MQL4参考普通函数 CheckPointer

CheckPointer

The function returns the type of the object pointer.

ENUM_POINTER_TYPE  CheckPointer(
   object* anyobject      // object pointer
   );

Parameters

anyobject

[in] Object pointer.

Return value

Returns a value from the ENUM_POINTER_TYPE enumeration.

Note

An attempt to call an incorrect pointer results in the critical termination of a program. That's why it's necessary to call the CheckPointer function before using a pointer. A pointer can be incorrect in the following cases:

the pointer is equal to NULL;
the object has been deleted using the delete operator.

This function can be used for checking pointer validity. A non-zero value warranties that the pointer can be used for accessing.

Example:

//+------------------------------------------------------------------+
//| Deletes list by deleting its elements                            |
//+------------------------------------------------------------------+
void CMyList::Destroy()
  {
//--- service pointer for working in the loop
   CItem* item;
//--- go through loop and try to delete dynamic pointers
   while(CheckPointer(m_items)!=POINTER_INVALID)
     {
      item=m_items;
      m_items=m_items.Next();
      if(CheckPointer(item)==POINTER_DYNAMIC)
        {
         Print("Dynamyc object ",item.Identifier()," to be deleted");
         delete (item);
        }
      else Print("Non-dynamic object ",item.Identifier()," cannot be deleted");
     }
//---
  }