C# from void start to void update

Question

1.00/5 (1 vote)

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Hello !

Here my code :

C#

public class Recup_donnees_6bis : MonoBehaviour {

    class Data_struct {

        public String marker_name ;
        public Vector3 [] positions ;

    }

        GameObject [] body ;
        string[][] datas;

        int cpt = 0 ;

    void Awake ()

    {
        Application.targetFrameRate = 25;
    }

    void Start()

    {
        body = new GameObject[55];

        body [0] = GameObject.Find ("RightUpLeg");
        body [1] = GameObject.Find ("LeftUpLed");
        body [5] = GameObject.Find ("Neck");
        body [6] = GameObject.Find ("RightArm");
        body [7] = GameObject.Find ("LeftArm");
        body [8] = GameObject.Find ("Throat");
        body [9] = GameObject.Find ("Spine1");
        body [11] = GameObject.Find ("Spine");
        body [12] = GameObject.Find ("Hips");
        body [13] = GameObject.Find ("Scalp");
        body [14] = GameObject.Find ("HeadTop_End");
        body [15] = GameObject.Find ("R_Temple");
        body [16] = GameObject.Find ("L_Temple");
        body [17] = GameObject.Find ("RightForeArm");
        body [21] = GameObject.Find ("RightHand");
        body [23] = GameObject.Find ("RightHandIndex1");
        body [24] = GameObject.Find ("RightHandThumb2");
        body [25] = GameObject.Find ("RightHandPinky2");
        body [26] = GameObject.Find ("LeftForeArm");
        body [30] = GameObject.Find ("LeftHand");
        body [32] = GameObject.Find ("LeftHandIndex1");
        body [33] = GameObject.Find ("LeftHandThumb2");
        body [34] = GameObject.Find ("LeftHandPinky2");
        body [35] = GameObject.Find ("RightLed");
        body [38] = GameObject.Find ("RightFoot");
        body [41] = GameObject.Find ("RightFootToeBase_End");
        body [42] = GameObject.Find ("RightToeBase");
        body [45] = GameObject.Find ("LeftLed");
        body [48] = GameObject.Find ("LeftFoot");
        body [51] = GameObject.Find ("LeftFootToeBase_End");
        body [53] = GameObject.Find ("LeftToeBase");

        StreamReader reader = new StreamReader ("Suj01_PI_DP_C00_1.txt");

        using (reader) {

            string line = " ";
            int lineNumber = 10;

                for (int i = 0; i < lineNumber; i++)
                {
                    line = reader.ReadLine();
                    if (line == null) return;
                }

            string line_10;
            line_10 = line;
            string[] names = line_10.Split (new String[] {",",",,,"},StringSplitOptions.RemoveEmptyEntries);

            Data_struct [] nv_data ;
            nv_data = new Data_struct[names.Length] ;

                for (int i =0 ; i< names.Length; ++i )
                {
                    nv_data[i] = new Data_struct () ;
                    nv_data[i].marker_name = names[i] ;
                }

            line = reader.ReadLine();
            string line_11;
            line_11 = line;
            string[] axes = line_11.Split(new String[] {"Field #",","},StringSplitOptions.RemoveEmptyEntries);


            datas = new string[4000][];

            int counter = 0;
            while (line != null) {
                counter++;
                line = reader.ReadLine();

                if (line == "ANALOG")
                break ;

                if ((counter %3) != 1)
                    continue;

                string lines_datas;
                lines_datas = line;
                datas[cpt] = lines_datas.Split(new string[] {","},StringSplitOptions.RemoveEmptyEntries);

                line = reader.ReadLine();


                cpt ++ ;


            }

                for (int i = 0 ; i < cpt ; ++i )
                {
                    for (int j = 1 ; j < names.Length+1 ; j++ )
                {
                    nv_data[j-1].positions = new Vector3[cpt];

                nv_data[j-1].positions[i].x = float.Parse(datas[i][j*3-2]);
                nv_data[j-1].positions[i].y = float.Parse(datas[i][j*3-1]);
                nv_data[j-1].positions[i].z = float.Parse(datas[i][j*3]);
                }

            }

        }

    }

 void update ()

{

        // To associate names_markers to avatar_joints :

        for (int k = 0 ; k < body.Length ; ++k)

            body[k].transform.position = nv_data[k].positions[k];



    }

}

My problem : at the last line "nv_data" doesn't exist at the current context.
I think I know for why but I don't know how I can fix this problem.
I'm forced to integrate this last line in "void update ()" because it varies each frame.

