Well the best way is to get your idispatch interface directly with its clsid. You may, however, go beyond just handling windows event and create those of your own. Getidsofnames returns an integer id representing the method name. Supporting automation events in delphi delphi programming. The dispid is returned to the client and the structures boolean entry was set to true. The example invokes a method named simple on an object of the class cmyobject. Idispatch getidsofnames is called by a client that has a method name sum, for example and wants to get the dispid associated with that method to call it via idispatch invoke. In my initial proofofconcept version i was manually passing parameters and i was purposefully passing the parameters correctly in reverse order as required by idispatch invoke. Passed in reverse for invoke they are actually the 2nd and 3rd parameters. Mark, without trying it, my first cut would be to set rgvarg to you array of parameters. Internally this method will of course use the typelibrary to find the info. You use different idl attributes depending on whether you are implementing a pure idispatch interface or a dual interface. Idispatchimpl provides a default implementation for the idispatch part of any dual interface on an object.
If you want to call invoke directly, then please show your actual code that is failing. In fact, invoke is the only way to execute a userdefined method through the idispatch interface. Idispatch is the interface that exposes the ole automation protocol. You can store the object reference in a variant variable or use a dispinterface type to write a com server that implements the idispatch interface, simply derive your class from tautoobject in the comobj unit or one of its descendants. Invoke, the method that will be called when any event interface method is triggered. Delphi will call both getidsofnames and invoke for you all you need to do is use a. When using dispinterfaces in delphi, the delphi compiler will emit the proper code that makes the idispatch. How to call delphi code from scripts running in a twebbrowser. And you may even know that its required by comobjects used in autoit with the objcreate function. A lot of you probably heard the name idispatch before. The returned value can be used on subsequent calls to the invoke method. It has two methods that allow pointerless scripting languages to call methods by name, instead of using method pointers.
Sep 28, 2001 cannot pass an idispatch parameter to a method called with idispatch invoke. Also, delphi provides better support for dispinterfaces through the automation object wizard. The idispatch interface exposes a number of methods for automation clients that require latebinding such as scripting languages. This page was last modified on 28 march 2012, at 19. Could someone please give me an example of how to use getidsofnames and invoke to perform the equivalent of, for example. I admit using the delphi way is much more attractive, though.
Just access the members like normal properties, and delphi will call invoke behind the scenes for you. I am using the function idispatch getidsofnames to get ids on methods and their parameters to then pass on to idispatch invoke. A class that acts as an automation controller is definedtmyclasswith a method that takes no arguments and returns an integermymethod. Implement the idispatch interface in comenabled classes that have to act as automation controllers. I can connect and call the members, that is not the issue. Consequently we will use delphis type library editor to create a suitable type library that defines our new interface. Idispatch and cardinal when i run the code the fallowing code. Invoke and the dispparams args, etc have fun, binh ly. But if you want to do that you can use queryinterface to get idispatch pointer but that. Delphi has builtin support for idispatch late binding, so you do not need to call invoke directly. Note that the invocation is done with the help of a dispid dispatch identifier obtained with the getidsofnames. Automation objects supply services to their clients by letting them invoke methods of the interfaces that they expose.
When creating an automation object using the delphi wizard, one of the available. This class implements the methods of idispatch and so saves us from having to do this ourselves. However, tautointfobject needs a type library to work with. Getidsofnames retrieves the numerical id of a method with a given name provided that the object implements another. I have the following code that works fine for a single string parameter but i can not figure out how to send multiple parameters of different types. When you use a com object that implements the idispatch interface, delphi automatically takes care of all the details involved in calling a method dynamically. Note that the invocation is done with the help of a dispid dispatch identifier obtained with the getidsofnames method.
In this selection excerpted from delphi com programming, author eric harmon. I am working on an application, which connects to a com object and calls methods and gets properties from this object etc. Generally, calls to idispatch invoke are preceeded by calls to idispatch getidsofnames. Here is another example for simply calling a property by its dispatch id. Delphi calls the invoke method, using the id returned in step 2.
Delphi programmers take events for granted in their everyday programming tasks. In an ole automation controller, use idispatchinvoke to get and set the values of properties or to call a. Ensure the new interface is derived from idispatch. In essence, idispatch represents a standard vtable with a highly extensible invocation architecture. The real idispatch also has an invoke method next, but we dont need it. Accesing the wmi from object pascal code delphi, oxygene. How to pass safearray to com object through idispatch.
I want to find a way to retrouve the idispatch instance of a giving com object, provifding the i have the id of the object. This file is located in the sourcertlsys directory provided with all versions of delphi that ship with the source to the rtl. Heck its traditional to do that even when youre writing normal delphi applications that you dont want to turn into a giant ball of mud. Yes definitely, the way you are doing is thru idispatch, and is called latebinding and your client is called agnostic client, because you determine functions at runtime using getidsofname and invoke methods thru idispatch table. For example microsoft word manages all its document objects in a collection. A dispinterface is simply a specification for idispatch. As a consequence, it must implement idispatch and therefore iunknown. So if you created an activex control, a button for example and you wanted the click event to be handled by the container of the control and not the control itself you would use connection points.
