BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Nested Object Editions          BorlandTalk.com Forum Index -> Delphi OO design View previous topic :: View next topic   Author Message Gabriel GIbaut Guest Posted: Thu Jan 06, 2005 1:02 pm    Post subject: Nested Object Editions Hello, I have this situation: I´m editing objects so if i call Edit on an instance, it shows a form to edit itself (I.E: Employee.Edit). but some editions are nested, that is, while editing an employee i can edit his salary, so there is code in some place that class Salary.Edit( that shows another editor) and so on... The problem is that i need to commit the changes right after the edition (specs) but in the place where the first edition started, so depending if i´m nested or not i need to commit the changes or not. Nowadays the old code uses a property in the editor that says if it´s the first on the chain or not, and that assignment propagates all over the chain. I got this idea of a Transaction class with two sublasses: RealTransaction and FakeTransaction (this does nothing), and depending use one of them depending on the context. So the editing code is the same. But my problem still remains, how can I in an OO-Way determine if i´m nested or not? TIA Gabriel Back to top Bob Dawson Guest Posted: Thu Jan 06, 2005 3:09 pm    Post subject: Re: Nested Object Editions "Gabriel GIbaut" wrote Quote: I´m editing objects so if i call Edit on an instance, it shows a form to edit itself (I.E: Employee.Edit). but some editions are nested, that is, while editing an employee i can edit his salary, so there is code in some place that class Salary.Edit( that shows another editor) and so on... It's generally considered a bad idea for business objects to know anything about displaying themselves. To a certain extent you can finesse this by having a registration process (Salary knows that a editing class exists, and if one is registered calls it), but even that becomes problematic if your problem domain becomes complex. For example, one might often want to edit collected objects in a frame on the collection owner's edit form, rather than proliferating a bunch of sub-forms. Question: what's the sequencing relationshp between the forms and the transaction--when I finish with the Salary edit form (called from within editing an employee), does anything get persisted at that point? Does the salary edit form have both 'Ok' (accept the edits in memory but do nothing else) and 'Save' (accept and persist the changes) options? Quote: But my problem still remains, how can I in an OO-Way determine if i´m nested or not? My tendency is to say that the business object shouldn't care. That is, it simply issues a BeginTransaction request to the persistence layer, and a Commit when it's done. The persistence layer is then responsible for knowing whether it's already in a transaction context and so determining whether to issue an actual BeginTransaction call to the storage device or merely to increase the current transaction nesting level. bobD Back to top Gabriel GIbaut Guest Posted: Thu Jan 06, 2005 5:24 pm    Post subject: Re: Nested Object Editions "Bob Dawson" <bdawson (AT) idtdna (DOT) com> escribió en el mensaje news:41dd54c0$2 (AT) newsgroups (DOT) borland.com... Quote: It's generally considered a bad idea for business objects to know anything about displaying themselves. To a certain extent you can finesse this by having a registration process (Salary knows that a editing class exists, and if one is registered calls it), but even that becomes problematic if your problem domain becomes complex. For example, one might often want to edit collected objects in a frame on the collection owner's edit form, rather than proliferating a bunch of sub-forms. I didn´t think about it, you are right. The other option was an editor factory, but I suppose this is also going to get ugly when things become complex. But i don´t have much idea about what else can i do...Any idea? Quote: Question: what's the sequencing relationshp between the forms and the transaction--when I finish with the Salary edit form (called from within editing an employee), does anything get persisted at that point? Does the salary edit form have both 'Ok' (accept the edits in memory but do nothing else) and 'Save' (accept and persist the changes) options? As it´s implemented, the editor calls the persistence layer when it´s done, so it has a variable that says if it´s nested or not to make the call depending on the situation. That´s what i want to change. I tought about the transaction class, but i still need to pass it all over the place, like the variable. I´m trying to avoid this. Quote: My tendency is to say that the business object shouldn't care. That is, it simply issues a BeginTransaction request to the persistence layer, and a