Visual C++ 2005 Designer

[6600gt]

Originally Posted by Gamer930

I'm pretty sure what you are trying to do is not possible. . .
Normally how it is a parent can't call methods of a child. I'm unsure why you would want create a parent in a child anyways because the child inherits the parent's methods. . . Depending on what you are planning on doing panels might be the way to go. The MSDN Help is a great tool for any programmer. The help section for Inheritance is at http://msdn.microsoft.com/library/de...nheritance.asp

I have been pouring through that help, especially the inheritance part. I think I finally get it: I was trying to inherit from a form that had already inherited it. In the MDI forms I was inheriting the children form the parent, then I was trying to inherit the parent form the children again. And this wouldn't work.

I might just have to go with panels. Only think I don't like about them is that hey are not as easy as form windows to arrange and close and open as you wish.

Any other suggestions?

[fowlerm]

Originally Posted by 6600gt

Any other suggestions?

I think what you are trying to do is call a method that is a member of the Parent class from a MDI child form of class Child. If that is not what you are trying to do then disregard the rest of this post, and I'm confused.

If you are trying call a method that is on the MDI parent form, then this has nothing to do with inheritance, other than that both classes must inherit from the System.Windows.Forms.Form class. Note that the Form class has a property called MdiParent that is a reference to the instance of the Form that is the MDI container. Now, to access methods that are members of the MDI parent, you have to cast that property as whatever class it really is. From what you posted, it would be:

Parent^ myParent = dynamic_cast<Parent^>(this->MdiParent);

From there you can call methods normally:

myParent->SomeMethod();

You do not use gcnew in this case because you don't want to create a new instance of the Parent class, you just need to use the reference and cast it correctly.

[6600gt]

Thanks.

I put this in

Main^ m = dynamic_cast<Main^>(this->MdiParent);

and I got these errors

Form3.h(268) : error C2065: 'Main' : undeclared identifier
Form3.h(268) : error C2065: 'm' : undeclared identifier
Form3.h(268) : error C2061: syntax error : identifier 'Main'

Yeah, I did put the #include "Main.h" above.

[esquared]

After reading through this (and your post from September about a similar type of issue), it's not readily apparent how your MDI project is set up. My first MDI project in VC++ took a lot of hours of hair pulling and coffee until I could readily pass information around.

If you would like, PM me and you can zip up & email me your project to look at. I'm assuming you've been using the free VC++ available from Microsoft's website?

[6600gt]

Originally Posted by esquared

If you would like, PM me and you can zip up & email me your project to look at. I'm assuming you've been using the free VC++ available from Microsoft's website?

Yea. I will PM once I figure out what I am trying to do.

I am curious to see your project setup as well. You should have a Main.h which houses the Main class declaration, and a Main.cpp for the Main class's code. You should also have a Form3.h and a Form3.cpp. You need to make sure that any code that references the Main class from the Form3 class resides in the Form3.cpp, since you can't have Main.h include Form3.h while at the same time Form3.h includes Main.h since this will cause errors.

So basically you are saying that I should put all my functions in the cpp file. I only need to really do this for the children, right? Currently, my project has everything in the header files. I was trying that but didn't know how to set it for this compiler. Thanks for the sample. This is exactly what I was looking for. When school finally ends tomorrow, I will try it out.

[esquared]

Originally Posted by 6600gt

So basically you are saying that I should put all my functions in the cpp file. I only need to really do this for the children, right? Currently, my project has everything in the header files. I was trying that but didn't know how to set it for this compiler. Thanks for the sample. This is exactly what I was looking for. When school finally ends tomorrow, I will try it out.

The short answer to your question is that function declarations should go into the header files (along with documentation of what the functions do ), and the function definitions should go in the cpp files.

The long answer is best left to some research into good programming practices, you can always start with the ubiquitous Wikipedia (http://en.wikipedia.org/wiki/Header_file) to get more information.

-Eric

[6600gt]

Thanks for all the help.

Now I have a new problem and I can't find any useful information on it.

Main^ main = dynamic_cast<Main^>(this->MdiParent);

for(count = 0; count < 10; count++)
{
number = main->serialPort1->BytesToRead; //Error
}

An unhandled exception of type 'System.NullReferenceException' occurred in GUI Control Interface.exe

Additional information: Object reference not set to an instance of an object.

This happens when I start sending some serial data form a PIC to the comp.

Searching on the internet hasn't explained it much.

[Tom Bottiglieri]

Originally Posted by 6600gt

T
This happens when I start sending some serial data form a PIC to the comp.

