BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Find an Instance of a form          BorlandTalk.com Forum Index -> C++ Builder (VCL Components Usage) View previous topic :: View next topic   Author Message Jack Mills Guest Posted: Tue Jun 22, 2004 12:24 pm    Post subject: Find an Instance of a form How do I find out if an instance of a form exists? & if it does show it rather than create another new one! I presume it involves "this" & "Owner", but my trial & error attempts are not working out. I have this on a form, this form is not a MDIForm. The TEM_DetailForm style, is set to MDIChild. void __fastcall TEditorChildDG::Edit1Click(TObject *Sender, int LVIndex) { TEM_DetailForm *EM_Detail; EM_Detail = new TEM_DetailForm(this); EM_Detail->Query1->DatabaseName = Query1->DatabaseName; EM_Detail->Query1->Tag = LVIndex; ; EM_Detail->Caption = Caption; EM_Detail->Show(); } I want to insert before that code, in English If TEM_DetailForm that I created exists & its Query1->Tag = LVIndex Show it else create it as above. Thanks for any help Jack Back to top Andrue Cope [TeamB] Guest Posted: Tue Jun 22, 2004 1:00 pm    Post subject: Re: Find an Instance of a form Jack Mills wrote: Quote: How do I find out if an instance of a form exists? The simplest method is to have the form's constructor set a global flag to indicate that it exists. In point of fact the IDE gives you such a flag. Each form has an instance variable at the top. In this case it should be declared as: TEM_DetailForm * EM_DetailForm; so: void __fastcall TEditorChildDG::Edit1Click(TObject *Sender, int LVIndex) { if( !EM_DetailForm ) EM_DetailForm = new TEM_DetailForm(this); EM_DetailForm->Query1->DatabaseName = Query1->DatabaseName; // etc... } Then in the destructor or OnFormDestroy handler add: EM_Detail=NULL; Checking the tag is a bit more complicated if you can have multiple detail forms visable with different tags. For that you'd need to declare your own global array of form pointers or std::vector. Then you iterate through that list checking for a details form with the tag set. Each form constructor would add its 'this' pointer to the array and the destructor would remove it. -- Andrue Cope [TeamB] [Bicester, Uk] http://info.borland.com/newsgroups/guide.html Back to top Andrue Cope [TeamB] Guest Posted: Tue Jun 22, 2004 1:03 pm    Post subject: Re: Find an Instance of a form Andrue Cope [TeamB] wrote: Quote: Then in the destructor or OnFormDestroy handler add: EM_Detail=NULL; Oops I forgot to add that you should ensure the variable is set to NULL at program start as well. Change: TEM_DetailForm * EM_DetailForm; to TEM_DetailForm * EM_DetailForm=NULL; -- Andrue Cope [TeamB] [Bicester, Uk] http://info.borland.com/newsgroups/guide.html Back to top Jack Mills Guest Posted: Tue Jun 22, 2004 1:27 pm    Post subject: Re: Find an Instance of a form Thanks Andrue Quote: Checking the tag is a bit more complicated if you can have multiple detail forms visible with different tags. For that you'd need to declare your own global array of form pointers or std::vector. Unfortunately I can have multiple forms visible with different tags. I will read up on std::vector I can make each forms Caption unique by adding the LVIndex integer, does that make it simpler to find the form? Jack Back to top Andrue Cope [TeamB] Guest Posted: Tue Jun 22, 2004 1:42 pm    Post subject: Re: Find an Instance of a form Jack Mills wrote: Quote: I can make each forms Caption unique by adding the LVIndex integer, does that make it simpler to find the form? It could, yes but another solution is actually to iterate through the components owned by the application. You could probably use the following (untested code): for( int index=0; index<Application->ComponentsCount; ++index ) { TEM_DetailForm * tmp= dynamic_cast<TEM_DetailForm *>( Application->Components[ index ] ); if( tmp ) { // tmp now points to an instance of a TEM_DetailForm. } } If your app is an MDI app and these are MDI children you should iterate through your main form's MDIChildren array in much the same way. -- Andrue Cope [TeamB] [Bicester, Uk] http://info.borland.com/newsgroups/guide.html Back to top Jack Mills Guest Posted: Tue Jun 22, 2004 2:29 pm    Post subject: Re: Find an Instance of a form Thanks Andrue Should your code example be placed here <<<<<< ? void __fastcall TEditorChildDG::Edit1Click(TObject *Sender, int LVIndex) { <<<<<<< TEM_DetailForm *EM_Detail; EM_Detail = new TEM_DetailForm(this); EM_Detail->Query1->DatabaseName = Query1->DatabaseName; EM_Detail->Query1->Tag = LVIndex; ; EM_Detail->Caption = Caption; EM_Detail->Show(); } When placed here <<< the ComponentCount is always 3, no matter how many forms are open. Quote: If your app is an MDI app and these are MDI children you should iterate through your main form's MDIChildren array in much the same way. The app is a MDI app but the form I am checking for the EM_Detail form is not a MDIForm (parent) it is also a MDIChild. Jack Back to top Hans Galema Guest Posted: Tue Jun 22, 2004 2:54 pm    Post subject: Re: Find an Instance of a form Jack Mills wrote: Quote: Should your code example be placed here <<<<<< ? Yes. Quote: When placed here <<< the ComponentCount is always 3, no matter how many forms are open. Do use Screen->Forms[] instead of Application->Components[]. Quote: The app is a MDI app but the form I am checking for the EM_Detail form is not a MDIForm (parent) it is also a MDIChild. Screen->Forms[] does not care about being MDI or not. Hans. Back to top Jack Mills Guest Posted: Tue Jun 22, 2004 3:43 pm    Post subject: Re: Find an Instance of a form Thanks Hans I did this, which appears to work well. for(int index=0; index < Application->ComponentCount; ++index ) { TEM_DetailForm *tmp = dynamic_cast<TEM_DetailForm *>(Screen->Forms[index]); //Application->Components if( tmp ) { // tmp now points to an instance of a TEM_DetailForm. if(tmp->Query1->Tag == LVIndex) { tmp->BringToFront(); return; } } } But is the Application->ComponentCount correct in the for loop? I tried Screen->Forms->MDIChildCount but the complier complained of "Too few parameters". Otherwise it seems to function as desired. Jack Back to top Andrue Cope [TeamB] Guest Posted: Tue Jun 22, 2004 3:43 pm    Post subject: Re: Find an Instance of a form Hans Galema wrote: Quote: When placed here <<< the ComponentCount is always 3, no matter how many forms are open. Do use Screen->Forms[] instead of Application->Components[]. /That's/ where it is. I looked and looked for that and couldn't find it. -- Andrue Cope [TeamB] [Bicester, Uk] http://info.borland.com/newsgroups/guide.html Back to top Andrue Cope [TeamB] Guest Posted: Tue Jun 22, 2004 3:45 pm    Post subject: Re: Find an Instance of a form Jack Mills wrote: Quote: But is the Application->ComponentCount correct in the for loop? I wouldn't think so. Application::ComponentCount is the total in Application::Components. A little deductive reasoning suggests that TScreen::Forms would have its total specified by... ...TScreen::FormCount :) -- Andrue Cope [TeamB] [Bicester, Uk] http://info.borland.com/newsgroups/guide.html Back to top Jack Mills Guest Posted: Tue Jun 22, 2004 4:08 pm    Post subject: Re: Find an Instance of a form Of Course, it takes a little time for me to get there. for(int index=0; index < Screen->FormCount; ++index ) { TEM_DetailForm *tmp = dynamic_cast<TEM_DetailForm *>(Screen->Forms[index]); if( tmp ) { // tmp now points to an instance of a TEM_DetailForm. if(tmp->Query1->Tag == LVIndex) { tmp->BringToFront(); return; } } } Many Thanks to you Andrue & to you Hans. Jack