4.6.3 Defining type information for the dispinterface

To define type information for dispinterface, create an instance of the class <disp-type-info>, page 203. We continue the example above by defining type information suitable for <my-dispatch-object>.

If you wanted the my-property slot in the example above to be an OLE Automation property that a controller can read or write, you could define type information like this:

define constant $my-type-info = 
  make(<disp-type-info>, 
       properties: vector(make(<variable-description>,
                               name: "value",
                               documentation: "some value",
                               getter: my-property,
                               setter: my-property-setter)));

The name: option specifies the property name that the controller will see; the Dylan class and function names will not be visible externally.

If you wish, you can deny either read or write access by suppling getter: or setter: values of #f respectively.

The documentation: is optional; it corresponds what is called a "helpstring" in IDL.

Note that a property does not have to correspond to a slot. It simply needs an accessor method specialized on the class. Any number of properties could be specified as elements of the vector. The DISPID values will be assigned automatically; your server does not need to know what they are, because the controller will ask for them by name.

Note that setter: #f simply means that the controller cannot change the value--not that it is necessarily a constant. You can specify a property that really is just a constant value like this:

...
properties: vector(... make(<constant-description>, 
                          name: "pi",
                          value: 3.1416),
                        ...

In this case, the type information contains the complete implementation of the property; no slot or accessor functions are needed.

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OLE, COM, ActiveX and DBMS Reference - 31 MAR 2000