BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  singleton references          BorlandTalk.com Forum Index -> Delphi OO design View previous topic :: View next topic   Author Message Brad White Guest Posted: Wed Oct 29, 2003 9:34 pm    Post subject: singleton references It's getting so that I have a small number of singletons running around that handle support roles. In some projects, I've had sort of a master controller that held references to these. I'm not thrilled with this because you quickly run afoul of the Law of Demeter, e.g. the more dots, the more coupled your objects. OTOH, I am not completely comfortable with lots of these global references running around either. Your preference? Other ideas? -- Thanks, Brad White Back to top Joanna Carter Guest Posted: Wed Oct 29, 2003 9:43 pm    Post subject: Re: singleton references Brad White wrote: Quote: Your preference? Other ideas? Use a class of class methods. Any instance data can be held in implementation section variables. Joanna -- Joanna Carter Consultant Software Engineer TeamBUG support for UK-BUG TeamMM support for ModelMaker Back to top Lawrence Thurman Guest Posted: Thu Oct 30, 2003 5:00 pm    Post subject: Re: singleton references If the singleton is written to the true form o a singleton pattern then you should not have to have Global variables I override the NewInstance method from TObject to control whether or no the Class instantiates or just updates the refcount all of this is encapsualted with a class; however you can not inherit from this class why? think about it - you would have to override everything that is controlling the singleton otherwise there qould be one class - the child XOR the parent hope this helps "Brad White" <bwhite at inebraska.com> wrote Quote: It's getting so that I have a small number of singletons running around that handle support roles. In some projects, I've had sort of a master controller that held references to these. I'm not thrilled with this because you quickly run afoul of the Law of Demeter, e.g. the more dots, the more coupled your objects. OTOH, I am not completely comfortable with lots of these global references running around either. Your preference? Other ideas? -- Thanks, Brad White Back to top Danny Heijl Guest Posted: Thu Oct 30, 2003 7:57 pm    Post subject: Re: singleton references Quote: however you can not inherit from this class You can inherit from this singleton class by Lucian Radulescu : http://www.ez-delphi.com/sources/usingle.htm Danny --- Back to top Brad White Guest Posted: Thu Oct 30, 2003 8:26 pm    Post subject: Re: singleton references "Lawrence Thurman" <lawrence (AT) powerofzen (DOT) com> wrote Quote: however you can not inherit from this class why? think about it - you would have to override everything that is controlling the singleton otherwise there qould be one class - the child XOR the parent John, Do you want to answer this or should I? -- Thanks, Brad White Back to top Lawrence Thurman Guest Posted: Mon Nov 03, 2003 5:42 pm    Post subject: Re: singleton references But if you inherit from TAClass with TChild1 and TChild2 and polymorph each of the children I believe that you can only construct one of the other, but trying to construct both will not happen due to the refcount being incremented. "Danny Heijl" <danny.heijl_ (AT) _pandora (DOT) be> wrote Quote: however you can not inherit from this class You can inherit from this singleton class by Lucian Radulescu : http://www.ez-delphi.com/sources/usingle.htm Danny --- Back to top John Elrick Guest Posted: Mon Nov 03, 2003 11:06 pm    Post subject: Re: singleton references "Brad White" <bwhite at inebraska.com> wrote Quote: "Lawrence Thurman" <lawrence (AT) powerofzen (DOT) com> wrote in message news:3fa1438a (AT) newsgroups (DOT) borland.com... however you can not inherit from this class why? think about it - you would have to override everything that is controlling the singleton otherwise there qould be one class - the child XOR the parent John, Do you want to answer this or should I? Well...it's true, using that pattern. It's one of the reasons I adopted the IFooFactory approach instead. John Back to top John Elrick Guest Posted: Mon Nov 03, 2003 11:52 pm    Post subject: Re: singleton references "Brad White" <bwhite at inebraska.com> wrote Quote: It's getting so that I have a small number of singletons running around that handle support roles. In some projects, I've had sort of a master controller that held references to these. I'm not thrilled with this because you quickly run afoul of the Law of Demeter, e.g. the more dots, the more coupled your objects. Very true. Quote: OTOH, I am not completely comfortable with lots of these global references running around either. Your preference? Other ideas? I wouldn't worry too much until there is a real issue to address. If you have 100 valid Singletons, then you have 100 valid Singletons. OTOH, if you do notice the bad smells of large uses clauses, difficulty in locating the "correct" Singleton, or "if only this Singleton did _this_", then I would say it is time to refactor the code. The design will speak to you. John Back to top Brad White Guest Posted: Thu Nov 06, 2003 8:04 pm    Post subject: Re: singleton references "John Elrick" <jelrick (AT) adelphia (DOT) net> wrote Quote: I wouldn't worry too much until there is a real issue to address. If you have 100 valid Singletons, then you have 100 valid Singletons. OTOH, if you do notice the bad smells of large uses clauses, difficulty in locating the "correct" Singleton, or "if only this Singleton did _this_", then I would say it is time to refactor the code. The design will speak to you. Trust the source... -- Thanks, Brad White Back to top John Elrick Guest Posted: Fri Nov 07, 2003 2:48 pm    Post subject: Re: singleton references "Brad White" <bwhite at inebraska.com> wrote Quote: "John Elrick" <jelrick (AT) adelphia (DOT) net> wrote in message news:3fa6ea28$2 (AT) newsgroups (DOT) borland.com... I wouldn't worry too much until there is a real issue to address. If you have 100 valid Singletons, then you have 100 valid Singletons. OTOH, if you do notice the bad smells of large uses clauses, difficulty in locating the "correct" Singleton, or "if only this Singleton did _this_", then I would say it is time to refactor the code. The design will speak to you. Trust the source... And your gut<g> John Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         BorlandTalk.com Forum Index -> Delphi OO design 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.