ICollectionOnSTLImpl Class

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This class provides methods used by a collection class.

Syntax

template <class T, class CollType, class ItemType, class CopyItem, class EnumType>  
class ICollectionOnSTLImpl : public T```  
  
#### Parameters  
 `T`  
 A COM collection interface.  
  
 `CollType`  
 An STL container class.  
  
 *ItemType*  
 The type of item exposed by the container interface.  
  
 *CopyItem*  
 A [copy policy class](../Topic/ATL%20Copy%20Policy%20Classes.md).  
  
 *EnumType*  
 A [CComEnumOnSTL](../Topic/CComEnumOnSTL%20Class.md)-compatible enumerator class.  
  
## Members  
  
### Public Methods  
  
|Name|Description|  
|----------|-----------------|  
|[ICollectionOnSTLImpl::get__NewEnum](#icollectiononstlimpl__get__newenum)|Returns an enumerator object for the collection.|  
|[ICollectionOnSTLImpl::getcount](#icollectiononstlimpl__get_count)|Returns the number of elements in the collection.|  
|[ICollectionOnSTLImpl::get_Item](#icollectiononstlimpl__get_item)|Returns the requested item from the collection.|  
  
### Public Data Members  
  
|Name|Description|  
|----------|-----------------|  
|[ICollectionOnSTLImpl::m_coll](#icollectiononstlimpl__m_coll)|The collection.|  
  
## Remarks  
 This class provides the implementation for three methods of a collection interface: [getcount](#icollectiononstlimpl__get_count), [get_Item](#icollectiononstlimpl__get_item), and [get__NewEnum](#icollectiononstlimpl__get__newenum).  
  
 To use this class:  
  
-  Define (or borrow) a collection interface that you wish to implement.  
  
-  Derive your class from a specialization of `ICollectionOnSTLImpl` based on this collection interface.  
  
-  Use your derived class to implement any methods from the collection interface not handled by `ICollectionOnSTLImpl`.  
  
> [!NOTE]
>  If the collection interface is a dual interface, derive your class from [IDispatchImpl](../Topic/IDispatchImpl%20Class.md), passing the `ICollectionOnSTLImpl` specialization as the first template parameter if you want ATL to provide the implementation of the `IDispatch` methods.  
  
-  Add items to the [m_coll](#icollectiononstlimpl__m_coll) member to populate the collection.  
  
 For more information and examples, see [ATL Collections and Enumerators](../Topic/ATL%20Collections%20and%20Enumerators.md).  
  
## Inheritance Hierarchy  
 `T`  
  
 `ICollectionOnSTLImpl`  
  
## Requirements  
 **Header:** atlcom.h  
  
##  <a name="icollectiononstlimpl__get_count"></a>  ICollectionOnSTLImpl::getcount  
 This method returns the number of items in the collection.  
  

STDMETHOD(getcount)(long* pcount);

  
### Parameters  
 *pcount*  
 [out] The number of elements in the collection.  
  
### Return Value  
 A standard `HRESULT` value.  
  
##  <a name="icollectiononstlimpl__get_item"></a>  ICollectionOnSTLImpl::get_Item  
 This method returns the specified item from the collection.  
  

STDMETHOD(get_Item)(long Index, ItemType* pvar);

  
### Parameters  
 `Index`  
 [in] The 1-based index of an item in the collection.  
  
 `pvar`  
 [out] The item corresponding to `Index`.  
  
### Return Value  
 A standard `HRESULT` value.  
  
### Remarks  
 The item is obtained by copying the data at the specified position in [m_coll](#icollectiononstlimpl__m_coll) using the copy method of the [copy policy class](../Topic/ATL%20Copy%20Policy%20Classes.md) passed as a template argument in the `ICollectionOnSTLImpl` specialization.  
  
##  <a name="icollectiononstlimpl__get__newenum"></a>  ICollectionOnSTLImpl::get__NewEnum  
 Returns an enumerator object for the collection.  
  

STDMETHOD(get__NewEnum)(IUnknown** ppUnk);

  
### Parameters  
 `ppUnk`  
 [out] The **IUnknown** pointer of a newly created enumerator object.  
  
### Return Value  
 A standard `HRESULT` value.  
  
### Remarks  
 The newly created enumerator maintains an iterator on the original collection, `m_coll`, (so no copy is made) and holds a COM reference on the collection object to ensure that the collection remains alive while there are outstanding enumerators.  
  
##  <a name="icollectiononstlimpl__m_coll"></a>  ICollectionOnSTLImpl::m_coll  
 This member holds the items represented by the collection.  
  

CollType m_coll;

  
## See Also  
 [ATLCollections Sample](../Topic/Visual%20C++%20Samples.md)   
 [Class Overview](../Topic/ATL%20Class%20Overview.md)