BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Using MethodAddress for dynamic execution          BorlandTalk.com Forum Index -> Delphi VCL Components Using View previous topic :: View next topic   Author Message Pete Gajria Guest Posted: Tue Oct 28, 2003 3:15 pm    Post subject: Using MethodAddress for dynamic execution Hi, I'm trying to exec published procedures dynamically for a given component e.g on a form i have a TEdit & a button The problem is methodaddress always returns nil so obviously ive overlooked something heres the code below any help would be really appreciated thanks pete type TExecute = procedure of object; TForm1 = class(TForm) ....etc etc public { Public declarations } procedure ProcessText(Instance: TObject; Name: string); implementation uses TypInfo; procedure TForm1.Button1Click(Sender: TObject); begin ProcessText(Edit1, 'Clear'); end; procedure TForm1.ProcessText(Instance: TObject; Name: string); Var Routine: TMethod; Execute: TExecute; Begin Routine.Data := Pointer(Instance); Routine.Code := Instance.ClassType.MethodAddress(Name); if Routine.Code = nil then begin showmessage('failed'); Exit; end; Execute := TExecute(Routine); Execute; end; Back to top Marc Rohloff Guest Posted: Tue Oct 28, 2003 5:21 pm    Post subject: Re: Using MethodAddress for dynamic execution On Tue, 28 Oct 2003 07:15:17 -0800, Pete Gajria<pete.gajria (AT) clarksecurity (DOT) com> said ... Quote: Hi, I'm trying to exec published procedures dynamically for a given component e.g on a form i have a TEdit & a button The problem is methodaddress always returns nil so obviously ive overlooked something Where do you define the method you want to call dynamically? Marc Back to top Pete Gajria Guest Posted: Tue Oct 28, 2003 6:31 pm    Post subject: Re: Using MethodAddress for dynamic execution Here procedure TForm1.Button1Click(Sender: TObject); begin ProcessText(Edit1, 'Clear'); <---- Object, Method end; btw i reposted my earlier message in the obj pascal newsgroup since i thought this was the wrong group to post to my earlier msg also contains a complete code sample ive googled & come up with similar examples so i dont understand why methodaddress is returning nil regards, pete On Tue, 28 Oct 2003 12:21:19 -0500, Marc Rohloff rohloff at bigfoot dot com Quote: On Tue, 28 Oct 2003 07:15:17 -0800, Pete Gajria<pete.gajria (AT) clarksecurity (DOT) com> said ... Hi, I'm trying to exec published procedures dynamically for a given component e.g on a form i have a TEdit & a button The problem is methodaddress always returns nil so obviously ive overlooked something Where do you define the method you want to call dynamically? Marc Back to top Peter Below (TeamB) Guest Posted: Tue Oct 28, 2003 8:13 pm    Post subject: Re: Using MethodAddress for dynamic execution In article <oprxrdzrvzajys4f (AT) newsgroups (DOT) borland.com>, Pete Gajria wrote: Quote: Hi, I'm trying to exec published procedures dynamically for a given component e.g on a form i have a TEdit & a button The problem is methodaddress always returns nil so obviously ive overlooked something heres the code below any help would be really appreciated thanks pete type TExecute = procedure of object; TForm1 = class(TForm) ....etc etc public { Public declarations } procedure ProcessText(Instance: TObject; Name: string); implementation uses TypInfo; procedure TForm1.Button1Click(Sender: TObject); begin ProcessText(Edit1, 'Clear'); Clear is not a published method. In fact no VCL control I'm aware of declares any published methods, so this kind of scheme only works with your own classes, including forms, frames, datamodules you create in the designer. -- Peter Below (TeamB) Use the newsgroup archives : http://www.mers.com/searchsite.html http://www.tamaracka.com/search.htm http://groups.google.com http://www.prolix.be Back to top Pete Gajria Guest Posted: Tue Oct 28, 2003 8:18 pm    Post subject: Re: Using MethodAddress for dynamic execution Hi Peter, Heres what i found in the help for TEdit Deletes all text from the edit control. procedure Clear; virtual; Ok so if I understand you correctly the above method is simply a public class member & not published... so how would one go about accessing a public method in a dynamic manner like i'm attempting to do regards, pete Quote: Clear is not a published method. In fact no VCL control I'm aware of declares any published methods, so this kind of scheme only works with your own classes, including forms, frames, datamodules you create in the designer. -- Peter Below (TeamB) Use the newsgroup archives : http://www.mers.com/searchsite.html http://www.tamaracka.com/search.htm http://groups.google.com http://www.prolix.be Back to top David Knaack Guest Posted: Tue Oct 28, 2003 8:48 pm    Post subject: Re: Using MethodAddress for dynamic execution Pete Gajria wrote: Quote: Ok so if I understand you correctly the above method is simply a public class member & not published... so how would one go about accessing a public method in a dynamic manner like i'm attempting to do You might consider using either Delphi Web Script (don't be mislead by the 'web' in the name), or Innerfuse Pascal Script. DWS will require you to wrap all the functions you wish to call, IFS can build the calls dynamicly given the function prototype. There are some extensions to DWS written by Mark Ericksen that make