Commit when it's done. The persistence layer is then responsible for knowing whether it's already in a transaction context and so determining whether to issue an actual BeginTransaction call to the storage device or merely to increase the current transaction nesting level. The problem is the persistence layer as today, does no have nested transactions. TIA Gabriel Back to top Bob Dawson Guest Posted: Thu Jan 06, 2005 6:02 pm    Post subject: Re: Nested Object Editions "Gabriel GIbaut" wrote Quote: But i don´t have much idea about what else can i do...Any idea? I generally think of application workflow as a layer separate from the business objects, and don't try to do much in terms of the OPF design to support it. That's an issue for the application programmer to address. For a much more systematic approach visit Joanna's website and look at her MVP stuff. www.carterconsulting.org.uk Quote: The problem is the persistence layer as today, does no have nested transactions. It's still going to be much easier to teach the persistence layer to handle this than to try to have the individual business objects try to track or figure out where they fit into the application's ongoing process. By 'persistence layer' I don't mean the database itself, but rather a layer of code behind the buisiness objects that receives all BO requests for persistence actions and processes them. All persistence actions pass through this layer, so it can easily remember what the current transaction state is. bobD Back to top Gabriel GIbaut Guest Posted: Thu Jan 06, 2005 8:14 pm    Post subject: Re: Nested Object Editions Bob, Thanks Again. Quote: It's still going to be much easier to teach the persistence layer to handle this than to try to have the individual business objects try to track or figure out where they fit into the application's ongoing process. By 'persistence layer' I don't mean the database itself, but rather a layer of code behind the buisiness objects that receives all BO requests for persistence actions and processes them. All persistence actions pass through this layer, so it can easily remember what the current transaction state is. The problem is I have no voice when it comes to the persistence layer we are using, i suppose i´ll end up passing a transaction object everywhere, or the Nested indicator variable, but i´m going to get forced to use one editor after another with nothing in between ( because if I don´t the BOare going to get polluted with the "nested" parameter) Thanks Gabriel Back to top Bob Dawson Guest Posted: Thu Jan 06, 2005 8:26 pm    Post subject: Re: Nested Object Editions "Gabriel GIbaut" wrote Quote: The problem is I have no voice when it comes to the persistence layer we are using, Bummer. Are there ever multiple transactions open? If not you might simply create a singleton transaction holder. When an object wants a transaction then it just requests one from the holder, which returns a transaction token. The holder can either create a new transaction (no tokens are out, so the item is not nested) or else just inc() a counter when returning the token (the item is nested in another's transaction). That way at least the BO doesn't have to figure out what the current processing state is. When all tokens have been returned, the holder singleton knows that we're back at the outermost object and the transaction can be fired. That's essentially how transaction nesting works in the persistence layer anyway. bobD Back to top Gabriel GIbaut Guest Posted: Fri Jan 07, 2005 11:49 am    Post subject: Re: Nested Object Editions Bob, thanks again. The problem is they have plans to support multiple transactions, so I suppose i´m going to need to program a multiple transaction mechanism, and from there, call the persistence layer mechanism. Gabriel "Bob Dawson" <bdawson (AT) idtdna (DOT) com> escribió en el mensaje news:41dd9eda$1 (AT) newsgroups (DOT) borland.com... Quote: "Gabriel GIbaut" wrote The problem is I have no voice when it comes to the persistence layer we are using, Bummer. Are there ever multiple transactions open? If not you might simply create a singleton transaction holder. When an object wants a transaction then it just requests one from the holder, which returns a transaction token. The holder can either create a new transaction (no tokens are out, so the item is not nested) or else just inc() a counter when returning the token (the item is nested in another's transaction). That way at least the BO doesn't have to figure out what the current processing state is. When all tokens have been returned, the holder singleton knows that we're back at the outermost object and the transaction can be fired. That's essentially how transaction nesting works in the persistence layer anyway. bobD 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.