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opening files in classes

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opening files in classes

Oct 2nd, 2005

excuse me as i am new to programming and trying to learn

i have searched through previous forum groups on this topic and i wish to seek the help of all tthe experts out there...
i wish to input a file into a class
i found this example

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
#include <iostream>
#include <string>
#include <sstream>
#include <fstream>
using namespace std;
 
class job
{
   string  name;
   int     length, time;
   string  type;
   char    urgent;
public:
   bool read(string &line)
   {
      istringstream iss(line);
      return iss >> name >> length >> time >> type >> urgent;
   }
   void show()
   {
      cout << "name   = " << name   << '\n';
      cout << "length = " << length << '\n';
      cout << "time   = " << time   << '\n';
      cout << "type   = " << type   << '\n';
      cout << "urgent = " << urgent << '\n';
      cout << endl;
   }
};
 
int main()
{
   ifstream iFile("input1.txt");
   if ( iFile )
   {
      string line;
      while ( getline(iFile, line) )
      {
         job myjob;
         if ( myjob.read(line) )
         {
            myjob.show();
         }
      }
   }
   return 0;
}
#include <iostream>
#include <string>
#include <sstream>
#include <fstream>
using namespace std;

class job
{
   string  name;
   int     length, time;
   string  type;
   char    urgent;
public:
   bool read(string &line)
   {
      istringstream iss(line);
      return iss >> name >> length >> time >> type >> urgent;
   }
   void show()
   {
      cout << "name   = " << name   << '\n';
      cout << "length = " << length << '\n';
      cout << "time   = " << time   << '\n';
      cout << "type   = " << type   << '\n';
      cout << "urgent = " << urgent << '\n';
      cout << endl;
   }
};

int main()
{
   ifstream iFile("input1.txt");
   if ( iFile )
   {
      string line;
      while ( getline(iFile, line) )
      {
         job myjob;
         if ( myjob.read(line) )
         {
            myjob.show();
         }
      }
   }
   return 0;
}

but it only works if the format looks like this

 Help with Code Tags 
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BAK 90001 200 TXT N
CRSC 90010 150 TXT N
MARY 90011 140 FP N
CARL240 90050 300 FP N
LOW236 90052 150 FP N
BAK 90001 200 TXT N
CRSC 90010 150 TXT N
MARY 90011 140 FP N
CARL240 90050 300 FP N
LOW236 90052 150 FP N

where the space is the next variable

how would i manipulate this code if my stucture was on a per line basis as opposed to a space basis for the variable?
e.g.

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
bak
90001
200
txt
n
CRSC
90010
150
TXT
N
bak
90001
200
txt
n
CRSC
90010
150
TXT
N

i need it to read the WHOLE line... as the name may or may not have a first and/or last name

thanks in adavance

Last edited by Dave Sinkula; Oct 2nd, 2005 at 11:25 pm. Reason: Added [code][/code] tags.

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Re: opening files in classes

Oct 2nd, 2005

understand what the code is doing. In main you make an input file and read it a line at a time. You then pass that line to myjob::read. This is where the parsing occurs. first an istringstream is constructed from our line of input then several items are extracted from it. This works the same as extracting items from cin but instead of a keyboard for input it reads from a string. Now have a go at solving your problem. How would you do it if you was reading from cin. you do the same with a stringstream.

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Re: opening files in classes

Oct 3rd, 2005

•

Originally Posted by Stoned_coder

understand what the code is doing. In main you make an input file and read it a line at a time. You then pass that line to myjob::read. This is where the parsing occurs. first an istringstream is constructed from our line of input then several items are extracted from it. This works the same as extracting items from cin but instead of a keyboard for input it reads from a string. Now have a go at solving your problem. How would you do it if you was reading from cin. you do the same with a stringstream.

like i said i am very ver new to this...
but that makes logical sense
if i was reading from cin...
i would go something like
iss.cin << name << length << time << type << urgent;
is this correct....?
would i be right in therefore thinking ...
iss.istringstream << name << length << time << type << urgent;

but how would i get each line to read to say about 5 lines per class?

btw thanks for the help

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long time no c

Re: opening files in classes

Oct 3rd, 2005

Minor tweaks:

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(Toggle Plain Text)

