What is IDispatch interface?

What is IDispatch interface?

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. It also provides the information necessary to invoke these properties and methods.

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 COM programming?

Component Object Model (COM) is a binary-interface standard for software components introduced by Microsoft in 1993. It is used to enable inter-process communication object creation in a large range of programming languages.

How does query interface work?

Because the object implements QueryInterface, it has the ability to accept or reject the request. If the object accepts the client’s request, QueryInterface returns a new pointer to the requested interface to the client. Through that interface pointer, the client has access to the methods of that interface.

What is the purpose of query interface?

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.

What is OLE used for?

OLE is a mechanism that allows users to create and edit documents containing items or “objects” created by multiple applications. OLE was originally an acronym for Object Linking and Embedding. However, it is now referred to as OLE.

Why do we need 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.

What is a COM+ application?

A COM+ application is the primary unit of administration and security for Component Services and consists of a group of COM components that generally perform related functions. These components further consist of interfaces and methods, as shown in the following illustration.

Is COM still used?

COM is still in wide use today, although it’s considered an older cousin to the . NET Framework. Many technologies you rely on, and use with PowerShell, are still based on COM.

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 are the query interface methods?

org.hibernate Interface Query

Method Summary
int executeUpdate() Execute the update or delete statement.
String[] getReturnAliases() Return the HQL select clause aliases (if any)
Type[] getReturnTypes() Return the Hibernate types of the query result set.
Iterator iterate() Return the query results as an Iterator.

What is the use of IDispatch?

It provides a late-binding mechanism to access and retrieve information about an object’s methods and properties. Previously, server developers had to implement both the IDispatch and IAccessible interfaces for their accessible objects; that is, they had to provide a dual interface.

Why do we need IDispatch for dual interfaces?

The explanation for this riddle is that in the case of dual interfaces, Visual Basic lets you access methods and properties that are not in the type library. For these unknown elements, Visual Basic has no choice but to resort to the IDispatch interface—even if the object was not declared As Object. ‘ Set up the connection (not using IDispatch).

How do I use IDispatch in ActiveX?

ActiveX or OLE objects can implement the IDispatch interface for access by ActiveX clients, such as Visual Basic. The object’s properties and methods can be accessed using IDispatch::GetIDsOfNames and IDispatch::Invoke.

How to get the type of an object using IDispatch?

Here’s how you do it. The IDispatch::GetTypeInfoCount function is called by the client to determine whether type information is available for the object. If the object provides type information, the integer pointed to by pCountTypeInfo should be set to 1; otherwise, it should be set to 0.