Delphi idispatch invoke example

Obtain type information of idispatchbased com objects. A class that acts as an automation controller is definedtmyclasswith a method that takes no arguments and returns an integermymethod. Delphi will call both getidsofnames and invoke for you all you need to do is use a. 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. 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.

Cmultidispatch multiple idispatch interfaces for automation. Generally, calls to idispatch invoke are preceeded by calls to idispatch getidsofnames. Consequently we will use delphis type library editor to create a suitable type library that defines our new interface. In the delphi language a variant is a typevariant data type, that is a variable that can assume different data types as its value. Automation in delphi com programming defining automation.

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. Idispatch is the interface that exposes the ole automation protocol. The example invokes a method named simple on an object of the class cmyobject. Delphi programmers take events for granted in their everyday programming tasks. Obtain type information of idispatchbased com objects from. 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 believe you can still access the methods using reflection\ invoke. 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. If you are using delphis type library editor, simply check the box for the dual flag, and let delphi handle the details for you. When creating an automation object using the delphi wizard, one of the available.

How does createstddispatch know what method to invoke. 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. I admit using the delphi way is much more attractive, though. If you want to call invoke directly, then please show your actual code that is failing. A lot of you probably heard the name idispatch before. I successfully connect the iwebbrowser2 interface to a dwebbrowserevents2 dispatch event, and my idispatch invoke is called successfully when a user clicks an url. Extending iunknown, it is one of the standard interfaces that can be exposed by com objects. A dual interface derives from idispatch and uses only automationcompatible types. In this selection excerpted from delphi com programming, author eric harmon. Well the best way is to get your idispatch interface directly with its clsid. 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. In fact, invoke is the only way to execute a userdefined method through the idispatch interface.

Just access the members like normal properties, and delphi will call invoke behind the scenes for you. Personsviewmodel is the client of ipersonrepository which is an interface representing the server. A dispinterface is simply a specification for idispatch. As you can see, idispatch is a single physical interface that allows less sophisticated clients to get at any number of logical interfaces. But if you want to do that you can use queryinterface to get idispatch pointer but that. Does anyone have a delphi example of putting together a tdispparams structure with multiple parameters when directly calling idispatch. It has two methods that allow pointerless scripting languages to call methods by name, instead of using method pointers.

So it was actually blowing up on my 1st parameter with a type mismatch. Variant data types include the basic ones such as integers, strings, characters, and boolean values but also the idispatch interface type. After presenting a couple of examples that use custom interfaces based on type libraries, ill cover the. This sequence of steps occurs for every method that you call on an object through a variant. Mark, without trying it, my first cut would be to set rgvarg to you array of parameters. In a real life scenario, you can imagine creating a sqlpersonrepository. These four methods form the core of automation as it is done by scripting clients. Invoke only, without the extra step of calling idispatch.

Calling idispatchgetidsofnames for functions with one or. Getidsofnames returns an integer id representing the method name. Idispatchinvoke passes me disp parameters in reverse. Cmultidispatchgetidsofnames simply walks the static array calling getidsofnames until successful hence one of the limitations. And you may even know that its required by comobjects used in autoit with the objcreate function. An interface based solely on idispatch is called a dispinterface. As a consequence, it must implement idispatch and therefore iunknown. This example illustrates the usage of tobjectdispatch. So far, i havent shown you any automation controllers that fire events. But, idispatch invoke cannot receive or understand the actual method names or property names of the ms word component. Dont edit the one in the codegear folder itself, make sure its a local copy. This class implements the methods of idispatch and so saves us from having to do this ourselves. The dispid is returned to the client and the structures boolean entry was set to true. I can connect and call the members, that is not the issue.

Automation objects supply services to their clients by letting them invoke methods of the interfaces that they expose. Problems using idispatch with activex automation server. Accesing the wmi from object pascal code delphi, oxygene. The invoke method will use the found id and will result in a call to the desired method itself. In essence, idispatch represents a standard vtable with a highly extensible invocation architecture. Note that the invocation is done with the help of a dispid dispatch identifier obtained with the getidsofnames. Note that the invocation is done with the help of a dispid dispatch identifier obtained with the getidsofnames method. To see exactly how delphi calls getidsofnames and invoke, open comobj. You use different idl attributes depending on whether you are implementing a pure idispatch interface or a dual interface. 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. Ensure the new interface is derived from idispatch. Net is handled by the typetotypeinfomarshaler on idispatchinfo. Could someone please give me an example of how to use getidsofnames and invoke to perform the equivalent of, for example.