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

class job
{
   string  name;
   int     length, time;
   string  type;
   char    urgent;
public:
   bool read(ifstream &file)
   {
      return file >> name >> length >> time >> type >> urgent;
   }
   void show()
   {
      cout << "name   = " << name   << '\n';
      cout << "length = " << length << '\n';
      cout << "time   = " << time   << '\n';
      cout << "type   = " << type   << '\n';
      cout << "urgent = " << urgent << '\n';
      cout << endl;
   }
};

int main()
{
   ifstream iFile("file.txt");
   if ( iFile )
   {
      job myjob;
      while ( myjob.read(iFile) )
      {
         myjob.show();
      }
   }
   return 0;
}

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Re: opening files in classes

Oct 4th, 2005

mate your a legend... it was frustrating me something severe..!

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Re: opening files in classes

Oct 4th, 2005

•

Originally Posted by Dave Sinkula

Minor tweaks:
Help with Code Tags

(Toggle Plain Text)
#include <iostream>
#include <string>
#include <sstream>
#include <fstream>
using namespace std;

class job
{
   string  name;
   int     length, time;
   string  type;
   char    urgent;
public:
   bool read(ifstream &file)
   {
      return file >> name >> length >> time >> type >> urgent;
   }
   void show()
   {
      cout << "name   = " << name   << '\n';
      cout << "length = " << length << '\n';
      cout << "time   = " << time   << '\n';
      cout << "type   = " << type   << '\n';
      cout << "urgent = " << urgent << '\n';
      cout << endl;
   }
};

int main()
{
   ifstream iFile("file.txt");
   if ( iFile )
   {
      job myjob;
      while ( myjob.read(iFile) )
      {
         myjob.show();
      }
   }
   return 0;
}
#include <iostream> #include <string> #include <sstream> #include <fstream> using namespace std; class job { string name; int length, time; string type; char urgent; public: bool read(ifstream &file) { return file >> name >> length >> time >> type >> urgent; } void show() { cout << "name = " << name << '\n'; cout << "length = " << length << '\n'; cout << "time = " << time << '\n'; cout << "type = " << type << '\n'; cout << "urgent = " << urgent << '\n'; cout << endl; } }; int main() { ifstream iFile("file.txt"); if ( iFile ) { job myjob; while ( myjob.read(iFile) ) { myjob.show(); } } return 0; }

sorry one more question...
maybe i didnt make myself clear eariler...
if i have more then one record.... say about 10 records for the entire file

and want to be able to manipluate them individually... the code above only lets me edit the final class ....
e.g. aka myjob
if wanted to say declare 10 records whats the best way to do it
and how would that implement
e.g.

]#include <iostream>
#include <string>
#include <sstream>
#include <fstream>
using namespace std;

class job
{
string name;
int length, time;
string type;
char urgent;
public:
bool read(ifstream &file)
{
return file >> name >> length >> time >> type >> urgent;
}
void show()
{
cout << "name = " << name << '\n';
cout << "length = " << length << '\n';
cout << "time = " << time << '\n';
cout << "type = " << type << '\n';
cout << "urgent = " << urgent << '\n';
cout << endl;
}
};

int main()
{
ifstream iFile("file.txt");
if ( iFile )
{
job myjob, myjob1, myjob2, myjob3, myjob4; //..etc;
while ( myjob.read(iFile) )
{

}
while ( myjob1.read(iFile) ) //etc...
{

}
myjob.show();
myjob1.show();
myjob2.show();
myjob3.show(); //etc...
}
return 0;

like i said eariler what is a good way to code this?

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long time no c

Re: opening files in classes

Oct 4th, 2005

•

Originally Posted by bobobobo51

if i have more then one record.... say about 10 records for the entire file

and want to be able to manipluate them individually... the code above only lets me edit the final class ....
e.g. aka myjob
if wanted to say declare 10 records whats the best way to do it
and how would that implement

You're pretty much hinting that you want an array of 10. First, let me make this change (so I can be really lazy later on).

