Create Events in derived class of CNi4882Device

Using VB and CW GPIB ActiveX control, we are able to do this:
CWGPIB1.NotifyMask = cwGPIBRQS
CWGPIB1.Notify
Private Sub CWGPIB1_OnGPIBNotify(ByVal mask As Integer)
In VC++, i have created a derived class from CNi4882Device. How do I add event capabilities to it and get the same callback mechanism as in the VB example?

You will use the InstallEventHandler function. You can use it to install an event for any event mask that you want. Then you can just override the OnEvent virtual member of the class and handle the event however you like. You can also install an external (outside the class) function to handle the event, but since you are deriving from CNi4882Device, it would make more sense to override the virtual member OnEvent. See the online help for CNi4882::InstallEventHandler and CNi4882:nEvent for more help.
Best Regards,
Chris Matthews
National Instruments

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Dear all,
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could you please tell me in detail. why so. or any reference for it. i love to read.
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Hello everybody,
I create a GUi application in java swing. Now i want to navigate between the screen but the timing between the screen is very slow bcoz i imported the class from package to another package. Now i want to extends one package to another package to reduce the navigation time but it saying error bcoz i cant able to call my derived class to base class. if anyone know the answer for this please answer this immediately.
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by
(kamal)

Sorry, I've got major difficulties understanding your query:
I create a GUi application in java
ication in java swing. ok
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bcoz i imported the class from package to
another package.how did you come to the conclusion that that is the reason for the slowness? Did you do any profiling or is this just guess-work?

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Does the Java Language Specification explicitly allow setting of fields of a derived class from within the base class' constructor via reflection? The following test case runs green, but I would really like to know if this Java code is compatible among different VM implementations.
Many thanks for your feedback!
Norman
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Hi all,
I have
class Base {
int a;
class Derived{
int b;
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Derived D = new Derived();
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Thanx

Manthana wrote:
Hi, u said
the value of X becomes the reference to the instance of Derived that you created when you called "new Derived()".
So now i can access attributes of derived class from the reference X right X.b
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Why?Please spell out words like "you". It makes things easier to read. :)
With Derived extending Base, you could say:
X = D;
X.a = 5;Because the compiler and runtime see X as a reference to a Base object, you can only access variables/methods defined in Base. Since X is declared as being a reference to Base, you always know that 'a' is defined. 'b' wouldn't be defined for X if you said:
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When is a def assigned to his constant value in a derived class ?

Hi ,
I encountered some strange thing in my app when using a def in a derived class from abstract base class. (dived by zero exception)
I point it out here using a small code snippet which reflects the problem in my app:
public abstract class Base{
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I changed the code to:
public mixin class Base {
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public class BaseDerived extends Base {
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# BaseDerived (Before computation)
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Constant: 0 --> BAD
Temp: 0.0
# BaseDerived (After computation)
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Base Init
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BaseDerived Init
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BaseDerived PostInit
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I just need to read something on what "mixin" differs from abstract.
cheers
Guy

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I think that you can´t assign an object of the base class
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Suppose I have a base class with a method, and a derived class which overloads the method:
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You can change the class
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Hi pls go through the below code, can any one give me solution how to access the Derived class method in this Point.
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Why iam casting to base class is , since only in the run time we are geting the Derived class name.
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class MyDerived extends MyBase
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System.out.println("Derived class Mthode");
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The problem is, can not have subclass reference bcoz
iam geting the subclass name only in the runtime and
one more thing is cant touch my base and subclass to
do changes as u said Your design is then definately very bad.
, is there any other way to do
it.Yes, you can use reflection to invoke the method.
Kaj

Force Derived Class to Implement Static Method C#

So the situation is like, I have few classes, all of which have a standard CRUD methods but static. I want to create a base class which will be inherited so that it can force to implement this CRUD methods. But the problem is, the CRUD methods are static. So
I'm unable to create virtual methods with static (for obvious reasons). Is there anyway I can implement this without compromising on static.
Also, the signature of these CRUD methods are similar.
E.g. ClassA will have CRUD methods with these type of Signatures
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So I want to create a base class with exact similar signature, so that inherited derived methods will implement their own version.
For E.g. BaseClass will have CRUD methods like
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public virtual static BaseClassGet(int ID)
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public virtual static bool Update(int ID)
public virtual static bool Delete(int ID)
But the problem is I can't use virtual and static due to it's ovbious logic which will fail and have no meaning.
So is there any way out?
Also, I have few common variables (constants) which I want to declare in that base class so that I don't need to declare them on each derived class. That's why i can't go with interface also.
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Hi,
With static methods, this is absolutely useless.
Instead, you could use the "Singleton" pattern which restrict a class to have only one instance at a time.
To implement a class which has the singleton pattern principle, you make a sealed class with a private constructor, and the main instance which is to be accessed is a readonly static member.
For example :
sealed class Singleton
//Some methods
void Method1() { }
int Method2() { return 5; }
//The private constructor
private Singleton() { }
//And, most importantly, the only instance to be accessed
private static readonly _instance = new Singleton();
//The corresponding property for public access
public static Instance { get { return _instance; } }
And then you can access it this way :
Singleton.Instance.Method1();
Now, to have a "mold" for this, you could make an interface with the methods you want, and then implement it in a singleton class :
interface ICRUD<BaseClass>
List<BaseClass> GetList();
BaseClass Get(int ID);
bool Insert(BaseClass objB);
bool Update(int ID);
bool Delete(int ID);
And then an example of singleton class :
sealed class CRUDClassA : ICRUD<ClassA>
public List<ClassA> GetList()
//Make your own impl.
throw new NotImplementedException();
public ClassA Get(int ID)
//Make your own impl.
throw new NotImplementedException();
public bool Insert(ClassA objA)
//Make your own impl.
throw new NotImplementedException();
public bool Update(int ID)
//Make your own impl.
throw new NotImplementedException();
public bool Delete(int ID)
//Make your own impl.
throw new NotImplementedException();
private CRUDClassA() { }
private static readonly _instance = new CRUDClassA();
public static Instance { get { return _instance; } }
That should solve your problem, I think...
Philippe

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