Something obvious that i'm not able to see

I have a problem... basically, i cant modify the alpha of a text... and i Don't know the reason... i've tried a lot of different ways of writting the same code to do exactly the same, but just i can't... the only thing i want to do is to make the text invisible in a fixed time. but i have an error that dont let me build the code.

Code (CSharp):

1. using UnityEngine;
2. using UnityEngine.UI;
3. using System.Collections;
4.  
5. public class class_PointsMade : MonoBehaviour {
6.  
7.     public GameObject objetoPuntos;
8.     public Text textPoints;
9.  
10.     float alpha = 0f;
11.  
12.     float tiempo = 0f;
13.  
14.     void Update()
15.     {
16.         tiempo+= Time.deltaTime;
17.         this.transform.Translate(1f * Time.deltaTime, 1f * Time.deltaTime, 0f, Space.World);
18.  
19.         if (tiempo >= 2f)
20.             Destroy(this.gameObject);
21.  
22.         alpha = Mathf.Lerp(0f, 1f, Time.deltaTime);
23.  
24.         textPoints.color.a = alpha;
25.  
26.  
27.     }
28. }

 

and here the error Assets/Scripts/class_PointsMade.cs(24,28): error CS1612: Cannot modify a value type return value of `UnityEngine.UI.Graphic.color'. Consider storing the value in a temporary variable. It must be something really simple... but i just cant see what it is...

 

Try:

Code (CSharp):

1. Color textcolor = textPoints.color;
2. textcolor.a = alpha;
3. textPoints.color = textcolor;

The reason for this is that color is probably generated by some logic and doesnt actually have a backing variable. If you do this it will use the new color fine.

 

You need to get the textPoints.Color, change the alpha component and then set it back ie:

Code (csharp):

1. Color col = textPoints.color;
2. col.a = alpha;
3. textPoints.color = col;

 

If you want to not see it, you could deactivate it, for this I think I have the solution :

Code (CSharp):

1. Color color = textPoints.color;
2. color.a = ....;
3. textPoints.color = color;

 

He wants it to slowly fade

In C# there are some cases, where you can't just simply set one of the variables, examples like this is transform.postion/rotation, rigidbody.velocity etc. You need to set the whole thing at once or use a temporarly variable

 

I already told him to do so. Look at my script

 

maybe this should work

http://docs.unity3d.com/ScriptReference/Color.Index_operator.html

 

Ye, I tried that. see

Code (CSharp):

1. using UnityEngine;
2. using UnityEngine.UI;
3. using System.Collections;
4.  
5. public class class_PointsMade : MonoBehaviour {
6.  
7.     public GameObject objetoPuntos;
8.     public Text textPoints;
9.  
10.     Color color = textPoints.Color;
11.  
12.     float alpha = 0f;
13.  
14.     float tiempo = 0f;
15.  
16.     void Update()
17.     {
18.         tiempo+= Time.deltaTime;
19.         this.transform.Translate(1f * Time.deltaTime, 1f * Time.deltaTime, 0f, Space.World);
20.  
21.         if (tiempo >= 2f)
22.             Destroy(this.gameObject);
23.  
24.         alpha = Mathf.Lerp(0f, 1f, Time.deltaTime);
25.  
26.         //textPoints.color.a = alpha;
27.  
28.  
29.     }
30. }

and this error: Assets/Scripts/class_PointsMade.cs(10,23): error CS0236: A field initializer cannot reference the nonstatic field, method, or property `class_PointsMade.textPoints'

for some reason, i cant access to textPoints.color to make the reference to color

 

You can't in C#, it is allowed in Java to directly set the components but not in C#, you have to get a copy of the values, then set the component you want then write it back as is shown multiple times above.

 

I have some problems making that... I have seen other Scripts ive made, and they work

text.color = Color.Lerp (text.color, Color.clear, Time.deltaTime * 3);

text was the text variable of type Text... I saw this code made on C# and it works, the text dissapear.

but in my class_Pointsmade that i shown before, dont allow me to write exactly the same...

This class is inside a prefab like this: https://gyazo.com/79a0c6cd604b533f7f466958f4176a4f

that gameobjects are instantiated CORRECTLY on screen with a game controller script... and i had no problem changing the text and the color in this "game controller"... so... what i'm missing

 

In case you're talking about JavaScript (UnityScript), that's not the same as Java.