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(Toggle Plain Text)

class job
{
   string  name;
   int     length, time;
   string  type;
   char    urgent;
public:
   bool read(ifstream &file)
   {
      return file >> name >> length >> time >> type >> urgent;
   }
   friend ostream& operator<< (ostream &o, const job &j);
};

ostream& operator<< (ostream &o, const job &j)
{
   o << "name   = " << j.name   << '\n';
   o << "length = " << j.length << '\n';
   o << "time   = " << j.time   << '\n';
   o << "type   = " << j.type   << '\n';
   o << "urgent = " << j.urgent << '\n';
   o << endl;
   return o;
}

Then after you've opened the file, you might have something like this.

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
      job myjob[10];
      for ( size_t i = 0; i < sizeof myjob / sizeof *myjob; ++i )
      {
         if ( !myjob[i].read(iFile) )
         {
            break;
         }
         cout << myjob[i];
      }
      job myjob[10];
      for ( size_t i = 0; i < sizeof myjob / sizeof *myjob; ++i )
      {
         if ( !myjob[i].read(iFile) )
         {
            break;
         }
         cout << myjob[i];
      }

But if you really don't want to hard-code a size of 10, I'd say use a vector.

Some additional headers are necessary for this example:

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#include <vector>
#include <algorithm>
#include <iterator>
#include <vector>
#include <algorithm>
#include <iterator>

Now after the file is opened, code to read and display it might be as follows.

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 C++ Syntax (Toggle Plain Text) 
      job ajob;
      vector<job> myjob;
      while ( ajob.read(iFile) )
      {
         myjob.push_back(ajob);
      }
      copy(myjob.begin(), myjob.end(), ostream_iterator<job>(cout, "\n"));
      job ajob;
      vector<job> myjob;
      while ( ajob.read(iFile) )
      {
         myjob.push_back(ajob);
      }
      copy(myjob.begin(), myjob.end(), ostream_iterator<job>(cout, "\n"));

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Re: opening files in classes

Oct 4th, 2005

thanks mate ive learnt sooo much in the past couple days...

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Re: opening files in classes

Oct 5th, 2005

ok... is it okay if i you help me expand my knowledge even more?
take a different example...
say i got a file of swimmers

e.g.

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
M
100 Free		
50.24
Ian Thorpe
10/12/1960
10/02/2005
Wagga Wagga
1
M
100 Free
51.01
Grant Hackett
20/07/69
12/03/2005
Melbourne
2
M
100 Free
52.00
John Konrads
22/10/1970
14/04/2005
Adelaide
3
M
100 Free		
50.24
Ian Thorpe
10/12/1960
10/02/2005
Wagga Wagga
1
M
100 Free
51.01
Grant Hackett
20/07/69
12/03/2005
Melbourne
2
M
100 Free
52.00
John Konrads
22/10/1970
14/04/2005
Adelaide
3

where the lines read

 Help with Code Tags 
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Sex					M
Event				eg	100 Free		
Performance				50.24
Name					Ian Thorpe
Date of birth				10/12/1960
Data of competition			10/2/2005
Venue					Wagga Wagga
Position				1
Sex					M
Event				eg	100 Free		
Performance				50.24
Name					Ian Thorpe
Date of birth				10/12/1960
Data of competition			10/2/2005
Venue					Wagga Wagga
Position				1

lets make it interesting and say... we can put those files into a struct ...
e.g.

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#include <iomanip>
#include <fstream>
#include <iostream>
 
using namespace std;
 
 
int main(){
fstream fs;
int const MAX = 11;
struct swim
{
    char sex[2];
    char eventtype[20];
    char perf[20];
    char name[20];
    char dob[11];
    char doc[11];
    char venue[20];
    char position[2];
};
 
swim record[MAX];
 
int count=0;
fs.open("c:\\swimmers.txt", ios::in);
if(fs.fail()) return 2;
 
	while (!fs.eof() && count < MAX)
    {
 
fs.getline(record[count].sex,2,'\n');
for(int i=0; i<1;i++) 
fs.getline(record[count].eventtype,20,'\n');
for(int i=0; i<1;i++) 
fs.getline(record[count].perf,20,'\n');
for(int i=0; i<1;i++)
fs.getline(record[count].name,21,'\n');
for(int i=0; i<1;i++)
fs.getline(record[count].doc,11,'\n');
for(int i=0; i<1;i++)
fs.getline(record[count].dob,11,'\n');
for(int i=0; i<1;i++)
fs.getline(record[count].venue,21,'\n');
for(int i=0; i<1;i++)
fs.getline(record[count].position,2,'\n');
for(int i=0; i<1;i++)
 