the process of wrapping classes for use with DWS much easier. Either of these would let you call methods with parameters. The JCLDebugIDE might also have some possabilities. DK Back to top Pete Gajria Guest Posted: Tue Oct 28, 2003 9:05 pm    Post subject: Re: Using MethodAddress for dynamic execution The problem is at runtime i may not know the class of the object being passed so basically i wanted to check if it had implemented a particular method & if so exec it i dont think innerfuse or dws would work in such a situation but i will look at them all the same On Tue, 28 Oct 2003 14:48:28 -0600, David Knaack <davidknaack (AT) cox (DOT) net> wrote: Quote: Pete Gajria wrote: Ok so if I understand you correctly the above method is simply a public class member & not published... so how would one go about accessing a public method in a dynamic manner like i'm attempting to do You might consider using either Delphi Web Script (don't be mislead by the 'web' in the name), or Innerfuse Pascal Script. DWS will require you to wrap all the functions you wish to call, IFS can build the calls dynamicly given the function prototype. There are some extensions to DWS written by Mark Ericksen that make the process of wrapping classes for use with DWS much easier. Either of these would let you call methods with parameters. The JCLDebugIDE might also have some possabilities. DK Back to top Marc Rohloff Guest Posted: Tue Oct 28, 2003 9:31 pm    Post subject: Re: Using MethodAddress for dynamic execution On Tue, 28 Oct 2003 13:05:54 -0800, Pete Gajria<pete.gajria (AT) clarksecurity (DOT) com> said ... Quote: The problem is at runtime i may not know the class of the object being passed so basically i wanted to check if it had implemented a particular method & if so exec it i dont think innerfuse or dws would work in such a situation but i will look at them all the same This is not possible. Marc Back to top Marc Rohloff Guest Posted: Tue Oct 28, 2003 11:28 pm    Post subject: Re: Using MethodAddress for dynamic execution Quote: This is not possible. OK maybe I shouldn't say that. There are two other ways you could go. 1) If you use packages for all your controls then you can go through the packages' exports sections and look for the address of the procedure. 2) You can add Map information to your file and use that to do the look up. In either case you will have to go up the hierarchy of classes and check them all (For example TEdit does not supply the clear method, TCustomEdit does) Also for both alternatives you would want to look at something like the JCL Debug routines which show you how to access this information and provide a lot of utilities to do so. Marc Back to top Pete Gajria Guest Posted: Tue Oct 28, 2003 11:38 pm    Post subject: Re: Using MethodAddress for dynamic execution so the point being theres no easy way to get at the public members of a class dynamically unless they are published ? also theres no way to check if a class implements a proc ? whether that proc is published or public "Marc Rohloff" <marc rohloff at bigfoot dot com> wrote Quote: This is not possible. OK maybe I shouldn't say that. There are two other ways you could go. 1) If you use packages for all your controls then you can go through the packages' exports sections and look for the address of the procedure. 2) You can add Map information to your file and use that to do the look up. In either case you will have to go up the hierarchy of classes and check them all (For example TEdit does not supply the clear method, TCustomEdit does) Also for both alternatives you would want to look at something like the JCL Debug routines which show you how to access this information and provide a lot of utilities to do so. Marc Back to top Robert Cerny Guest Posted: Wed Oct 29, 2003 11:40 am    Post subject: Re: Using MethodAddress for dynamic execution A pascal interpreter like the mentioned would do the job. MethodAddress looks up published members. Interpreter has registered public methods, so it can execute them by name, IOW it can look up if there's a registered method for class of particular object. -- Robert Cerny DelphiShaman "Pete Gajria" <pete.gajria (AT) clarksecurity (DOT) com> wrote Quote: The problem is at runtime i may not know the class of the object being passed so basically i wanted to check if it had implemented a particular method & if so exec it i dont think innerfuse or dws would work in such a situation but i will look at them all the same Back to top Marc Rohloff Guest Posted: Wed Oct 29, 2003 12:23 pm    Post subject: Re: Using MethodAddress for dynamic execution On Tue, 28 Oct 2003 15:38:20 -0800, Pete Gajria<pete (AT) gajrias (DOT) org> said .... Quote: so the point being theres no easy way to get at the public members of a class dynamically unless they are published ? Well the two other options I mentioned can access public members too. In fact the package method will let you access the protected members and the debug map will let you access even private members. The package exports method also gives you an indication of the parameters. Quote: also theres no way to check if a class implements a proc ? whether that proc is published or public. If the class has RTTI enabled and publishes a method then yes GetMethodAddress will tell you this. 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