The methods and properties of the dispinterface are accessible only via the IDispatch::Invoke method. It's used extensively for scripting. The primary limitation of the IDispatch interface is that it assumes objects are static. Notice that dispinterfaces can support properties as well as methods, while a regular interface supports only methods. The component shown in the following code loads type information from the type library using the LoadRegTypeLib function. In the sample implementation of IDispatchEx::InvokeEx shown here, the code first attempts to delegate the work to the DispInvoke helper function.
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IDispatch is the interface that exposes the OLE Automation protocol. Extending IUnknown, it is It is therefore often a good idea to support both interface types with dual interfaces.
That way The GetIDsOfNames function can be used to get the appropriate DISPID from a property or method name that is in string format. An interface based solely on IDispatch is called a dispinterface.
A dual interface is an IDispatch-based interface that also has v-table entries for . In this case, a string comparison is done with a private member variable named m_newsum.
Server developers must provide the standard Component Object Model (COM) interface IDispatch for their accessible objects.
This method returns a pointer to the type information provided by the object, which can then be used to get the type information for an interface.
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This becomes even more interesting when you realize that the Connection object is not accessed via IDispatch ; it is declared As Connection —not As Object. 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.
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In Figure 38, an IDispatchonly interface is the type in the middle as opposed to a dual interface on the right. The client can read the DISPIDs from the type library.
The member is changed by a reference assignment rather than by a value assignment.
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In addition to the inherited IDispatch methods, IDispatchEx offers seven new methods that support the creation of dynamic objects sometimes called "expando" objects in which methods and properties can be added and removed at run time.
Even so, CreateStdDispatch is a good choice for components that are not hobbled by this restriction. Oleg Oleg k 10 10 gold badges silver badges bronze badges. To get around the one-interface-per-object limitation, some developers have built hacks by which QueryInterface -style semantics can be built into a dispinterface or have suggested identity tricks that allow multiple IDispatch interfaces to be implemented by one object.