My automation server tfilezapper now has stated that it will provide an implementation for ifilezapper. Idispatchinvoke ole programmers reference winapi reference. For this example, set this property to ckrunningornew. In an ole automation controller, use idispatchinvoke to get and set the values of properties or to call a. Passed in reverse for invoke they are actually the 2nd and 3rd parameters. The returned value can be used on subsequent calls to the invoke method. When using dispinterfaces in delphi, the delphi compiler will emit the proper code that makes the idispatch. The vtable of a dispinterface is identical to that of idispatch itself. How to pass safearray to com object through idispatch. Invoke and the dispparams args, etc have fun, binh ly. However, tautointfobject needs a type library to work with. For example microsoft word manages all its document objects in a collection.

Idispatch and cardinal when i run the code the fallowing code. This parameter contains a fingerprint template which is referenced as an object in vb. Reflection with idispatchbased com objects codeproject. 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. This page was last modified on 28 march 2012, at 19.

How to call delphi code from scripts running in a twebbrowser. For example, suppose you create an interface that looks like this. Delphi has builtin support for idispatch late binding, so you do not need to call invoke directly. 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. Supporting automation events in delphi delphi programming. Internally this method will of course use the typelibrary to find the info. I am working on an application, which connects to a com object and calls methods and gets properties from this object etc. An easy way to do this is to derive the new class from tautointfobject. You may, however, go beyond just handling windows event and create those of your own. I am using the function idispatch getidsofnames to get ids on methods and their parameters to then pass on to idispatch invoke. You can use a variant to store a reference to an automation object.

Also, delphi provides better support for dispinterfaces through the automation object wizard. In this case, delphi will properly import dispinterface definitions into the servers import module. 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. Invoke, the method that will be called when any event interface method is triggered. Here is another example for simply calling a property by its dispatch id. I am using html in my app and i am trying to capture clicks from the user. Delphi calls the invoke method, using the id returned in step 2. Getidsofnames retrieves the numerical id of a method with a given name provided that the object implements another. This file is located in the sourcertlsys directory provided with all versions of delphi that ship with the source to the rtl. 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. The idispatch interface exposes a number of methods for automation clients that require latebinding such as scripting languages. Cannot pass an idispatch parameter to a method called with idispatch invoke. For components that support interfaces, getidsofnames calls this method for the interface supported by the component, passing the specified parameters. Jan 03, 2010 so, today my mind has been 100 % focused on something that on the surface looks really boring.

Sep 28, 2001 cannot pass an idispatch parameter to a method called with idispatch invoke. Invoke has a fixed compiletime signature that allows it to accept any number of arguments when calling an interface method. 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. For all its methods in the interface i have provided an implementation. Like a dispinterface, a dual interface supports early binding and late binding. The real idispatch also has an invoke method next, but we dont need it. All that is left in the event sink object is the implementation of idispatch. 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.

The important methods are queryinterface, invoke, connect, and disconnect. I successfully connect the iwebbrowser2 interface to a dwebbrowserevents2 dispatch event, and my idispatchinvoke is called successfully when a user clicks an url. 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. The real work of gathering and translating the type information for.

Jan 07, 20 preservesig int getdispidref guid riid, ref string name, int namecount, int lcid, out int dispid. Idispatchimpl provides a default implementation for the idispatch part of any dual interface on an object. Return any values from methods using a parameter that has the out,retval modifier. I can get the function to work on methods that do not accept any parameters i.

Tobjectdispatchinvoke delphi rad studio code examples. The idispatch interface is the basis of all automation. Getidsofnames implements the idispatch interface getidsofnames method. I believe you can still access the methods using reflection\invoke. But ifilezapper inherites from idispatch, which means i will have to provide an implementation of the idispatch methods as well. 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.