对不起我的代码错了..这是正确的吗？


< code>


int N = 22;

pointerArray * MyClass;

pointerArray = new MyClass [N];

for（int i = 0; i< N; i ++）

pointerArray [i] - > MyClass（i）;


< / code>

Philipp写道：

抱歉我的代码错了......这是正确的吗？

< code>

int N = 22;
pointerArray * MyClass;


这不是指针数组。它是一个指向数组的指针。

pointerArray = new MyClass [N];


new创建一组N个MyClass类型的对象。

for（int i = 0; i< N; i ++）
pointerArray [i] - > MyClass（i）;

这不好。 MyClass类型已经构建。而你

不能调用构造函数，他们没有名字。你想做什么？


-

Attila aka WW

Philipp写道：

int N = 22;
pointerArray * MyClass;


你的意思是''MyClass * pointerArray;''。为什么不发布实际代码？

pointerArray = new MyClass [N];


这次调用MyClass的默认构造函数N次。

for（int i = 0; i< N; i ++）
pointerArray [i ] - > MyClass（i）;

应该是

for（int i = 0; i< N; ++ i ）pointerArray [i] = MyClass（i）;

或

for（int i = 0; i< N; ++ i）

{

pointerArray [i] .~MyClass（）;

new（& pointerArray [i]）MyClass（i）;

}


如果你分配原始内存而不是对象：

pointerArray = reinterpret_cast< MyClass *>

（new char [N * sizeof（MyClass）]）;


然后你不需要在for循环中

placement new之前调用析构函数。但是，在那个

的情况下你需要：


for（int i = 0; i< N; ++ i）pointerArray [i]。 ~MyClass（）;

delete [] reinterpret_cast< char *> （pointerArray）;


而不仅仅是''delete [] pointerArray;''。


基本上，重点是你可以'在

对象上调用构造函数（因为当它是一个对象时，它已经构造了

）。


我希望这会有所帮助，并且我没有犯过太多错误。

问候，

巴斯特。
>

Hello, a very simple question:
Ok I have a class MyClass with a constructor MyClass(int) (no constructor
without argument defined)

how can I make an array of pointers to objects of that class, calling the
constructor with the index number as argument?

<code>
int N = 22;
pointerArray = new MyClass*[N];
for (int i=0; i< N; i++)
pointerArray[i]->MyClass(i);
</code>

is this correct? does the second line call some default constructor for
MyClass? Any better idea how to do that?

Thanks Phil

Sorry my code was wrong... Is this correct?

<code>

int N = 22;
pointerArray* MyClass;
pointerArray = new MyClass[N];
for (int i=0; i< N; i++)
pointerArray[i]->MyClass(i);

</code>

Philipp wrote:

Sorry my code was wrong... Is this correct?

<code>

int N = 22;
pointerArray* MyClass;
This is not a pointer array. It is a pointer to an array.
pointerArray = new MyClass[N];
new creates an array of N pieces of objects of MyClass type.
for (int i=0; i< N; i++)
pointerArray[i]->MyClass(i);

This is not good. The MyClass types are already constructed. And you
cannot call constructors, they have no name. What do you want to do?

--
Attila aka WW

Philipp wrote:

int N = 22;
pointerArray* MyClass;
You mean ''MyClass * pointerArray;''. Why not post the real code?
pointerArray = new MyClass[N];
This calls the default constructor for MyClass N times.
for (int i=0; i< N; i++)
pointerArray[i]->MyClass(i);

Should be
for (int i = 0; i < N; ++ i) pointerArray [i] = MyClass (i);
or
for (int i = 0; i < N; ++ i)
{
pointerArray [i].~MyClass ();
new (& pointerArray [i]) MyClass (i);
}

If you allocate raw memory instead of objects:
pointerArray = reinterpret_cast <MyClass *>
(new char [N * sizeof (MyClass)]);

then you don''t need the destructor call before the
placement new inside the for loop. However, in that
case you would need:

for (int i = 0; i < N; ++ i) pointerArray [i].~MyClass ();
delete [] reinterpret_cast <char *> (pointerArray);

instead of just ''delete [] pointerArray;''.

Basically, the point is that you can''t call a constructor on an
object (because by the time it is an object, it has already been
constructed).

I hope this helps, and that I haven''t made too many mistakes of my own.
Regards,
Buster.