blocks|key|1458781|text|如果有问题的类型没有参数构造函数，请使用new[]|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1458782|Object2*+newArray+=+new+Object2[numberOfObjects];|code-block|syntax|javascript|1458783|当您不再需要数组时，不要忘记调用delete[]：|1458784|delete[]+newArray;|1458785|如果它没有这样的构造函数使用operator+new来分配内存，那么就地调用构造函数：|1458786|//do+for+each+object
::new(+addressOfObject+)+Object2(+parameters+);|1458787|同样，当您不再需要数组时，不要忘记释放它。|1458788|entityMap^0|K|5|0|0|G|8|0|0|E|C|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|Z|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|10|8|@$9|11|A|12|B|C]]|D|@]|E|$]]|$1|M|3|N|5|H|7|13|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|14|8|@$9|15|A|16|B|C]]|D|@]|E|$]]|$1|Q|3|R|5|H|7|17|8|@]|D|@]|E|$I|J]]|$1|S|3|T|5|6|7|18|8|@]|D|@]|E|$]]|$1|U|3|-4|5|6|7|19|8|@]|D|@]|E|$]]]|V|$]]

If the type in question has an no arguments constructor, use <code>new[]</code>:

<pre><code>Object2* newArray = new Object2[numberOfObjects];
</code></pre>

don't forget to call <code>delete[]</code> when you no longer need the array:

<pre><code>delete[] newArray;
</code></pre>

If it doesn't have such a constructor use <code>operator new</code> to allocate memory, then call constructors in-place:

<pre><code>//do for each object
::new( addressOfObject ) Object2( parameters );
</code></pre>

Again, don't forget to deallocate the array when you no longer need it.

blocks|key|1459033|text|假设您的类是Base，并且您有一个单参数构造函数|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1459034|Base+arr[3]+=+{Base(0),+Base(1),+Base(2)}+;|code-block|syntax|javascript|1459035|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Assuming that your class is Base and you have a one argument constructor

<pre><code>Base arr[3] = {Base(0), Base(1), Base(2)} ;
</code></pre>

blocks|key|249473|text|//+allocate+memory
Object2*+objArray+=+static_cast<Object2*>(+::operator+new+(+sizeof+Object2+*+NUM_OF_OBJS+)+);
//+invoke+constuctors
for+(+size_t+i+=+0;+i+<+NUM_OF_OBJS;+i%2B%2B+)
++new+(&objArray[i])+Object2(+/*+initializers+*/+);

//+...+do+some+work

//+invoke+destructors
for+(+size_t+i+=+0;+i+<+NUM_OF_OBJS;+i%2B%2B+)
++objArray[i].~Object2();

//+deallocate+memory
::operator+delete+(+objArray+);|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|249474|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>// allocate memory
Object2* objArray = static_cast&lt;Object2*&gt;( ::operator new ( sizeof Object2 * NUM_OF_OBJS ) );
// invoke constuctors
for ( size_t i = 0; i &lt; NUM_OF_OBJS; i++ )
 new (&amp;objArray[i]) Object2( /* initializers */ );

// ... do some work

// invoke destructors
for ( size_t i = 0; i &lt; NUM_OF_OBJS; i++ )
 objArray[i].~Object2();

// deallocate memory
::operator delete ( objArray );
</code></pre>

blocks|key|1458855|text|Object2+*myArray[42];
for+(int+i+=+0;+i+<+42;+i%2B%2B)
{
++myArray[i]+=+new+Object2(param1,+param2,+...);
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1458856|稍后，您必须遍历数组并逐个释放每个成员：|unstyled|1458857|for+(int+j+=+0;+j+<+42;+j%2B%2B)
{
++delete+myArray[j];
}|1458858|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|L|8|@]|9|@]|A|$]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$B|C]]|$1|I|3|-4|5|F|7|N|8|@]|9|@]|A|$]]]|J|$]]

<pre><code>Object2 *myArray[42];
for (int i = 0; i &lt; 42; i++)
{
 myArray[i] = new Object2(param1, param2, ...);
}
</code></pre>

Later on you will have to walk through the array and deallocate each member individually:

<pre><code>for (int j = 0; j &lt; 42; j++)
{
 delete myArray[j];
}
</code></pre>

blocks|key|2867868|text|使用指向Object2的指针数组：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2867869|std::tr1::shared_ptr<Object2>*+newArray+=+new+shared_ptr<Object2>[numberOfObjects];
for(int+i+=+0;+i+<+numberOfObjects;+i%2B%2B)
{
++++newArray[i]+=+shared_ptr<Object2>(new+Object2(params));
}|code-block|syntax|javascript|2867870|或者，不使用shared_ptr：|2867871|Object2**+newArray+=+new+Object2*[numberOfObjects];
for(int+i+=+0;+i+<+numberOfObjects;+i%2B%2B)
{
++++newArray[i]+=+new+Object2(params);
}|2867872|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Use an array of pointers to Object2:

<pre><code>std::tr1::shared_ptr&lt;Object2&gt;* newArray = new shared_ptr&lt;Object2&gt;[numberOfObjects];
for(int i = 0; i &lt; numberOfObjects; i++)
{
 newArray[i] = shared_ptr&lt;Object2&gt;(new Object2(params));
}
</code></pre>

Or, alternatively, without the use of shared_ptr:

