विश्लेषण की अनुमति दें।
#include <iostream> // not #include "iostream"
using namespace std; // in this case okay, but never do that in header files
class A
{
public:
void f() { cout<<"f()\n"; }
};
int main()
{
/*
// A a; //this works
A *a = new A(); //this doesn't
a.f(); // "f has not been declared"
*/ // below
// system("pause"); <-- Don't do this. It is non-portable code. I guess your
// teacher told you this?
// Better: In your IDE there is prolly an option somewhere
// to not close the terminal/console-window.
// If you compile on a CLI, it is not needed at all.
}
एक सामान्य सलाह के रूप में:
0) Prefer automatic variables
int a;
MyClass myInstance;
std::vector<int> myIntVector;
1) If you need data sharing on big objects down
the call hierarchy, prefer references:
void foo (std::vector<int> const &input) {...}
void bar() {
std::vector<int> something;
...
foo (something);
}
2) If you need data sharing up the call hierarchy, prefer smart-pointers
that automatically manage deletion and reference counting.
3) If you need an array, use std::vector<> instead in most cases.
std::vector<> is ought to be the one default container.
4) I've yet to find a good reason for blank pointers.
-> Hard to get right exception safe
class Foo {
Foo() : a(new int[512]), b(new int[512]) {}
~Foo() {
delete [] b;
delete [] a;
}
};
-> if the second new[] fails, Foo leaks memory, because the
destructor is never called. Avoid this easily by using
one of the standard containers, like std::vector, or
smart-pointers.
अंगूठे का एक नियम के रूप में: यदि आप अपने दम पर स्मृति का प्रबंधन करने की जरूरत है, वहाँ आम तौर पर एक superiour प्रबंधक या पहले से ही उपलब्ध विकल्प है, एक है कि इस प्रकार आरएआईआई सिद्धांत।
स्रोत
2011-07-01 15:36:10
वह पंक्ति जो "यह नहीं करता" वास्तव में ठीक है, जिससे आपका प्रश्न उलझन में दिख रहा है। – juanchopanza