Could you help me, please ?

Posted 5-Mar-15 21:13pm

Coralie B

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OriginalGriff · Accepted Answer · 2015-03-05T21:37:00

Solution 1

nv_data doesn't exist because it is a variable local to the start method, and you are trying to access it in the update method.

That's like putting your mobile phone in the glove-box of your car, and expecting to find it when you open the glove-box in my car!
Local variables are just that: local to the method they are declare within, and are destroyed on exit from the method. The data that it referenced still exists (probably) however, since it is on the heap.

You may be able to solve this by moving the declaration of nv_data outside the method, to make it a class level variable:

C#

private Data_struct [] nv_data;
void start()
   {

But it sounds like you need to go back a few steps and re-read your course notes from the beginning - you seem to be trying to run before you can walk! :laugh:

"t's exactly this point that I think I'm lost.
When I use a constructor to create an object, I'm creating an instance. But concretely, what is it ? "

The problem is that this is pretty much fundamental: everything in C# is object based, which means that with very few exceptions everythign is instance based.

What is an instance? Ok...try this.

What colour is a car?

Answer: It doesn't have one. A car doesn't have a colour.
"This car" has a colour. "That car" has a colour. Your car; my car; his car; these all have a colour. But "A car" doesn't have a colour because not all cars are the same: some are red, some blue, some silver, ... You need to specify exactly which car you are talking about in order to refer to it Colour - which is just one of it's properties - the same applies to all the other properties such as engine size, number of doors, fuel consumption, fuel type, etc.

And that's important, because "car" is an abstract concept, and "this car", "that car", "your car", "my car", "his car" are examples of that abstract concept. You can drive a car, but you need a specific car in order to get down to the shops!

In computer terms, "car" is a class, and "this car" is an instance of the "car" class:

C#

public class Car
   {
   public Color Color;
   public int EngineSize;
   public Car(Color color, int engineSize)
      {
      Color = color;
      EngineSize = engineSize;
      }
   }
...
   Car thisCar = new Car(Color.Red, 1600);
   Car joesCar = new Car(Color.Blue, 5500);

Seriously, my friend: you need to get a book and follow it from beginning to end. You need to know this stuff, and loads of other bits - which you can't pick up on an ad-hoc basis. If you don't, you will just get more and more confused.

Posted 5-Mar-15 21:37pm

OriginalGriff

Updated 6-Mar-15 4:36am

v2

Comments

Coralie B 6-Mar-15 4:35am

Thank you for the solution and your explanation.
But this doesn't run ...

I had never had any course of the programming. I am in training, and it's not really my role to use the programming but I need it to continue the project.

To be honest I really struggle to understang the programming...

OriginalGriff 6-Mar-15 4:52am

Seriously, to do anything practical with any .NET language, there is a huge amount you need to learn. Otherwise, you end up creating something that is badly designed, poorly written, bug ridden, and unmaintainable.

And your code is showing a lot of the signs of "I don't understand what is going on here" development.
I'd strongly suggest you get a course, or a book and work though it - that way you get all the elements introduced in a logical progression. Trying to learn just by "doing it" is a bad idea as you have no idea if what you do is the best way or if there is a simpler, cleaner solution. And there very often is! Without "formal" teaching in the subject, you don't even know what you are missing, let alone why it matters!

