Very confusing about passing values through pointer array among functions?? :-(

Hi,

I think my concept has a bug that I cannot handle the pointer array passing throughout function very well. Take the following code as an example:

#include <iostream.h>
#include <string.h>

class books
{
private:
char author[30];
char title[30];

public:
books() //constructor1
{
strcpy(author, "none");
strcpy(title, "none");
};

books(char auth[30], char tit[30]) //constructor2
{
strcpy(author, auth);
strcpy(title, tit);
};

~books()
{
cout << "Destructor: " << author << endl << endl;
};

void set_author(char s[30]);
void set_title(char s[30]);

void* pointer(const char* a[30]); //Am I right or wrong?
void* pointer1(const char* t[30]);

void display();
};

void books::set_author(char s[30])
{
strcpy(author, s);
}

void books::set_title(char s[30])
{
strcpy(title, s);
}

void* books::pointer(const char* a[30]) // Am I right or wrong?
{
strcpy(author, *a);
return a; //How should I set the return value?
}

void* books::pointer1(const char* t[30])
{
strcpy(title, *t);
return t;
}

void books::display()
{
cout << author << " , " << title << endl << endl;
}


int main(int argc, char* argv[])
{
books bk1, bk2, bk3("Paul", "Story book");

bk1.set_author("Raymond"); //through base class public function to access the data members

bk1.set_title("Eye on HK");

bk1.display();

bk2.display(); //constructor 1 (call constructor 1)

bk3.display(); //constructor 2 (call constructor 2)

books *bk4 = new books("Peter", "Maths"); //Dynamic pointer and allocate a memory space

bk4->display();

delete bk4;

/*char x[] = "ABC";

books *bk5;*/ // Don't know how to pass char array "ABC" to the void pointer function above to set the author name???

return 0;
}


Also, is there no such thing: reference array? e.g. &x[10].

If so, reference will only deal with single int, char or string but not array??

There is pass by value - the local variables in main will not change.

pass by reference - the local variables in main will change.

How about pointer? Is it a kind of pass by reference? I messed up these stuff. Anyone could give me an example like the above how to pass pointer between main and function? and when should I use it?

Thank you very much.

gogo



:confused:

#icnlude <iostream.h>
#icnlude <string.h>

void changeName(char*);

int main()
{
char * name = new char[80];
strcpy(name, "Howdy Doody");
changeName(name);
cout << name;
delete [] name;
name = NULL;
return 0;
}

void changeName(char * Name)
{
strcpy(Name, "Walker, Texas Ranger");
}

should put Walker, Texas Ranger to the screen.

Use pass by value if you don't want function to change value of passed variable and pass by reference using a reference or a pointer if you do want to change the value of the passed variable or if the variable is large and therefore you save time (not much, but a little) by not having to create a copy of the passed variable to use in the function.

char * name = new char[80];
strcpy(name, "Howdy Doody");
changeName(name);

I found that the above code cannot change the name of the function and name cannot be null as it is not int.

I want to know that:

When I created a private data member which is char array type like my example: char author[30], char title[30], and I have a function which accepts pointer notation when passing arrays like

void point(char* x, char* y)
{
author = x;
title = y; // I knew they are wrong and how can I set them?
}

and in the

int main()
{
//How can I pass the char pointer array to the above function which in turn change the values of private data members: author[30] and title[30]?

books object, *ptr;
ptr = &object;

ptr->point("Ivor", "Java 2");

//I tried this but failed. How should I pass them? I know how to use the dynamic pointer char * name = new char[80] with there are no pointer in the void function. However, how should I set them if there are pointer in the void function? void point(char* x, char* y).

return 0;

}

Pointer + array + passing function + access private data members made me crazy.

Any help ?????

Thanks a lot.

gogo




:eek: