This first tutorial describes creating a COM component from a COM definition file that is either an IDL file or a Type Library. The tutorial focuses on creating an in-process (DLL) component, called
StringManipulator. The component exposes one interface
IString that includes the functions
ReplaceSubstring and
PruneAll corresponding respectively to the features
replace_substring and
prune_all of the class
STRING from the EiffelBase library.
IString also exposes the property
String which represents the manipulated string. The property can be set or read.
Step by step instructions
- In Project, in the Current project input field, type in string_manipulator_server and press enter.
- In Project Type, choose Create a new COM component.
- In Component Information, click the browse button (the button with ...) and open the file $ISE_EIFFEL\examples\com\wizard\string_manipulator\string_manipulator.idl where $ISE_EIFFEL represents the path to the EiffelStudio installation directory.
- Make sure Generate and use marshaller DLL is not checked.
- Click Next.
- In Component Type, choose In-process (*.dll).
- In Generation Options, click the browse button and select the directory where the project should be created (later referenced as destination folder). Choose $ISE_EIFFEL\examples\com\wizard\string_manipulator\generated\component where $ISE_EIFFEL represents the path to the EiffelStudio directory.
- Make sure both Compile C code and Compile Eiffel code are checked.
- Make sure Clean destination folder prior to generation is selected.
- Click Generate.
- Wait until the wizard is done.
First look at the generated code
At the end of the processing the EiffelStudio button becomes enabled. Click on it. This will automatically start EiffelStudio with the generated project so you can more easily navigate through the created Eiffel classes. You can save the processing output by clicking the Save button.
The deferred class STRING_MANIPULATOR_COCLASS represents the component and exposes all its functionality. It inherits from ISTRING_INTERFACE which corresponds to the IString interface and has one heir STRING_MANIPULATOR_COCLASS_IMP which implements all the deferred features. The default implementation in the heir is empty.
Implementing the component
To do something more interesting than merely returning an error to the client edit the implementation of the
STRING_MANIPULATOR_COCLASS_IMP class. There is an implementation of the class in
$ISE_EIFFEL\examples\com\wizard\string_manipulator\server\. Copy this file over to
$ISE_EIFFEL\examples\com\wizard\string_manipulator\generated\component\server\component and freeze the project. Voila!, you have your first EiffelCOM component up and running.
Running the component
The component needs to be registered prior to being loaded. Register an out-of-process component using the following syntax:
system_name.exe -Regserver
where
system_name is the name of the component executable file. Register an in-process component using the
regsvr32 utility using the following syntax:
regsvr32 system_name.dll
where
system_name is the name of the dll (e.g. string_manipulator). So to register the
StringManipulator component, run:
cd $ISE_EIFFEL\examples\com\wizard\string_manipulator\generated\component\server\EIFGENs\default\W_code
regsvr32 string_manipulator.dll
Once registered, follow the steps described in
Accessing a COM component to build the component's client.
See Also
Creating a new component from an Eiffel Project
Accessing a COM component.