cout << record[count].sex << "\n";
cout << record[count].eventtype << "\n";
cout << record[count].perf << "\n";
cout << record[count].name << "\n";
cout << record[count].doc << "\n";
cout << record[count].dob << "\n";
cout << record[count].venue << "\n";
cout << record[count].position << "\n";
 
count++;
 
fs.close();
cout << record[6].name;
 
system("pause");
return 0;
}
#include <iomanip>
#include <fstream>
#include <iostream>

using namespace std;


int main(){
fstream fs;
int const MAX = 11;
struct swim
{
    char sex[2];
    char eventtype[20];
    char perf[20];
    char name[20];
    char dob[11];
    char doc[11];
    char venue[20];
    char position[2];
};

swim record[MAX];

int count=0;
fs.open("c:\\swimmers.txt", ios::in);
if(fs.fail()) return 2;

	while (!fs.eof() && count < MAX)
    {

fs.getline(record[count].sex,2,'\n');
for(int i=0; i<1;i++) 
fs.getline(record[count].eventtype,20,'\n');
for(int i=0; i<1;i++) 
fs.getline(record[count].perf,20,'\n');
for(int i=0; i<1;i++)
fs.getline(record[count].name,21,'\n');
for(int i=0; i<1;i++)
fs.getline(record[count].doc,11,'\n');
for(int i=0; i<1;i++)
fs.getline(record[count].dob,11,'\n');
for(int i=0; i<1;i++)
fs.getline(record[count].venue,21,'\n');
for(int i=0; i<1;i++)
fs.getline(record[count].position,2,'\n');
for(int i=0; i<1;i++)

cout << record[count].sex << "\n";
cout << record[count].eventtype << "\n";
cout << record[count].perf << "\n";
cout << record[count].name << "\n";
cout << record[count].doc << "\n";
cout << record[count].dob << "\n";
cout << record[count].venue << "\n";
cout << record[count].position << "\n";

count++;

fs.close();
cout << record[6].name;

system("pause");
return 0;
}

<< moderator edit: added code tags: [code][/code] >>

and i wanna make classes BASED on the events e.g.
Men or women denoted by M or W.The events are 100m Free, 200m Back, 400m Medley, 800m Back, 1500m Free.
therefore in total 10 classes...
and inside those classes i got a struct of each swimmer with the apprioate event
i was thinking something along the lines of

 Help with Code Tags 
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struct athlete{
name
performance
dob
doc
venue
position
}
 
 
struct record{
sex
event
name
performance
dob
doc
venue
position
}
const int MAXSIZE = 10;
class rank
{
string sex, event;
athlete data[maxsize];
int total;
public
rank (string &s, string &e);
string getsex();
string getevent();
int gettotal();
althelete 7getdata(int i );
void sort();
void add();
void replace(int, athlete&);
void remove(int position);
friend ostream &operator<<(ostream&, const rank&):
void save(ostream&);
};
struct athlete{
name
performance
dob
doc
venue
position
}


struct record{
sex
event
name
performance
dob
doc
venue
position
}
const int MAXSIZE = 10;
class rank
{
string sex, event;
athlete data[maxsize];
int total;
public
rank (string &s, string &e);
string getsex();
string getevent();
int gettotal();
althelete 7getdata(int i );
void sort();
void add();
void replace(int, athlete&);
void remove(int position);
friend ostream &operator<<(ostream&, const rank&):
void save(ostream&);
};

so a user is prompted with an option of selecting 1) to select the event of the class.... e.g. 100 free male
when selected given the option to edit it
therefore when an event is selected in option 1 the appropriate object should be selected. Option 2 will involve searching the list of swimmers names in the object

whats a good way of approching this??
i was thinking develop a class and functions similar to the above...
with the apprioprate structs....
am i on the right track? any thoughts?

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Re: opening files in classes

#10

Oct 6th, 2005

Ah, if only I had more time to spend...

First thing I'd recommend is using std::string [note to Dani: here again is where I'd prefer a fixed font] instead of a char array; perhaps numeric fields where appropriate. Put them in your class or struct -- let's call it a record. Taking input for a record could a number of lines, similar to previous posts. And again use use::vector. Something like that. And there's this.