Working with simple properties

We will use the Boolean property to describe how simple properties are used.

This property is described in the type library as follows: 

interface IMyObject : IUnknown {
...
[propget]
HRESULT MyProperty([out, retval]VARIANT_BOOL* result);

[propput]
HRESULT MyProperty([in]VARIANT_BOOL value);
...
};

In Visual Basic this property is handled as follows:

If MyObject.MyProperty <> True Then
   MyObject.MyProperty = True
End If

In C++ there are two ways to use this property. These methods have get_ and put_ prefixes. C++ code sample:

IMyObject* pMyObject;
...
VARIANT_BOOL res;
pMyObject->get_MyProperty(&res);
if( res != VARIANT_TRUE )
   pMyObject->put_MyProperty(VARIANT_TRUE);

 Native COM support makes this procedure simpler. Code sample:

IMyObjectPtr pMyObject;
 ...
if(pMyObject->MyProperty != VARIANT_TRUE) pMyObject->MyProperty = VARIANT_TRUE;

 If the type library only defines the "get" method for a property, this property is called read-only. Its value cannot be changed by the user and it may only be accessed for reading.

Working with string properties is described in the next article.

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