Thread: String array question

Hi,

I have a question regarding the string array.

Here is the header file:

#include <iostream>
#include <string>
#define SIZE 100
using namespace std;

class bookmarks
{
private:
string url[SIZE];
string title[SIZE];

public:
bookmarks();
void setbookmarks(string& x[], string& y[]); //how should I set?
string getbookmarks();
};


Here is the implementation file:

#include <iostream>
#include "bookmarks.h"
#include <string>
#define SIZE 100
using namespace std;

bookmarks::bookmarks()
{
url[] = ""; //how should I set initialize all elements to be null?
title[] = "";
}

void bookmarks::setbookmarks(string& x[], string& y[])
{
url = x; //how should I set?
title = y;
}

string bookmarks::getbookmarks()
{
int i;
cout << " URL Page Title";
for (i = 0; i < SIZE; i++)
cout << url[i];
cout << " ";
cout << title[i];
cout << endl;
}

Thanks

gogo

I changed the code: (I also tried *x, *y)

bookmarks::bookmarks()
{
memset(url, NULL, SIZE);
memset(title, NULL, SIZE);
}

void bookmarks::setbookmarks(string& x, string& y)
{
strncpy(url, x, SIZE);
strncpy(title, y, SIZE);
}

There are 2 identical errors:

error C2664: 'strncpy' : cannot convert parameter 1 from 'class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > [100]' to 'char *'
Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast

Thanks for help.

gogo

instances of the string class cannot be null, but they can be empty. in your constructor try this:

bookmarks::bookmarks()
{
int i;
for(i = 0; i < size; i++)
{
url[i] = "";
title[i] = "";
}

strcpy and it's relatives like strncpy only work with c_style strings, not instances of string classes such as you use in the arrays url and title.

void bookmarks::setbookmarks(string& x, string& y, int i)
{
url[i] = x;
title[i] = y;
}

I think you are getting confused over the various types of strings, a word that is used in many contexts in C++.

Hi,

I knew that char * can be used to read words and it must be used with strcpy. But, I am doubted that whether it can be done with the array? e.g. char x[20], char *y, strcpy(x, y). Then, the address of the passed word will be passed to y. If I have 10 inputs for the word, could I also use char x[20]?

or I need to use 2D arrays - char[][20] instead?

Anyway, I don't want to use char. I have to use string.

Also, Guest's suggestion is close but still has one error. I need to specify x and y are constants like void bookmarks::setbookmarks(const string& x, const string& y, int i). Otherwise, it will be an error.

Now, I have 2 directions to accomplish it, but both failed:

Case 1:

main program - created an object and called the functions:

void main()
{
bookmarks x;
x.setbookmarks();
x.getbookmarks();
}

implementation -

bookmarks::bookmarks() //all arrays are initialized.
{
int i;
for(i = 0; i < SIZE; i++)
{
url[i] = "";
title[i] = "";
}
}

void bookmarks::setbookmarks() //here is the problem - it shows nothing on the console screen for inputation.
{
string x;
string y;
int j=0;
url[j] = x;
title[j] = y;
for(j = 0; j < SIZE; j++)
{
cin >> "Input URL : " >> x;
cout << endl;
cin >> "Input Title : " >> y;
cout << endl;
}
}

void bookmarks::getbookmarks()
{
int i;
cout << " URL Page Title" << endl;
for (i = 0; i < SIZE; i++)
{
cout << url[i] << " " << title[i] << endl;
}
cout << endl;
}


Case 2:

A simplied model without string array:

here is the header file:

#include <iostream>
#include <string>
using namespace std;

class bookmarks
{
private:
string url; // no array this time
string title;

public:
bookmarks();
void setbookmarks();
void getbookmarks();
};


Here is the implementation:

bookmarks::bookmarks()
{
url = ""; //initialized null value
title = "";
}

void bookmarks::setbookmarks() // Here is the same problem with the string array code, it shows nothing.
{
string x;
string y;
url = x;
title = y;
cin >> "Input URL : " >> x;
cout << endl;
cin >> "Input Title : " >> y;
cout << endl;
}

void bookmarks::getbookmarks()
{
cout << "URL : " << url << " " << "Title : " << title << endl;
}

Main program:

void main()
{
bookmarks x;
x.setbookmarks();
x.getbookmarks();
}

My teacher gave a hint to me that to create a bookmarks type of array in order to get continuous input from user.

e.g. bookmarks x[100];

And, you can print out each array like object.

But, I think I have to fix the inputation problem first. If any hint for the bookmarks array, pls let me know.

Regards

gogo

Sorry, I made a big mistake for the inputation.

cout << "Input URL : ";
cin >> x;
cout << endl;
cout << "Input Title : ";
cin >> y;
cout << endl;

Thanks for help.

gogo