Reference a struct member variable

manoharbalu

I have 2 different structures test1 and test2 struct test1 { float IV [300]; char FAIL [200]; char FD [600]; float NENTH [600]; float NKVAL [30][600]; float NLEVEL [600]; int COUNT; int CTIME; }; struct test2 { float RIV [300]; float RXX [100]; char RFAIL [200]; char RFD [600]; float RTB [50]; float RNENTH [600]; char GCD [200]; float RNKVAL [30][600]; char MTBD [600]; float RNLEVEL [600]; int RCOUNT; int RCTIME; }; The 2 structure objects are: struct test1 *sim1; struct test2 *sim2; sim1 = new test1(); sim2 = new test2(); Now I want the sim1->IV to exactly point to sim2->RIV and sim1->NENTH to exactly point to sim2->RNENTH. So at any point of time, sim1->IV[i] should be same as sim2->RIV[i] where i is any of the valid index range and similarly for NENTH and RNENTH. Any one know how to acheive this please provide me the code.

C.B.Mohankumar

Chris Losinger

manoharbalu wrote:

Now I want the sim1->IV to exactly point to sim2->RIV

so you need to do this:

struct test1
{
float *IV;
...

and when you create a test1 object, you have to set the pointer to a test2's RIV array:

sim1 = new test1();
sim2 = new test2();
sim1->IV = &sim2->RIV[0];

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CPallini

manoharbalu wrote:

Now I want the sim1->IV to exactly point to sim2->RIV
and sim1->NENTH to exactly point to sim2->RNENTH.

If you need a pointer then use a pointer:

struct test1
{
float * IV;
//...
float * NENTH;
//...
};
//...

test1 *sim1;
test2 *sim2;

sim2 = new test2();
sim1 = new test1();
sim1->IV = sim2->RIV;
sim1->NENTH = sim2->RNENTH;

Veni, vidi, vici.

Lost User

You have something over 20,000 floats in each of your structures; are you really sure this is what you want?

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Aescleal

- 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

manoharbalu

Yes I need that.

TomasRiker2

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.

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Albert Holguin

That's a great question...

Lost User

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

============================== Nothing to say.

Lost User

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.

Aescleal

A far better way of doing things than I suggested. Cheers, Ash

Stefan_Lang

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

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;

}