how can instantiate this?

[mrcw]

Hi I am getting this error

An object reference is required for the non-static field, method, or property

eyes_and_wheels.servos[wheelLeft].Engaged = true;

I think I need to instantiate wheelLeft, but I've no idea how to. Can anybody help?

mrcw2

[GaryTexmo]

Is that the entire error? It should tell you what it's referring to. Is this a compile error or a run-time error?

Instantiation means creating a new object of a set type. For example, if I'm instantiating a new List of strings, I'd do the following...

List<string> strList;
 
// Instantiate strList
strList = new List<string>();

[Curtis Rutland]

eyes_and_wheels.servos[wheelLeft] = new Whatever();

Replace whatever with whatever the type is, and add parameters as necessary.

Of course, that assumes that class exposes a constructor. It could use a factory pattern. Without knowing what class it is, it's hard to say. But by and large, most have constructors so you should be fine.

[mrcw]

this is a working program. When button 0 is pressed on ifkit1 servo 6 on eyes_and_wheels moves

namespace Robot
{
    class Program
    {
       static AdvancedServo eyes_and_wheels; //Declare an servo object
       static InterfaceKit ifKit1; //Declare an InterfaceKit object
 
       int wheelLeft = 6;
 
       ifKit1.InputChange += new InputChangeEventHandler(ifKit1_InputChange);  //Hook the phidget spcific event handlers
 
       eyes_and_wheels.open(99364); //opens eyes_and_wheels connection
       eyes_and_wheels = null; // clear eyes_and_wheels from memory
       eyes_and_wheels.close(); // close eyes_and_wheels connection
    }
 
     static void ifKit1_InputChange(object sender, InputChangeEventArgs e)
        {
          if (e.Index == 0)
 
                    if (e.Value == true)
                    {
                        ifKit1.outputs[0] = true;
 
                        eyes_and_wheels.servos[6].Engaged = true; //wheelLeft
 
                    }
        }
 

to make it easier for me I changed the name of servo 6 to wheelLeft

namespace Robot
{
    class Program
    {
       static AdvancedServo eyes_and_wheels; //Declare an servo object
       static InterfaceKit ifKit1; //Declare an InterfaceKit object
 
       int wheelLeft = 6;
 
       ifKit1.InputChange += new InputChangeEventHandler(ifKit1_InputChange);  //Hook the phidget spcific event handlers
 
       eyes_and_wheels.open(99364); //opens eyes_and_wheels connection
       eyes_and_wheels = null; // clear eyes_and_wheels from memory
       eyes_and_wheels.close(); // close eyes_and_wheels connection
    }
 
     static void ifKit1_InputChange(object sender, InputChangeEventArgs e)
        {
          if (e.Index == 0)
 
                    if (e.Value == true)
                    {
                        ifKit1.outputs[0] = true;
 
                        eyes_and_wheels.servos[wheelLeft].Engaged = true; //wheelLeft
 
                    }
        }

now I get the error "An object reference is required for the non-static field, method, or property " when I try and run the program. I think it needs to be instantiated, but I'm not sure. Any ideas?

[GaryTexmo]

I don't understand how this code works... your input change method is outside the scope of the class, how does it access those variables? According to what you wrote, ifKit1, eyes_and_wheels, and wheelLeft should not be defined and should give the appropriate errors.

I may be confused and/or not understanding something here... but the way I'm seeing it, the event handler is outside the scope of the Program class.

[Curtis Rutland]

This whole block is your problem:

class Program
    {
       static AdvancedServo eyes_and_wheels; //Declare an servo object
       static InterfaceKit ifKit1; //Declare an InterfaceKit object
 
       int wheelLeft = 6;
 
       ifKit1.InputChange += new InputChangeEventHandler(ifKit1_InputChange);  //Hook the phidget spcific event handlers
 
       eyes_and_wheels.open(99364); //opens eyes_and_wheels connection
       eyes_and_wheels = null; // clear eyes_and_wheels from memory
       eyes_and_wheels.close(); // close eyes_and_wheels connection
    }

This code obviously belongs in a method, but you are writing it inside a class! You can't just have executable code hanging out on its own like that. Classes are for declaring properties, fields, and methods.

I'm assuming this should be your Main method (the one that executes when the program starts).

So try doing something like this:

class Program
{
    private AdvancedServo eyes_and_wheels; //Declare an servo object
    private InterfaceKit ifKit1; //Declare an InterfaceKit object
 
    static void Main(string[] args)
    {
        //this line may not work; instantiate it however you're supposed to
        ifKitl = new InterfaceKit();
 
        int wheelLeft = 6;
 
        ifKit1.InputChange += new InputChangeEventHandler(ifKit1_InputChange);  //Hook the phidget spcific event handlers
 
        eyes_and_wheels.open(99364); //opens eyes_and_wheels connection
        eyes_and_wheels = null; // clear eyes_and_wheels from memory
        eyes_and_wheels.close(); // close eyes_and_wheels connection
    }
}

Note, I added a line to instantiate the object, but it may not work, since I don't know if the constructor requires parameters or not. Also, you'll eventually need to instantiate your AdvancedServo object as well.

[mrcw]

sorry I hate cut and paste it is bad when it copies wrong. The correct code is here, It gives the error when I try and run it

namespace Robot
{
    class Program
    {
       static InterfaceKit ifKit1; //Declare an InterfaceKit object     
       static AdvancedServo eyes_and_wheels; //Declare an servo object
       int wheelLeft = 6;
 
 
      static void Main(string[] args)
        {
            try
            {
                ifKit1 = new InterfaceKit(); //Initialize the InterfaceKit1 object
                eyes_and_wheels = new AdvancedServo(); //Initialize the AdvancedServo object
 
                ifKit1.InputChange += new InputChangeEventHandler(ifKit1_InputChange);  //Hook the phidget spcific event handlers
 
                ifKit1.open(117172); //Open the object for device connections              
                eyes_and_wheels.open(99364);
 
                Console.Read();  //Wait for user input so that we can wait and watch for some event data from the phidget
 
                ifKit1 = null;  //set the object to null to get it out of memory
                ifKit1.close(); //User input was rad so we'll terminate the program, so close the object              
 
                eyes_and_wheels = null; // clear eyes_and_wheels from memory              
                eyes_and_wheels.close(); // close eyes_and_wheels connection
            }
        catch (PhidgetException ex)
            {
                Console.WriteLine(ex.Description);
            }
    }
 
    static void ifKit1_InputChange(object sender, InputChangeEventArgs e)
      {
 
            if (ifKit1.SerialNumber == 117172)
            {
                if (e.Index == 0)
 
                    if (e.Value == true)
                    {                      
                        eyes_and_wheels.servos[wheelLeft].Engaged = true; //wheelLeft
                    }               
            }
        }
} 

[Curtis Rutland]

Lines 24 and 25 should be switched. Likewise for 27 and 28. First you set null, then you call close. You can't call close on null. It needs to be the other way around.

Actually, you don't need to set them to null at all. Your program is ending. The memory they took up will be automatically cleaned up by the garbage collector. And setting them to null doesn't actually free the memory anyway. It just makes those objects available for garbage collection.