Back to top Andrue Cope [TeamB] Guest Posted: Tue Jun 22, 2004 4:10 pm    Post subject: Re: Find an Instance of a form Jack Mills wrote: Quote: Of Course, it takes a little time for me to get there. No problem. I was getting a little frustrated at not finding the property Hans did. I /knew/ I'd used one once but it must have been too long ago. -- Andrue Cope [TeamB] [Bicester, Uk] http://info.borland.com/newsgroups/guide.html Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         BorlandTalk.com Forum Index -> C++ Builder (VCL Components Usage) All times are GMT Page 1 of 1   Jump to: Select a forum C++ Builder Newsgroups----------------C++ BuilderC++ Builder (ActiveX)C++ Builder (Announcements)C++ Builder (Command Line Tools)C++ Builder DatabasesC++ Builder Databases (ADO)C++ Builder Databases (Desktop)C++ Builder Databases (InterBase Express)C++ Builder Databases (Multi-Tier)C++ Builder Databases (SQL Servers)C++ Builder (Graphics)C++ Builder (IDE)C++ Builder (Internet)C++ Builder (Internet Socket)C++ Builder (Internet Web)C++ Builder (Jobs)C++ Builder (Language)C++ Builder (Language C++)C++ Builder (Compatibility with MFC)C++ Builder (Native API)C++ Builder (Non-Technical)C++ Builder (Students)C++ Builder (Third Party Tools)C++ Builder (Upgrade)C++ Builder (VCL)C++ Builder (VCL Components Usage)C++ Builder (VCL Components Development)C++ Builder (VCL Usage)C++ Builder (WinAPI)C++ Builder Installation Delphi Newsgroups----------------Delphi (General)Delphi ActiveX Controls UsageDelphi ActiveX Controls DevelopmentDelphi As400Delphi DatabasesDelphi Databases (ADO)Delphi Databases (dbExpress)Delphi Databases (Desktop)Delphi Databases (InterBase Express)Delphi Databases (Multi-Tier)Delphi Databases (SQL Servers)Delphi DeploymentDelphi GraphicsDelphi IDEDelphi InternationalizationDelphi InternetDelphi Internet Isapi-WebBrokerDelphi Internet WebSnapDelphi Internet WinsockDelphi JobsDelphi Language BASMDelphi Language ObjectPascalDelphi Model Driven Architecture (General)Delphi Model Driven Architecture (Third Party)Delphi MultimediaDelphi Native APIDelphi Non-TechnicalDelphi ObjectPascalDelphi OLE AutomationDelphi OO designDelphi OpenToolsAPIDelphi Reporting-ChartingDelphi RTLDelphi StudentsDelphi TeamSourceDelphi Thirdparty ToolsDelphi Thirdparty Tools (General)Delphi Thirdparty Tools (IntraWeb)Delphi Thirdparty Tools (RaveReports)Delphi UpgradeDelphi VCLDelphi VCL ComponentsDelphi VCL Components UsingDelphi VCL Components WritingDelphi WebServices SOAPDelphi WinAPIDelphi XMLDelphi Installationcomp.lang.pascal.delphi.components.misccomp.lang.pascal.delphi.components.usagecomp.lang.pascal.delphi.components.writingcomp.lang.pascal.delphi.databasescomp.lang.pascal.delphi.misccomp.sources.delphi JBuilder Newsgroups----------------JBuilderJBuilder AnnouncementsJBuilder Applet IssuesJBuilder As400JBuilder CompilerJBuilder CORBA/RMIJBuilder DatabasesJBuilder DB SwingJBuilder DebuggerJBuilder DeploymentJBuilder DocumentationJBuilder EnterpriseJBuilder HandheldJBuilder IDEJBuilder JavaJBuilder JavaAPIJBuilder Java LanguageJBuilder Java SwingJBuilder Java BeansJBuilder Java Beans UsageJBuilder Java Beans DevelopmentJBuilder JBCLJBuilder JDataStoreJBuilder JobsJBuilder LinuxJBuilder MacintoshJBuilder & MobileSetJBuilder MultiLingual AppsJBuilder Non-TechnicalJBuilder OpenToolsJBuilder Servlets (JSP)JBuilder StudentsJBuilder Team DevelopmentJBuilder Thirdparty ToolsJBuilder UpgradeJBuilder Installation InterBase Newsgroups----------------InterBaseInterBase Bug DiscussionInterBase GeneralInterBase IBConsoleInterBase OpenSourceInterBase ReplicationInterBase SQLInterBase ThirdpartyInterBase Installation Miscellaneous Borland Newsgroups----------------AppCenterAppServerEnteraVisiBroker  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.