C++ Tutorial/vector/object vector — различия между версиями
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Версия 14:21, 25 мая 2010
Содержание
Call member function for each element in vector
/* The following code example is taken from the book
* "The C++ Standard Library - A Tutorial and Reference"
* by Nicolai M. Josuttis, Addison-Wesley, 1999
*
* (C) Copyright Nicolai M. Josuttis 1999.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/
//#define mem_fun1 mem_fun
#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <functional>
class Person {
private:
std::string name;
public:
//...
void print () const {
std::cout << name << std::endl;
}
void printWithPrefix (std::string prefix) const {
std::cout << prefix << name << std::endl;
}
};
void foo (const std::vector<Person>& coll)
{
using std::for_each;
using std::bind2nd;
using std::mem_fun_ref;
// call member function print() for each element
for_each (coll.begin(), coll.end(), mem_fun_ref(&Person::print));
// call member function printWithPrefix() for each element
// - "person: " is passed as an argument to the member function
for_each (coll.begin(), coll.end(),bind2nd(mem_fun_ref(&Person::printWithPrefix),"person: "));
}
void ptrfoo (const std::vector<Person*>& coll)
// ^^^ pointer !
{
using std::for_each;
using std::bind2nd;
using std::mem_fun;
// call member function print() for each referred object
for_each (coll.begin(), coll.end(),
mem_fun(&Person::print));
// call member function printWithPrefix() for each referred object
// - "person: " is passed as an argument to the member function
for_each (coll.begin(), coll.end(),bind2nd(mem_fun(&Person::printWithPrefix),"person: "));
}
int main()
{
std::vector<Person> coll(5);
foo(coll);
std::vector<Person*> coll2;
coll2.push_back(new Person);
ptrfoo(coll2);
}person: person: person: person: person: person:
Call the virtual function from classes stored in a vector
#include <iostream>
#include <string>
#include <vector>
using namespace std;
class Employee {
string firstName, lastName;
public:
Employee(string fnam, string lnam) {
firstName = fnam;
lastName = lnam;
}
virtual void print() const {
cout << firstName << " " << lastName << " ";
}
virtual ~Employee(){}
};
class Manager : public Employee {
short level;
public:
Manager(string fnam, string lnam, short lvl)
: Employee(fnam, lnam), level(lvl) {}
void print() const {
Employee::print();
cout << " works at level: " << level;
}
~Manager(){}
};
int main()
{
vector<Employee*> empList;
Employee* e1 = new Employee("A", "B");
Employee* e2 = new Employee("C", "D");
Employee* e3 = new Manager( "E", "F", 2 );
Employee* e4 = new Manager( "G", "H", 3 );
empList.push_back( e1 );
empList.push_back( e2 );
empList.push_back( e3 );
empList.push_back( e4 );
vector<Employee*>::iterator p = empList.begin();
while ( p < empList.end() ) {
(*p++)->print();
cout << endl;
}
delete e1;
delete e2;
delete e3;
delete e4;
return 0;
}Object vector
#include <vector>
using namespace std;
class Element
{
public:
Element() {}
~Element() {}
};
int main(int argc, char** argv)
{
vector<Element> elementVector;
return (0);
}Store a class object in a vector.