How does createstddispatch know what method to invoke. Net is handled by the typetotypeinfomarshaler on idispatchinfo. Personsviewmodel is the client of ipersonrepository which is an interface representing the server. An easy way to do this is to derive the new class from tautointfobject. Getidsofnames implements the idispatch interface getidsofnames method. Tobjectdispatchinvoke delphi rad studio code examples. The invoke method will use the found id and will result in a call to the desired method itself. My automation server tfilezapper now has stated that it will provide an implementation for ifilezapper. Even though this is not really an advanced feature, youre going to have to do just a little bit of work in delphi to support events.
If you are using delphis type library editor, simply check the box for the dual flag, and let delphi handle the details for you. For all its methods in the interface i have provided an implementation. Dont edit the one in the codegear folder itself, make sure its a local copy. Obtain type information of idispatchbased com objects from. All that is left in the event sink object is the implementation of idispatch. The important methods are queryinterface, invoke, connect, and disconnect. But, idispatch invoke cannot receive or understand the actual method names or property names of the ms word component. These four methods form the core of automation as it is done by scripting clients. The vtable of a dispinterface is identical to that of idispatch itself. Reflection with idispatchbased com objects codeproject.
Obtain type information of idispatchbased com objects. Cmultidispatchgetidsofnames simply walks the static array calling getidsofnames until successful hence one of the limitations. Variant data types include the basic ones such as integers, strings, characters, and boolean values but also the idispatch interface type. Like a dispinterface, a dual interface supports early binding and late binding. For components that support interfaces, getidsofnames calls this method for the interface supported by the component, passing the specified parameters. Invoke has a fixed compiletime signature that allows it to accept any number of arguments when calling an interface method. This sequence of steps occurs for every method that you call on an object through a variant. Extending iunknown, it is one of the standard interfaces that can be exposed by com objects. To see exactly how delphi calls getidsofnames and invoke, open comobj. This example illustrates the usage of tobjectdispatch.
An interface based solely on idispatch is called a dispinterface. I can get the function to work on methods that do not accept any parameters i. Apr 05, 2009 invoke the client application our program will use the idispatch invoke method to call ms word or any other component methods and properties. But ifilezapper inherites from idispatch, which means i will have to provide an implementation of the idispatch methods as well. Cannot pass an idispatch parameter to a method called with idispatch invoke. In this case, delphi will properly import dispinterface definitions into the servers import module. Calling idispatchgetidsofnames for functions with one or. So far, i havent shown you any automation controllers that fire events. Automation in delphi com programming defining automation. For this example, set this property to ckrunningornew. To write a com server that implements the idispatch interface, simply derive your class from tautoobject in the comobj unit or one of its descendants.
In a real life scenario, you can imagine creating a sqlpersonrepository. The real work of gathering and translating the type information for. Problems using idispatch with activex automation server. Idispatchinvoke passes me disp parameters in reverse order. As you can see, idispatch is a single physical interface that allows less sophisticated clients to get at any number of logical interfaces.
I know i should assign the parameter of type idispatch to a variable declared as a olevariant, but im struggling to extract the data inside. Jan 03, 2010 so, today my mind has been 100 % focused on something that on the surface looks really boring. Idispatchinvoke ole programmers reference winapi reference. Invoke only, without the extra step of calling idispatch. Once it has the dispid, the controller can then call the idispatch method, invoke, to execute the appropriate code property or method, packaging the parameters for the property or method into one of the invoke parameters. Jan 07, 20 preservesig int getdispidref guid riid, ref string name, int namecount, int lcid, out int dispid. I believe you can still access the methods using reflection\ invoke. So it was actually blowing up on my 1st parameter with a type mismatch. A dual interface derives from idispatch and uses only automationcompatible types. But if you want to do that you can use queryinterface to get idispatch pointer but that is not converting you will be getting a new pointer. I am using html in my app and i am trying to capture clicks from the user. Cmultidispatch multiple idispatch interfaces for automation.
The idispatch interface is the basis of all automation. Does anyone have a delphi example of putting together a tdispparams structure with multiple parameters when directly calling idispatch. Any given client application may wish to respond to its own selection of events, however in this case we will respond to both of them. I successfully connect the iwebbrowser2 interface to a dwebbrowserevents2 dispatch event, and my idispatch invoke is called successfully when a user clicks an url. After presenting a couple of examples that use custom interfaces based on type libraries, ill cover the. For example, suppose you create an interface that looks like this.
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