In this case "this doesn't run" tells me absolutely nothing about your problem: it's like phoning the garage saying "my car broke" and putting the phone down. The garage is not going to arrive where you are with the right bits to fix it any time soon, as they don;t know who you are, where you are, what car it is, what broke, what parts you might need, what help you want, ... see what I mean?

Coralie B 6-Mar-15 5:17am

When I have said "this doesn't run" means that your solution doesn't a solution for my problem. It's ever the same : nv_data doesn't exist at the current context.

I see what you mean. If I ask specific questions, you want to help me ?

If it's the case : my question would be :
How can I make an animation with a variable which has been declared before, out of my function ("void update ()" in my case) ?

OriginalGriff 6-Mar-15 5:50am

Asking "specific questions" isn;t a solution: *you don't know what questions to ask* - and that means you don't understand the answers.

Look at my suggestion: "You may be able to solve this by moving the declaration of nv_data outside the method, to make it a class level variable:"
How much of that do you understand?
What did you do to try it?

Coralie B 6-Mar-15 5:57am

I put "private Data_struct [] nv_data;" in class Data_struct {}
I have understood that I have to declare this variable not like a local variable. Otherwise, this variable would exist only into the function where it is declared.

OriginalGriff 6-Mar-15 6:03am

And that was exactly what your error message was telling you.
Now, did you remove the definition from the start method, or did you leave that in there as well?
Because if you left it in there, the local variable version will be used in preference within start and the class level version ignored.

Coralie B 6-Mar-15 7:56am

Thank you;I think I have found a solution thanks to you (of course) !
Actually, I put "private Data_struct [] nv_data ;" after class Data_struct {} so out any function. And I had already removed that in "void start {}".
I didn't have any error now !

But, is that the data entered into nv_Data from " void start {}" are still valid once outside of this function ? Or Nv_data is empty?

I think it's empty. So is there a solution to avoid the destroying, when it's out of the function where it has been completed, of items and datas in nv_Data ?

Thank you again

OriginalGriff 6-Mar-15 8:19am

Oh boy...This is going to be confusing, I can tell...So I'll try to explain from the beginning - just tell me where I start losing you... :laugh:
Hopefully, I won't be covering too much that you already know and sound patronising - if I do, it's because I have no idea what you know at this stage.

Variables inside a class (but outside a method) are called "class level variables" and they exist within the confines of an instance of the class.
So:
public class MyClass()
{
private string myString;
public void SetString(string s) { myString = s; }
public string GetString() { return myString; }
}
When you call SetString it sets the class level variable value, and that remains available once the method has ended - so GetString can return the right value when you call it later. Provided you use the same instance.

Do you know what an instance is?

Coralie B 6-Mar-15 8:39am

It's exactly this point that I think I'm lost.
When I use a constructor to create an object, I'm creating an instance. But concretely, what is it ?
My instance in my code is
StreamReader reader = new StreamReader ("Suj01_PI_DP_C00_1.txt");
using (reader) {
...
}
?

Thank you again.
I understand what you mean while I'm not english and I begin to understand the structure of c#.
I continue to read websites about this programming while you help me. Some things appear for me more understood than before. So thank you

OriginalGriff 6-Mar-15 10:37am

Answer updated

johannesnestler 6-Mar-15 7:13am

I think Griff is very patient and helpfull to you, but If I consider the time it costs you reading and posting question you could have read chapter one on C# programming of any tutorial too. "how to declare variables and variable-scopes..." Sorry but this QA won't help you mutch, if you are not willing to learn. Even assuming that you could go for such a complicated "Task" like programming without any knowledge is "strange" in my opinion. Would you consider doing a heart-surgery with zero knowledge about medicine?

TheRealSteveJudge 8-Mar-15 5:26am

Your patience in helping f*ckwits is unbelievable! 5 stars.

Coralie B 9-Mar-15 4:28am

So :
My class is : class Data_struct {
My instance is : private Data_struct [] nv_data ;

That's right ?
If it's the case, I have to write :

class Data_struct {

private string nv_data;
public void SetString(string nv_data) { nv_data = nv_data; }
public string GetString() { return nv_data; }
}

Can I call with the same name ?