<pre><code>Object2** newArray = new Object2*[numberOfObjects];
for(int i = 0; i &lt; numberOfObjects; i++)
{
 newArray[i] = new Object2(params);
}
</code></pre>

blocks|key|2867916|text|您可以像std::vector一样创建一块原始内存块。然后，在需要的时候，使用placement+new来构造内存中没有默认构造函数的对象。当然，如果你这样做了，你还不如从一开始就使用std::vector。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2867917|entityMap^0|4|B|2K|B|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|M|8|@]|D|@]|E|$]]]|G|$]]

You can do what <code>std::vector</code> does and create a block of raw memory. You then construct your objects which don't have a default constructor in that memory using placement new, as they are required. But of course, if you do that you might as well have used <code>std::vector</code> in the first place.

blocks|key|2867743|text|如果没有可用的默认构造函数，您将需要一个指针数组，然后循环该数组以初始化每个指针。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2867744|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

If no default constructor is available, you will need an array of pointers, and then loop over that array to initialize each of the pointers.

blocks|key|997877|text|一个显而易见的问题是为什么您不想使用STL。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|997878|假设你有一个理由，你会创建一个像Obj+*+op+=+new+Obj[4];这样的对象数组。只需记住用delete+[]+op;去掉它。|offset|length|style|CODE|997879|你不能用一个没有构造函数的不带参数的对象做到这一点。在这种情况下，我认为你能做的最好的就是分配一些内存并使用placement+new。它不像其他方法那样简单。|997880|entityMap^0|0|G|M|1F|D|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|M|8|@$D|N|E|O|F|G]|$D|P|E|Q|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|R|8|@]|9|@]|A|$]]|$1|J|3|-4|5|6|7|S|8|@]|9|@]|A|$]]]|K|$]]

The obvious question is why you don't want to use the STL.

Assuming you have a reason, you would create an array of objects with something like <code>Obj * op = new Obj[4];</code>. Just remember to get rid of it with <code>delete [] op;</code>.

You can't do that with an object with no constructor that doesn't take arguments. In that case, I think the best you could do is allocate some memory and use placement new. It isn't as straightforward as the other methods.

blocks|key|997969|text|如果您确实需要一个非默认可构造类型的数组(连续的对象序列)，并且出于某种原因，您可以使用用户std::vector+(!?)然后你必须使用一个原始的分配函数并放置新的。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|997970|这很难可靠地做到；这应该有助于说明原因。这段代码包括一些针对异常的防御，但很可能不是针对所有故障的健壮性。|997971|const+size_t+required_count+=+100;+//e.g.

//+cast+to+pointer+of+required+type+needed+for+pointer+arithmetic
Object2*+objarray+=+static_cast<Object2*>(operator+new(required_count+*+sizeof(Object2)));

size_t+construction_count+=+0;

try
{
++++while+(construction_count+<+required_count)
++++{
++++++++//+params+could+change+with+index.
++++++++new+(static_cast<void*>(objarray+%2B+construction_count))+Object2(param1,+param2);
++++++++%2B%2Bconstruction_count;
++++}
}
catch+(...)
{
++++while+(construction_count--+!=+0)
++++{
++++++++try
++++++++{
++++++++++++(&objarray[construction_count])->~Object2();
++++++++}
++++++++catch+(...)
++++++++{
++++++++++++//+not+a+lot+we+can+do+here,+log+but+don't+re-throw.
++++++++}
++++}

++++operator+delete(objarray);
++++throw;
}

//+Now+objarray+has+been+allocated+and+pointer+to+an+array+of+required_count+Object2
//+It+cannot+be+de-allocated+via+delete[]+or+delete;+you+must+loop+through
//+calling+destructors+and+then+call+operator+delete+on+the+buffer.|code-block|syntax|javascript|997972|entityMap^0|1A|B|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|R|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|S|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|N|$]]

If you genuinely need an array (contiguous sequence of objects) of a non-default constructible type and for some reason you cannoy user <code>std::vector</code> (!?) then you have to use a raw allocation function and placement new.

This is very hard to do reliably; this should help to show why. This snippet includes some defence against exceptions but is more than likely not robust against all failures.

<pre><code>const size_t required_count = 100; //e.g.

// cast to pointer of required type needed for pointer arithmetic
Object2* objarray = static_cast&lt;Object2*&gt;(operator new(required_count * sizeof(Object2)));

size_t construction_count = 0;

try
{
 while (construction_count &lt; required_count)
 {
 // params could change with index.
 new (static_cast&lt;void*&gt;(objarray + construction_count)) Object2(param1, param2);
 ++construction_count;
 }
}
catch (...)
{
 while (construction_count-- != 0)
 {
 try
 {
 (&amp;objarray[construction_count])-&gt;~Object2();
 }
 catch (...)
 {
 // not a lot we can do here, log but don't re-throw.
 }
 }

 operator delete(objarray);
 throw;
}

// Now objarray has been allocated and pointer to an array of required_count Object2
// It cannot be de-allocated via delete[] or delete; you must loop through
// calling destructors and then call operator delete on the buffer.
</code></pre>

I want to create in C++ an array of Objects without using STL.

How can I do this?

How could I create array of Object2, which has no argumentless constructor (default constructor)?

C++, array of objects without <vector>

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我想在不使用STL的情况下在C++中创建一个对象数组。我该怎么做呢？如何创建没有无参数构造函数(默认构造函数)的Object2数组？

问C++，不带<vector>的对象数组
EN

回答 9

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