в 14:21, 25 мая 2010

2010-05-25T14:21:17Z

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2010-05-25T10:29:26Z

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==Refer to static variable through its class name==

<source lang="cpp">#include <iostream>
using namespace std;

class MyClass {
public:
static int num;
void display() { cout << num << endl; }
};

int MyClass::num; // define num

int main()
{
MyClass a, b;

// Set num through its class name.
MyClass::num = 100;

a.display();
b.display();

// Set num through an object.
a.num = 200;

a.display();
b.display();

return 0;
}</source>
<pre class=codeResult>100
100
200
200</pre>

==static data members==

<source lang="cpp">#include <iostream>

class MyClass
{
public:
MyClass(int age = 1):intValue(age){
InstanceCount++;
}
virtual ~MyClass() {
InstanceCount--;
}
virtual int getValue() {
return intValue;
}
virtual void setValue(int age) {
intValue = age;
}
static int InstanceCount;

private:
int intValue;

};

int MyClass::InstanceCount = 0;

int main()
{
const int count = 5;
MyClass *MyClassHouse[count];
int i;
for (i = 0; i<count; i++)
MyClassHouse[i] = new MyClass(i);

for (i = 0; i<count; i++)
{
std::cout << "There are ";
std::cout << MyClass::InstanceCount;
std::cout << " left!\n";
std::cout << "Deleting the one which is ";
std::cout << MyClassHouse[i]->getValue();
delete MyClassHouse[i];
MyClassHouse[i] = 0;
}
return 0;
}</source>
<pre class=codeResult>There are 5 left!
Deleting the one which is 0There are 4 left!
Deleting the one which is 1There are 3 left!
Deleting the one which is 2There are 2 left!
Deleting the one which is 3There are 1 left!
Deleting the one which is 4</pre>

==Use a static instance variable==

<source lang="cpp">#include <iostream>
using namespace std;

class MyClass {
static int num;
public:
void setI(int i) { num = i; };
void display() { cout << num << " "; }
};

int MyClass::num; // define num

int main()
{
MyClass a, b;

a.display(); // prints 0
b.display(); // prints 0

a.setI(10); // set static num to 10

a.display(); // prints 10
b.display(); // also prints 10

return 0;
}</source>
<pre class=codeResult>0 0 10 10</pre>

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в 14:21, 25 мая 2010

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