I use this.GetType().GetField thing?

2 Likes
18

I Only Entered Here, to say you: Thanks!!! For Sharing that Method, it worked me perfectly to asign a Sprite Value from a String name. Me ahorraste muchísimo código! saludos desde República Dominicana.

19

this["myVar"] have you tried something like this?

20

@yaroslav It says, that Type “file name (in my case) Inventory.js” does not supports slicing.