What you're missing is the difference between value types (struct in this case) and reference types, and what exactly happens when you "copy" a variable of them or to be more precise in this case, what happens when structs are used in conjuction with properties. (text.color is a property).

 

Since we are in a Unity forum and talking about scripting I was assuming people would understand Java meant Javascript

 

Code (CSharp):

1. using UnityEngine;
2. using UnityEngine.UI;
3. using System.Collections;
4.  
5. public class class_PointsMade : MonoBehaviour {
6.  
7.     public GameObject objetoPuntos;
8.     public Text textPoints;
9.  
10.     Color color = textPoints.Color;
11.  
12.     float alpha = 0f;
13.  
14.     float tiempo = 0f;
15.  
16.     void Update()
17.     {
18.         tiempo+= Time.deltaTime;
19.         this.transform.Translate(1f * Time.deltaTime, 1f * Time.deltaTime, 0f, Space.World);
20.  
21.         if (tiempo >= 2f)
22.             Destroy(this.gameObject);
23.  
24.         alpha = Mathf.Lerp(0f, 1f, Time.deltaTime);
25.  
26.         color.a = alpha;
27.        textPoints.color = color;
28.  
29.  
30.     }
31. }

 

I can't write Color color = textPoints.color; it gives me an error that I posted before: "A field initializer cannot reference the nonstatic field, method, or property `class_PointsMade.textPoints

So... What I need to do? I have a Gamecontroller empty on the hierarchy that instatiate this points prefabs... there I could modify thetextPoints.color without any problem...

Code (CSharp):

1. GameObject newPointsMade = Instantiate (objetoPuntos) as GameObject;
2.         class_PointsMade pointsObject = newPointsMade.GetComponent <class_PointsMade>();
3.         pointsObject.textPoints.text = textPoints;
4.         pointsObject.textPoints.color = colorPoints;
5.         newPointsMade.transform.SetParent(myPanel);
6.         newPointsMade.transform.localScale = new Vector3 (1f, 1f, 1f);
7.         newPointsMade.transform.position = positionPoints;

"

 

You cant do that as a field initializer

This means you cant initialize it in the class definition like that That is reserved for using new/static/value types. You need do it in a constructor or because it is a MonoBehaviour you need to do it in Awake/Sleep. Like this

Code (CSharp):

1.  
2. void Start()
3. {
4. color = texPoints.color;
5. }

 

I solved it adding thet Start() function. I still don't know the reason why this worked and the other not.

Code (CSharp):

1. using UnityEngine;
2. using UnityEngine.UI;
3. using System.Collections;
4.  
5. public class class_PointsMade : MonoBehaviour {
6.  
7.     public GameObject objetoPuntos;
8.     public Text textPoints;
9.  
10.     Color color;
11.  
12.     float alpha;
13.  
14.     float tiempo = 0f;
15.  
16.     void Start ()
17.     {
18.         alpha = 1f;
19.         color = textPoints.color;
20.     }
21.  
22.     void Update()
23.     {
24.         tiempo+= Time.deltaTime;
25.         this.transform.Translate(1f * Time.deltaTime, 1f * Time.deltaTime, 0f, Space.World);
26.  
27.         if (tiempo >= 2f)
28.             Destroy(this.gameObject);
29.  
30.         alpha = Mathf.Lerp (alpha, 0f, Time.deltaTime * 1f);
31.  
32.         color.a = alpha;
33.  
34.         textPoints.color = color;
35.  
36.  
37.         //textPoints.color.a = alpha;
38.  
39.  
40.     }
41. }

Making the initialization on Start() works fine...

in alpha =Mathf.Lerp(0f, 1f, Time.deltaTime);
it makes an interpolation between 0f and 1f, based on t (Time.deltaTime in this case). But it makes the same interpolation every frame... so if you have alpha = Mathf.Lerp(0f, 1f, 0.5f); the result is always going to be alpha= 0.5f and it never reachs 1f. So i had to make this alpha = Mathf.Lerp (alpha, 0f, Time.deltaTime); so it always start on the value on alpha... The problem with this is it makes not a linear interpolation. So if some1 knows how to make a REAL linear interpolation, please reply this.

Thanks for your Help people... You are the Best

Edit: Thnaks Korno for your help and the explanation... I did the start() (just because I was trying a lot of different things) and I didn't know Why it works

 

You have to increase the value for t, while start and end stays the same. t=0 returns the start value, t= 1 the target value. So the simplest way to make this work is having a variable starting with 0 and add Time.deltaTime to it in every frame.