Thread: Accessing Private Variables in Structures

Hello,
this is my first C++ assignment so please bear with me. I need to translate a C program to C by making variables in structures private(no classes yet!) and putting public inline functions. There's a good chance that I have much more problems with my code than I'm asking right now, but I have 4 spots that I'm currently stuck in and can't access properly.

My structures:

Code:

struct Container 
{
private:
    int count;
    char** lines;    
    int nlines;    
public:
    int getCount(){ return count;}


    void setCount( ){ count = 0;}
    
    int getLineCount(){ return nlines;}
    
    char* getLine(int count){ return *(lines+count);}
    
    int addLine(char* line){
        *(lines + count++) = makeString(line);
        return nlines;
    }
    void deleteFile()
    {
        int x = 0;
        if (lines)
        {
            for(x = 0; x < nlines; x++) 
                free(*(lines + x));
            free(lines);
        }
        //free(container); DON'T KNOW IF I NEED THIS!!
    }
};

Code:

struct FileHandler
{
private:
    FILE* fpointer;
    struct Container* container;
public:
    int countLines(FILE* fpointer){
        int count = 0;
        char line[ONEK];
        if (fpointer != NULL)
        {
            while (!feof(fpointer))
                if (fgets(line, ONEK, fpointer)) count++;
            rewind(fpointer);    
        }
        return count;
        }


    void initContainer(){
    int count = countLines(fpointer);
    container = (struct Container*)malloc(sizeof(struct Container));
    container->setCount();
    container->getLineCount.nlines = count; // Problem #1 (both this problem and the one below throws error "left of must contain     class/struct/union
    container->getLine.lines = (char**)malloc( sizeof(char*)*container->addLine->nlines ); // Problem #2
    }
}

Code:

struct Inventory 
{
private:
    Book* books;        //an array of books
    int nbooks;        //num of books in inventory
public:
int fillInventory(struct Container* cp){		int current = 0;
		initInventory(cp->getLineCount());
		if (cp != NULL) 
		{
		for (current = 0; current < cp->getLineCount(); current++)
			books->initBook( (char*)(books + current), *(cp)->getLine(current)); //NO IDEA MOST LIKELY WRONG!
		}
		return nbooks;
	}
void deleteInventory(){
        if (books) 
        {
            int x;
            for (x = 0; x < nbooks; x++)
                books->deleteBook((int)books + x);  // DON'T KNOW
            free(books);
        }
    }
};

And in my main:

Code:

void main()
{   
        struct FileHandler fhandle;        
        struct Inventory inventory;
        printf("Processing File from: %s\n", FILE_NAME);        
        if (fhandle.processFile(FILE_NAME))
        {
            printf("Filling Inventory....\n");    
            inventory.fillInventory();        //Problem #3 (it needs to take struct Container cp, should I just add it in main?)
            inventory.showInventory();        
            printf("Cleaning up....\n");
            inventory.deleteInventory();    
            deleteFile(fhandle.container); //Problem #4 (no idea how to access)
        }
}

-Thank you for your time. Any tips or suggestions are greatly appreciated!

Originally Posted by hotshotennis

...I need to translate a C program to C...

Just confirming C -> C++?
If so, you could start by getting rid of all C stuff, fgets (std::getline), printf (std::cout), malloc and free (std::vector, std::array), stop using heap allocation (use stack allocation), get rid of "struct" before struct types (eg struct FileHandler -> FileHandler), char arrays (std::string).

It will make your program easier. Less to code, easier to read, harder to get wrong, and faster. Plus you will learn how to do things the C++ way.

Originally Posted by hotshotennis

The structures shouldn't be turned into classes yet either.
Anyway, if I get rid of the "struct" before it, it throws an error. The assignment does specify to get rid of any typedefs, but I don't see any.

You misunderstood Elysia's point (or one of them, anyway).

Given a type definition like

Code:

struct SomeType
{
     /*   members here */
};

the declaration of a variable of that type in C is;

Code:

struct SomeType x;

In C++, the struct keyword is not needed when declaring a variable. It still required in the type definition though.


By the way, main() returns int, not void. In both C and C++.

It is a bad habit to explicit type conversions (aka type casts) to shut up the C++ compiler. Several of the places where you use type conversions are INVALID - the compiler might accept them, but any attempt to use the result causes undefined behaviour.

For many reasons, using malloc() to dynamically allocate struct/class types in C++ is a REALLY BAD IDEA. There are lots of scenarios where it simply does not work

Originally Posted by hotshotennis

The structures shouldn't be turned into classes yet either.
Anyway, if I get rid of the "struct" before it, it throws an error. The assignment does specify to get rid of any typedefs, but I don't see any.

You misunderstood Elysia's point (or one of them, anyway).

Given a type definition like

Code:

struct SomeType
{
     /*   members here */
};

the declaration of a variable of that type in C is;

Code:

struct SomeType x;

In C++, the struct keyword is not needed when declaring a variable. It still required in the type definition though.


By the way, main() returns int, not void. In both C and C++.

It is a VERY bad habit to use explicit type conversions (aka type casts) to shut up the C++ compiler. Several of the places where you use type conversions are INVALID - the compiler might accept them, but any attempt to use the result causes undefined behaviour. If the compiler is complaining where you have used a type conversion (and I can see, on a quick look) one instance where it will, it means you have converted to the wrong type.

For many reasons, using malloc() to dynamically allocate struct/class types in C++ is a REALLY BAD IDEA. There are lots of scenarios where it simply does not work