Does QueryInterface call AddRef?
Because QueryInterface will call AddRef which increases the reference count to the pointer. When there are 0 references to a pointer it is freed for you.
What does QueryInterface do?
Query interface is a type-safe way to achieve a safe downcasting and to allow interfaces to be aggregated to an object. Objects using the query interface must inherit from the Interface base class. This pointer value will be returned null if the node doesn’t support the requested interface.
What is AddRef?
AddRef is used to increment the reference count when a new client is acquiring the object. It returns the new reference count. The object will delete itself during release when the reference-count reaches zero, which means that the caller must never use an interface after calling Release.
When to use AddRef?
You use AddRef to stabilize a copy of an interface pointer. It can also be called when the life of a cloned pointer must extend beyond the lifetime of the original pointer.
What is __ Uuidof?
In a debug build, __uuidof always initializes an object dynamically (at runtime). In a release build, __uuidof can statically (at compile time) initialize an object. For compatibility with previous versions, _uuidof is a synonym for __uuidof unless compiler option /Za (Disable language extensions) is specified.
What is IDispatch interface?
IDispatch is the interface that exposes the OLE Automation protocol. The Automation (IDispatch) interface allows a client application to find out what properties and methods are supported by an object at run-time, i.e. implements the concept of RTTI.
What is QueryInterface C++?
QueryInterface is a mechanism in COM (microsoft’s Component Object Model) for determining if a known component supports a specific interface. You use the current interface pointer (usually IUnknown), and “query” the interface by passing an interface ID to it.
How many unique GUIDs are there?
2128 distinct GUIDs
However, you can try to calculate the chance of creating two GUIDs that are identical and you get the idea: a GUID has 128 bits, hence, there are 2128 distinct GUIDs – much more than there are stars in the known universe.
What is the use of IUnknown interface?
IUnknown interface (unknwn. Enables clients to get pointers to other interfaces on a given object through the QueryInterface method, and manage the existence of the object through the AddRef and Release methods.
What is OLE Automation in VB?
Automation (also called OLE automation) in Visual Basic is the process of controlling one program from another program or external development tool. You can automate any program that contains a Visual Basic object model.
Do GUIDs ever repeat?
No, the computer doesn’t keep track. But no, the chances of a duplicate GUID are so low as to not be relevant. But Guid. NewGuid() does not keep track of the GUIDs generated.
How are GUIDs created?
The general types of GUIDs are: Random: Just use the system’s random-number generator to create a 128-bit number. Time-based: Create a GUID based on the current time. Hardware-based: Make a GUID with certain portions based on hardware features, such as the MAC address of a network card.