And I have to call it here ?

void update ()

{

// To associate names_markers to avatar_joints :

GetString(nv_data);

for (int k = 0 ; k < body.Length ; ++k)

body[k].transform.position = nv_data[k].positions[k];

}

Thank you very much

OriginalGriff 9-Mar-15 6:10am

No! Sorry, but

private Data_struct [] nv_data ;

is not an instance - it's an array of instances, in the same way that a car park is on an instance of a car: it's an array of instances of cars. You can't drive a car park! :laugh:

And your code is wrong as well - it declares nv_data as a variable capable of holding an array of Data_struct objects, but it doesn't actual create the arry, or any instances to put into it.

And it's a very, very poor idea to use the same name for two different objects in the same class - it's far far too easy to get confused as to which you mean.

You haven't quite grasped all this yet - the second example code won't even compile as you pass a parameter to a method that doesn't have any parameters, and don't use the result it returns.

Please, stop guessing - it really isn't a good strategy here - and think about it.
AND GET A BOOK! :laugh:
Asking individual questions isn't going to help much if you don't understand the fundamentals they rely on - and you clearly need to get the fundamentals straight here, there are no short cuts round that.

Coralie B 9-Mar-15 6:17am

Ok, thanks for your all help.

I never thought that this could be bad to ask for help as I did, so thank you again, and my apologies.

OriginalGriff 9-Mar-15 8:31am

You're welcome!
(And it's not *bad* to ask for help - but you really do need to know the basics of swimming before you start to dive in the deep end of the pool... ;)

Coralie B 9-Mar-15 8:50am

In generally, we learn swimming with someone who knows how we can do it, no ? During the beginning of the apprenticeship.

And in my case I have to work alone about a purpose which unknown to me.
So, I'm trying to do it and when I was blocked, I asked for help. I thought that was how the forums worked.

Brief, thank you again

OriginalGriff 9-Mar-15 9:07am

There are two ways to learn to swim:
1) With a teacher who can guide you through in the "shallow end" and make sure you don't try to breath underwater.
2) By jumping in the deep end and hoping it'll all work out fine, and yelling for help when it doesn't work.

The first is a course, or a book; the second is what you are trying to do. :laugh:

Coralie B 10-Mar-15 8:41am

I'm trying to find the problem, I have added some lines :

void Update () {

for (int i = 0; i < cpt; ++i) {
for (int k = 0; k < body.Length; ++k)
{
if(body == null)
Debug.Log("body is null!");

if(body[k] == null)
Debug.Log("body["+k+"] is null!");

if(body[k].transform == null)
Debug.Log("body["+k+"].transform is null!");

if(nv_data == null)
Debug.Log("nv_data is null!");

if(nv_data[k] == null)
Debug.Log("nv_data["+k+"] is null!");

body[k].transform.position = nv_data[k].positions[i];
Debug.Log(body[1].transform.position);

}
}
}

The errors are :

"body [1] is null !" so my problem is about body[k]
"nv_data is null !" so my problem is about nv_data (it appears when I stop the animation)
"Object reference not set to an instance of an Object" for the line : if(body[k].transform == null)

OriginalGriff 10-Mar-15 8:51am

No, it isn't.
If body was null here:
if(body == null)
Debug.Log("body is null!");
Then this line:
for (int k = 0; k < body.Length; ++k)
would have thrown an exception as trying to get at any property of a null value is a "null reference" exception

It's good you are trying, but what happens if you try to step though the code in the debugger?

Coralie B 10-Mar-15 9:58am

If I use the debugger at the breakpoint "body[k].transform.position = nv_data[k].positions[i];"

Some items of body[] doesn't exist !
For examples : body[0] exists and from body [1] to body [4] don't exist ! etc ...
Why ? I took the name of GameObject from directly to unity...

