в 14:21, 25 мая 2010

2010-05-25T14:21:06Z

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2010-05-25T10:24:07Z

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==Save and read class back and forth to a file==

<source lang="cpp">
#include <iostream>
#include <fstream>
#include <cstring>
using namespace std;
class Person {
char name[80];
char areaCode[4];
char prefix[4];
char num[5];
public:
Person() { };
Person(char *n, char *a, char *p, char *nm)
{
strcpy(name, n);
strcpy(areaCode, a);
strcpy(prefix, p);
strcpy(num, nm);
}
friend ostream &operator<<(ostream &stream, Person o);
friend istream &operator>>(istream &stream, Person &o);
};
ostream &operator<<(ostream &stream, Person o)
{
stream << o.name << " ";
stream << "(" << o.areaCode << ") ";
stream << o.prefix << "-";
stream << o.num << endl;
return stream; // must return stream
}
istream &operator>>(istream &stream, Person &o)
{
cout << "Enter name: ";
stream >> o.name;
cout << "Enter area code: ";
stream >> o.areaCode;
cout << "Enter prefix: ";
stream >> o.prefix;
cout << "Enter number: ";
stream >> o.num;
cout << endl;
return stream;
}
int main()
{
Person personObject;
char c;
fstream pb("phone", ios::in | ios::out | ios::app);
if(!pb) {
cout << "Cannot open phone book file.\n";
return 1;
}
for(;;) {
do {
cout << "1. Enter numbers\n";
cout << "2. Display numbers\n";
cout << "3. Quit\n";
cout << "\nEnter a choice: ";
cin >> c;
} while(c < "1" || c > "3");
switch(c) {
case "1":
cin >> personObject;
cout << "Entry is: ";
cout << personObject;
pb << personObject;
break;
case "2":
char ch;
pb.seekg(0, ios::beg);
while(!pb.eof()) {
pb.get(ch);
if(!pb.eof())
cout << ch;
}
pb.clear();
cout << endl;
break;
case "3":
pb.close();
return 0;
}
}
}

</source>

==Serialize object Demo==

<source lang="cpp">
#include <iostream>
#include <fstream>
#include <cstring>
using namespace std;
#define SIZE 40
class Product {
char item[SIZE];
int onhand;
double cost;
public:
Product(char *i, int o, double c)
{
strcpy(item, i);
onhand = o;
cost = c;
}
void store(fstream &stream);
void retrieve(fstream &stream);
friend ostream &operator<<(ostream &stream, Product ob);
friend istream &operator>>(istream &stream, Product &ob);
};
ostream &operator<<(ostream &stream, Product ob)
{
stream << ob.item << ": " << ob.onhand;
stream << " on hand at $" << ob.cost << "\n";
return stream;
}
istream &operator>>(istream &stream, Product &ob)
{
cout << "Enter item name: ";
stream >> ob.item;
cout << "Enter number on hand: ";
stream >> ob.onhand;
cout << "Enter cost: ";
stream >> ob.cost;
return stream;
}
void Product::store(fstream &stream)
{
stream.write(item, SIZE);
stream.write((char *) &onhand, sizeof(int));
stream.write((char *) &cost, sizeof(double));
}
void Product::retrieve(fstream &stream)
{
stream.read(item, SIZE);
stream.read((char *) &onhand, sizeof(int));
stream.read((char *) &cost, sizeof(double));
}
int main()
{
fstream fileStream("fileStream", ios::out | ios::binary);
int i;
Product productObject1("p", 12, 4.95);
Product productObject2("h", 5, 9.45);
Product productObject3("w", 22, 13.90);
Product productObject4("", 0, 0.0);
if(!fileStream) {
cout << "Cannot open file for output.\n";
return 1;
}
// write to file
productObject1.store(fileStream);
productObject2.store(fileStream);
productObject3.store(fileStream);
fileStream.close();
// open for input
fileStream.open("fileStream", ios::in | ios::binary);
if(!fileStream) {
cout << "Cannot open file for input.\n";
return 1;
}
do {
cout << "Record # (-1 to quit): ";
cin >> i;
if(i == -1)
break;
fileStream.seekg(i*(SIZE+sizeof(int)+sizeof(double)), ios::beg);
productObject4.retrieve(fileStream);
cout << productObject4;
} while(fileStream.good());
fileStream.close();
return 0;
}

</source>

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