May I ask what type of project you are working on?

[6600gt]

Originally Posted by Tom Bottiglieri

May I ask what type of project you are working on?

It's a secret...
No, not really.

To my knowledge there is no real debugging system for the RC other than the printf statements. This program will allow you to watch 10 values(16 bit) at any given time. Each column has a list to choose form. There will be a preset of pwms, analogs, digital I/O, OI port values, etc. But there will also be some extra values, ex. X1, which when programed into the RC allows you watch any variable (16 bit or less).

Ex: x_1 = some_count = .......;

Then you select the X1 in any column and you start seeing a printf style stream of values.

Helpful when you are debugging a whole function. You can assign each variable in your function to a x_1 through x_x and watch all their values simultaneously.

The PIC is simulating an RC. (Don't have access to an RC one right now)

If I can get around to it(probably won't), the program might actually be able to control the robot using this:
(Its not done, not even close...)

[6600gt]

Originally Posted by 6600gt

Now I have a new problem and I can't find any useful information on it.

Main^ main = dynamic_cast<Main^>(this->MdiParent);

for(count = 0; count < 10; count++)
{
number = main->serialPort1->BytesToRead; //Error
}

Fails with:
An unhandled exception of type 'System.NullReferenceException' occurred in GUI Control Interface.exe

Additional information: Object reference not set to an instance of an object.
This happens when I start sending some serial data form a PIC to the comp.

Searching on the internet hasn't explained it much.

Anyone?

[chris31]

Originally Posted by 6600gt

Anyone?

I dont know VC++ but heres my ideas. Do a try catch and see if that give you an error code that means something more.

[6600gt]

Originally Posted by chris31

I dont know VC++ but heres my ideas. Do a try catch and see if that give you an error code that means something more.

I kinda tried this right now, and it didn't help.

Can someone explain what it means when such an exception is thrown?

Thanks

[Gamer930]

Originally Posted by 6600gt

Main^ main = dynamic_cast<Main^>(this->MdiParent);

for(count = 0; count < 10; count++)
{
number = main->serialPort1->BytesToRead; //Error
}

This could be couple things. . . The problem could be line before also. . .
Something isn't initialized and there is a NULL Pointer and you are trying to assign a NULL pointer to a data slot. .

Looking in this instance my guess is there isn't Serial Communications between the PIC and the computer, and that serialPort1 is probably NULL ??

My suggestion would be when you get a problem like this is set a breakpoint couple lines before the error and then run till it gets the breakpoint and do System Watches on the important variables and use the Step Over and Step Into to go step by step through the for loop. . . If something is null it normally comes up as something in red text or a value that you know isn't correct in the watch window.

[Bob22341]

Your problem comes when "child" calls "parent"

In c++ once you have included a file once, you can't do it again without causing build errors. You create a continual loop with including parent and chile again and again.

If you want to go into inheritance issues and calling parent functions you can, there is an easier way. Create another file called "parenta" and copy over all of the code from "parent" Then slightly change all of the function and class names to avoid build errors, and your almost done.

Change "child" to call "parenta" instead of "parent" and problem solved.

"parent" should include "child" which should include "parenta"

Hopefully that solves your problem

[6600gt]

Originally Posted by Bob22341

Your problem comes when "child" calls "parent"

In c++ once you have included a file once, you can't do it again without causing build errors. You create a continual loop with including parent and chile again and again.

If you want to go into inheritance issues and calling parent functions you can, there is an easier way. Create another file called "parenta" and copy over all of the code from "parent" Then slightly change all of the function and class names to avoid build errors, and your almost done.

Change "child" to call "parenta" instead of "parent" and problem solved.

"parent" should include "child" which should include "parenta"

Hopefully that solves your problem

This is not for the null reference exception, is it?

Thanks, anyway, but I think I got the original problem one fixed. The dynamic cast thing seems to be working. This program is already taking much longer than excepted...quite frustrating.

Again, thanks...I really need to get going on this thing.



Ok here is my function in DataView.cpp:

Main^ main = dynamic_cast<Main^>(this->MdiParent);

for(count = 1; count < 11; count++)
{
while(main->serialPort1->BytesToRead < 1);

value = main->serialPort1->ReadByte();
value <<= 8;
value += main->serialPort1->ReadByte();

List_Select(count, value);

} // FAILS right after this if there is line after

main->done_flag = 1; //Here
main->~Main(); //Or here if the above line is commented out

System.NullReferenceException

I don't get it: I am just calling something else form the main after the ReadByte(), but I get an Null exception.

Any Ideas?