#include <iostream>
#include <vector>
#include <cstdlib>
using namespace std;
class DailyTemp {
int temp;
public:
DailyTemp() { temp = 0; }
DailyTemp(int x) { temp = x; }
DailyTemp &operator=(int x) {
temp = x; return *this;
}
double get_temp() { return temp; }
};
bool operator<(DailyTemp a, DailyTemp b)
{
return a.get_temp() < b.get_temp();
}
bool operator==(DailyTemp a, DailyTemp b)
{
return a.get_temp() == b.get_temp();
}
int main()
{
vector<DailyTemp> v;
unsigned int i;
for(i=0; i<7; i++)
v.push_back(DailyTemp(60 + rand()%30));
cout << "Fahrenheit temperatures:\n";
for(i=0; i<v.size(); i++)
cout << v[i].get_temp() << " ";
cout << endl;
// convert from Fahrenheit to Centigrade
for(i=0; i<v.size(); i++)
v[i] = (int)(v[i].get_temp()-32) * 5/9 ;
cout << "Centigrade temperatures:\n";
for(i=0; i<v.size(); i++)
cout << v[i].get_temp() << " ";
return 0;
}Use vector as an array for user-defined object
#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
class MyClass {
int p;
public:
MyClass() { p = 42; }
MyClass( int q ) { p = q; }
int getp() const { return p; }
void changeState( int pp ) { p = pp; }
};
bool operator<( const MyClass& x1, const MyClass& x2 ) {
return x1.getp() < x2.getp();
}
bool operator==( const MyClass& x1, const MyClass& x2 ) {
return x1.getp() == x2.getp();
}
void print( vector<MyClass> );
int main()
{
vector<MyClass> vec;
MyClass x1( 2 );
MyClass x2( 3 );
MyClass x3( 5 );
vec.push_back( x1 );
vec.push_back( x3 );
vec.push_back( x2 );
print( vec );
x2.changeState( 1000 );
print( vec);
//vector elements initialized by MyClass"s no-arg constructor:
vector<MyClass> vec_2( 5 );
print( vec_2 );
vec_2.resize( 7 );
print( vec_2 );
//uninitialized increase in the vector capacity:
vec_2.reserve( 10 );
cout << vec_2.capacity() << endl;
print ( vec_2 );
cout << vec_2[ 8 ].getp() << endl;
vec_2[0] = MyClass(12);
vec_2[1] = MyClass(36);
vec_2[2] = MyClass(3);
vec_2[3] = MyClass(56);
vec_2[4] = MyClass(2);
sort( vec_2.begin(), vec_2.end() );
print( vec_2 );
vec_2.clear();
print( vec_2 );
cout << vec_2.capacity() << endl;
return 0;
}
void print( vector<MyClass> v ) {
cout << "\nvector size is: " << v.size() << endl;
vector<MyClass>::iterator p = v.begin();
while ( p != v.end() )
cout << (*p++).getp() << " ";
cout << endl << endl;
}Use vector to store the calsses in a hiearchy
#include <iostream>
#include <string>
#include <vector>
using namespace std;
class Person {
string firstName, lastName;
public:
Person( string fnam, string lnam ): firstName( fnam ), lastName( lnam ) {}
virtual void print() const { cout << firstName << " " << lastName << " "; }
virtual ~Person(){}
};
class Employee : public Person {
string companyName;
public:
Employee( string fnam, string lnam, string cnam )
: Person( fnam, lnam ), companyName( cnam ) {}
void print() const {
Person::print();
cout << companyName << " ";
}
~Employee(){}
};
class Manager : public Employee {
short level;
public:
Manager( string fnam, string lnam, string cnam, short lvl )
: Employee( fnam, lnam, cnam ), level( lvl ) {}
void print() const {
Employee::print();
cout << level;
}
~Manager(){}
};
int main()
{
vector<Employee*> empList;
Employee* e1 = new Employee( "A", "B", "C" );
Employee* e2 = new Employee( "D", "E", "F" );
Employee* m3 = new Manager("G", "H", "I" , 2);
Employee* m4 = new Manager("J", "J", "L", 2);
empList.push_back( e1 );
empList.push_back( e2 );
empList.push_back( m3 );
empList.push_back( m4 );
vector<Employee*>::iterator p = empList.begin();
while ( p < empList. end() ) {
(*p++)->print();
cout << endl;
}
delete e1;
delete e2;
delete m3;
delete m4;
return 0;
}vector with 10 objects
#include <vector>
using namespace std;
class Element
{
public:
Element() {}
~Element() {}
};
int main(int argc, char** argv)
{
vector<Element>* elementVector = new vector<Element>(10);
delete elementVector;
return (0);
}