And for the string nv_data ... It's disturbing ...
All of value positions are 0 !
But when I used debug.log to see my value positions into the string nv_data (below the lines which allow me to have nv_data.positions) they have so 0 ... But with debug.log we can see positions values of nv_data...

But, for these variables, for their initialization , I did it :
private static Data_struct [] nv_data;
private static GameObject [] body;
"static" allows me to have them in all instances...
So in the debugger, they appear in "static members"
But if I remove "static" nothing changes. There are here again.
So "static" doesn't have any utility here.
I remove it so ?

OriginalGriff 10-Mar-15 11:01am

Seriously, stop playing with this and get a book!
I *know* it's dull, and I *know* it's not what you want to do - but it will save you massive amounts of time in the future.

I can't tell you why body doesn't have what you want - because I can't run your code. You can try looking at what happens to body in the beginning with the debugger, and I think I know what'll happen - but really you need to learn what you are doing before you try and go any further.

Coralie B · Accepted Answer · 2015-03-12T05:15:00

C#

using System.Collections.Generic;
using System.Text;
using System.IO;
using System.Collections;
using System.Text.RegularExpressions;
using UnityEngine;
using System;


public class Recup_donnees_7 : MonoBehaviour {

    private bool paused; 

    private class Data_struct {

        public String marker_name ; 
        public Vector3 [] positions ; 

    }

    private Data_struct [] nv_data ;
    public GameObject [] body  = new GameObject[55]; 

    string[][] datas; 

    int cpt = 0 ; 
    int i;
    int j;
    int k;
    int frame ;


    // When the script instance is being loaded

    void Awake ()

    {
        Application.targetFrameRate = 25; 
    }


    // Use this for initialization

    void Start() 

    {
        paused = true;
        frame = 0;

        StreamReader reader = new StreamReader ("Suj01_PI_DP_C00_1.txt"); 

        using (reader) {

            string line = " "; 
            int lineNumber = 10; 

            for (int n = 0; n < lineNumber; n++)
            {
                line = reader.ReadLine(); 
                if (line == null) return; 
            }

            string line_10;
            line_10 = line; 
            string[] names = line_10.Split (new String[] {",",",,,"},StringSplitOptions.RemoveEmptyEntries); 

            nv_data = new Data_struct[names.Length] ;

            for (int x =0 ; x< names.Length; ++x )
            {
                nv_data[x] = new Data_struct () ; 
                nv_data[x].marker_name = names[x] ; 
            }

            line = reader.ReadLine(); 
            string line_11;
            line_11 = line;
            string[] axes = line_11.Split(new String[] {"Field #",","},StringSplitOptions.RemoveEmptyEntries); 

            datas = new string[4000][]; 

            int counter = 0;
            while (line != null) { 
                counter++;
                line = reader.ReadLine(); 

                if (line == "ANALOG") 
                    break ;

                if ((counter %3) != 1) 
                    continue;

                string lines_datas; 
                lines_datas = line;
                datas[cpt] = lines_datas.Split(new string[] {","},StringSplitOptions.RemoveEmptyEntries); 
                line = reader.ReadLine(); 

                cpt ++ ;

            }

            for (j = 1 ; j < names.Length+1 ; j++ )

                nv_data[j-1].positions = new Vector3[cpt]; 

            for (i = 0 ; i < cpt ; ++i ) 
            {
                for (j = 1 ; j < names.Length+1 ; j++ ) 
                {
                    nv_data[j-1].positions[i].x = float.Parse(datas[i][j*3-2]);
                    nv_data[j-1].positions[i].z = -float.Parse(datas[i][j*3-1]);
                    nv_data[j-1].positions[i].y = float.Parse(datas[i][j*3]);
                }
            }
        }
    }

    // Update is called once per frame
    void Update () {

        if (frame < nv_data[0].positions.Length) 

            for (k = 0; k < body.Length; ++k)

        {
            if(body[k] != null) 

            {
                body[k].transform.localPosition = nv_data[k].positions[frame]/1000;
            }

            else
                continue;

        }

        frame++; 

        paused = true; 

    }

}