Assign value to element in dynamic array, turns out to be NULL

[RSASKA]

Hello,

I am developing code to

1. read the number of lines in a file ipFile, and store that value in ipLength
2. create a dynamic array ipArray of size ipLength
3. initialize ipArray
4. reposition the file pointer to the beginning of ipFile
5. get one line from ipFile, store it into ipAddress
6. assign ipAddress to an element of dynamic array ipArray

For debugging purposes, I want to display the contents of each element of the dynamic array. When i printf ipAddress, it is fine, however when I printf &ipArray[p], it turns up blank for each element. If I printf ipArray[p], it displays <null> for each element.

Below is my code, please guide:

int ipLength=0;

while (!ipFile.eof())

{//begin while !ipFile.eof()

getline (ipFile,ipLine);
ipLength++;

}//end while !ipFile.eof()


string *ipArray = NULL;
ipArray = new string [ipLength];

for (int i=0; i<ipLength; i++)

{//begin for loop

ipArray[i] = "";

}//end for loop

ipFile.seekg(0, ios::beg);
int p=0;

while (!ipFile.eof())

{//begin while !ipFile.eof()

getline (ipFile,ipLine);
int TempNumOne=ipLine.size();
char ipOutput[100]={0};

for (int a=0;a<=TempNumOne;a++)

{//begin for loop

ipOutput[a]=ipLine[a];

}//end for loop

sscanf(ipOutput, "%s", &ipAddress);
ipArray [p] = ipAddress;
printf ("%d. %s\n", p, ipArray[p]);
p++;

}//end while !ipFile.eof()


ipFile.close();
delete [] ipArray;
ipArray = NULL;

[Lindley]

The type of ipArray[p] is a C++ std::string. Printf is a C function, and does not understand C++ classes; it expects the argument corresponding to a &#37;s to be a const char*.

Try outputting ipArray[p].c_str(), or else do your output with cout rather than printf.

Also, I would recommend using a std::vector<std::string> rather than a dynamic array.

[Philip Nicoletti]

In the first section, you read until end of file. Once this happens, the internal
state of the stream is such that trying to use it further will fail. You need
to clear the state.

So, before doing the seekg() ...

ipFile.clear();

Also, I agree with previous post ... use a vector<string> and you can do everything
in one pass thru the file.

[GCDEF]

What do noobs have against white space? Seriously, get in the habit of putting spaces between variables and operators and anywhere else you can to make your code readable.

[RSASKA]

The type of ipArray[p] is a C++ std::string. Printf is a C function, and does not understand C++ classes; it expects the argument corresponding to a %s to be a const char*.

Try outputting ipArray[p].c_str(), or else do your output with cout rather than printf.

Also, I would recommend using a std::vector<std::string> rather than a dynamic array.

Awesome, it now works, thanks!

[MrViggy]

What do noobs have against white space? Seriously, get in the habit of putting spaces between variables and operators and anywhere else you can to make your code readable.

White space takes up space! Both on your display and on your disk!

Viggy