Strictly speaking, it doesn't - is Visual Studio insisting that it should? Note that you have declared nameL and phoneL as const; can you see why there is no point in having a const that is not static?yungman said:
I agree.pbuk said:
else
{//If the file exist, read entire file into vector DirV.
file.read(reinterpret_cast<char*>(&Dir), sizeof(Dir));
do
{
DirV.push_back(Dir);
file.read(reinterpret_cast<char*>(&Dir), sizeof(Dir));
} while (!file.eof());
file.close();
}Mark44 said:
Mark44 said:
The same thought occurred to me, about what the job of a constructor should be.Vanadium 50 said:
Not being a C++ programmer, I had to spend 30 seconds with Google to learn about the break statement.Mark44 said:
Thanks for the suggestion. The reason I wrote the read like this is because I ran into problem reading the last element twice before. I did talk about this here and I wrote down in my notes to do this. Maybe this doesn't matter, but I don't want to take the chance and just put one more line.Mark44 said:
It's not just bad form. It is actually wrong as written. What if you are reading from an empty file?yungman said:
Wrong. You ARE the student, and we who respond to your questions are in the role of teacher.yungman said:
The time to remember what we've said is NOW, not some far-off time. You post your programs, and we attempt to make sense of them, despite your use of unhelpful and meaningless names.yungman said:
Using the hard drive or flash drive is totally irrelevant to what the constructor and destructor should be doing, which is creating an object and then destroying it, respectively. There should be other member functions that are tasked with filling an object with data, adding a contact, deleting a contact, etc. None of this should be done in a constructor.yungman said:
IMO you are NOT in a position to disagree with what @Vanadium 50 said, as you have nowhere near the knowledge of programming that he has. In his comment he gave a reason for his opinion - ignore it at your peril.yungman said:
jbriggs444 said:
Thanks, I have to think more, this is the starting point of the program, I am still thinking about the other add, delete, sort options. I will likely have more than one class. It's a challenge so far to put this together.jtbell said:
To clarify, I meant I am not a college student that have the whole career in front of me. Yes, I am a student here learning C++.Mark44 said:
I have to experiment more with that, I did run into problem before. What will happen reading an empty file? Is it just reading garbage or can it do damage to the file?jbriggs444 said:
I'm fairly sure that was already clear to most of us.yungman said:
Step through the code mentally, thinking through what each line will do. Let us pull that code section down here so that we can examine it more easily.yungman said:
else
{//If the file exist, read entire file into vector DirV.
file.read(reinterpret_cast<char*>(&Dir), sizeof(Dir));
do
{
DirV.push_back(Dir);
file.read(reinterpret_cast<char*>(&Dir), sizeof(Dir));
} while (!file.eof());
file.close();
}Rule: Think before you code. You want to figure out the failure modes when writing the code, not when running it.yungman said:
Read
while not EOF
Push
Read
end whilewhile (true)
read
if EOF then break
push
end whileDONE = false
while ( not DONE )
read
if not EOF
then
push
else
DONE = true
end if
end whileyungman said:
Ah, I see what you mean about writing in Distructor, that if that fails, the program is closed. So I should use member function to write to file.PeterDonis said:
jbriggs444 said:
yungman said:
Possibly I am missing something. That would seem to mean that the exit condition needs to be checked twice.Vanadium 50 said:
do {
read
if not EOF
push
end if
} while not EOFI tried your suggestion:jbriggs444 said:
jbriggs444 said:
I know, give me time to change the program, want to resolve the double read first. I still need to change the names also.Mark44 said:
#ifndef VectorCall_H
#define VectorCall_H
#include <vector>
#include <fstream>
class DirectoryClass
{
private:
const static int nameLen = 25, phoneLen = 12;
public:
struct Directory { char name[nameLen]; char phone[phoneLen]; };
std::vector<Directory>DirV;
Directory Dir; bool newF, failOpen;
std::fstream file;
bool readFile()//
{
failOpen = false;
file.open("Directory.dat", std::ios::in | std::ios::binary);
if (file.fail())
{//If file doesn't exist, create the file
std::cout << " Fail to open file.\n";
file.open("Directory.dat", std::ios::out | std::ios::binary | std::ios::app);
file.close();
failOpen = true;
}
else
{//If the file exist, read entire file into vector DirV.
