Re: Reference a struct member variable - C / C++ / MFC Discussion Boards

Re: Reference a struct member variable

manoharbalu17-May-12 4:40

manoharbalu

17-May-12 4:40

Yes I need that.

Re: Reference a struct member variable

Albert Holguin17-May-12 8:02

Albert Holguin

17-May-12 8:02

That's a great question...

Re: Reference a struct member variable

Erudite_Eric17-May-12 19:36

Erudite_Eric

17-May-12 19:36

yeah, and he will probably declare them on the stack.....

==============================

Nothing to say.

Re: Reference a struct member variable

Aescleal17-May-12 4:19

Aescleal

17-May-12 4:19

- Replace test1::IV with a pointer to float
- Replace test1::NENTH with a pointer to float
- Add a constructor for test1 that takes a test2 by reference and set up the pointers in there

As Richard said are you sure you want that size of object kicking around? And are you sure you want one object to interfere directly with the internals of another object? That usually leads to tears and breaking an object's invariant.

Cheers,

Ash

Edit as I forgot the important bit in italics

Re: Reference a struct member variable

TomasRiker217-May-12 7:36

TomasRiker2

17-May-12 7:36

Here you see that arrays and pointers are not quite the same although they behave almost similarly. You can't change the address of an array once it was created.

Visit my project: Derivative Calculator

Re: Reference a struct member variable

Erudite_Eric17-May-12 19:38

Erudite_Eric

17-May-12 19:38

As others suggest, you need pointers, but if you really have common data shared between two structs then take it out of them and put it in a third struct.

==============================

Nothing to say.

Re: Reference a struct member variable

Aescleal17-May-12 21:10

Aescleal

17-May-12 21:10

A far better way of doing things than I suggested.

Cheers,

Ash

Re: Reference a struct member variable

Stefan_Lang21-May-12 23:50

Stefan_Lang

21-May-12 23:50

I suggest you go with the suggestion of Erudite_Erik. I took the liberty to put it into code:

C++

struct testsub
{
    float IV [300];
    float NENTH [600];
};

struct test1
{
    // constructor:
    test1(float* iv, float* nenth)
      : IV(iv), NENTH(nenth)    // this initializes the pointer variables
    {
    }

    float* IV;
    char FAIL [200];
    char FD [600];
    float* NENTH;
    float NKVAL [30][600];
    float NLEVEL [600];
    int COUNT;
    int CTIME;
    };

struct test2
{
    // constructor:
    test2(float* iv, float* nenth)
      : RIV(iv), RNENTH(nenth)    // this initializes the pointer variables
    {
    }

    float* RIV;
    float RXX [100];
    char RFAIL [200];
    char RFD [600];
    float RTB [50];
    float* RNENTH;
    char GCD [200];
    float RNKVAL [30][600];
    char MTBD [600];
    float RNLEVEL [600];
    int RCOUNT;
    int RCTIME;
};


void foo()
{
    // allocate objects
    struct testsub * sub = new testsub();
    struct test1 *sim1 = new test1(sub->IV, sub->NENTH);
    struct test2 *sim2 = new test2(sub->IV, sub->NENTH);

    // now do some stuff
    // ...

    // now release memory
    delete sim2;
    delete sim1;
    delete sub;
}

need help in MFC

jawadali47716-May-12 19:46

jawadali477

16-May-12 19:46

hi,
i have developed console program in C language running fine. the program is used to communicate to a motor through serial port. now i wanted to build GUI in MFC vs2008 (some of which i have completed). i'm facing problem in opening serial port as i have done in console program. can any one tell how to implement console program for opening serial port. code below shows how i open serial port in console program.

int COMportNum, BaudRate;
        char COMportName[256], tmpChar;
        portstream_fd COMstream;
        char COMportPrefix[10] = "COM";

COMportName[0] = ' ';
     while (COMportName[0] == ' ') {
         printf("\nEnter the %s port number the motor is attached to: ", COMportPrefix);
         scanf("%d", &COMportNum);
         printf("You selected %s%d. Is this OK? (enter 'y' or 'n'): ", COMportPrefix, COMportNum);
         tmpChar = 'f';
         while ( (tmpChar != 'y') && (tmpChar != 'n') )
               tmpChar = ((char) tolower(getchar()));
         if ( tmpChar == 'y' )
            sprintf(COMportName, "%s%d", COMportPrefix, COMportNum);
     }
     tmpChar = 'f';
     while (tmpChar != 'y') {
         printf("\nEnter the baud rate the motor communicate at (default: 9600): ");
         scanf("%d", &BaudRate);
         printf("You selected %d. Is this OK? (enter 'y' or 'n'): ", BaudRate);
         tmpChar = 'f';
         while ( (tmpChar != 'y') && (tmpChar != 'n') )
               tmpChar = ((char) tolower(getchar()));
     }


     /* initialize the serial port */
     set_baud_rate(BaudRate);
     COMstream = open_host_port(COMportName);

     if ( COMstream == PORT_NOT_OPENED )
         { printf("\nSerial Port setup error.\n");
           goto abnormal_exit;  }
     printf("\nSerial port %s initialized\n", COMportName);