while (!file.eof())
{
file.read(reinterpret_cast<char*>(&Dir), sizeof(Dir));
if (file.eof()) { break; }
DirV.push_back(Dir);
};
file.close();
}
return failOpen;
}
void createFile()
{ file.open("Directory.dat", std::ios::out | std::ios::binary | std::ios::app);
file.close(); }
void writeFile()
{
int ct2 = 0;
file.open("Directory.dat", std::ios::out | std::ios::binary);
do//write the updated data in vector DirV into the file before closing
{
file.write(reinterpret_cast<char*>(&DirV[ct2]), sizeof(DirV[ct2]));
ct2++;
} while (ct2 < DirV.size());
file.close();
}
void push_backV() { DirV.push_back(Dir); }
void print() { std::cout << "Name: " << Dir.name <<
" Phone: " << Dir.phone << "\n\n"; }
};
#endif#include <iostream>
#include <string>
#include <vector>
#include "VectorCall.h"
using namespace std;
int main()
{
char more; int index = 0; const int nameLen = 25, phoneLen = 12;
DirectoryClass Information;
char displayAll, tryAgain = false;
Information.readFile();
if (Information.failOpen == true)
{cout << " Fail to open file, want to try again? "; cin >> tryAgain;}
if (tryAgain == true) Information.readFile();
if (Information.failOpen == true)
{//First time set up the directory by entering all the names and information
cout << " File does not exist, let's create the file. " <<
"You need to enter informations:\n\n";
Information.createFile();
cin.ignore();
do
{ cout << " Enter name: "; cin.getline(Information.Dir.name, nameLen);
cout << " Enter phone: "; cin.getline(Information.Dir.phone, phoneLen);
//Info.print();
Information.push_backV();//writing into vector DirV.
cout << " Do you want to enter another name? "; cin.get(more);
cin.ignore();
} while (tolower(more) == 'y');
}
//Ask whether to display all the information in the file.
cout << " Press 'y' to see the whole list. "; cin >> displayAll;
cin.ignore(); cout << endl;
if (displayAll == tolower('y'))
{ do
{ cout << "Name stored in DirV is: " << Information.DirV[index].name <<
" phone: " << Information.DirV[index].phone << "\n\n";
index++;
} while (index < Information.DirV.size());
}
else { cout << " Bye\n\n"; }
Information.writeFile();
return 0;
}If you try to read from an empty file, you reach end-of-file immediately. I tested this with the following program:yungman said:
#include <iostream>
#include <fstream>
#include <iomanip>
using namespace std;
int main ()
{
// Open a file for output, but don't write anything to it.
// Then close it.
ofstream outputFile ("emptyfile.dat");
cout << "Trying to open emptyfile.dat for output..." << endl;
if (outputFile)
{
cout << "Successfully opened emptyfile.dat for output." << endl;
}
else
{
cout << "Failed to open emptyfile.dat for output." << endl;
}
outputFile.close();
cout << "Closed emptyfile.dat." << endl;
// Open that file for input, and try to read from it.
cout << "Trying to open emptyfile.dat for input..." << endl;
ifstream inputFile ("emptyfile.dat");
if (inputFile)
{
cout << "Successfully opened emptyfile.dat for input." << endl;
cout << "Trying to read from emptyfile.dat..." << endl;
string line;
if (getline (inputFile, line))
{
cout << "'" << line << "' was read from emptyfile.dat." << endl;
}
else
{
cout << "EOF on emptyfile.dat." << endl;
}
inputFile.close();
cout << "Closed emptyfile.dat." << endl;
}
else
{
cout << "Can't open emptyfile.dat." << endl;
}
return 0;
}Trying to open emptyfile.dat for output...
Successfully opened emptyfile.dat for output.
Closed emptyfile.dat.
Trying to open emptyfile.dat for input...
Successfully opened emptyfile.dat for input.
Trying to read from emptyfile.dat...
EOF on emptyfile.dat.
Closed emptyfile.dat.