BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Help with BO design          BorlandTalk.com Forum Index -> Delphi OO design View previous topic :: View next topic   Author Message Kern Carboni Guest Posted: Sat Feb 19, 2005 7:36 am    Post subject: Help with BO design Kiaora; I am new to Delphi (1+ year) and was lucky enough to find this newsgroup which has proved invaluable for my foray in OO; Our current Radiology system is an Informix 3, dos based system, which I have inherited in my new role. I have dedicated my sanity to providing a modern GUI system and wanted to start on a good footing by having the good people of this NG provide some guidance. My initial ramblings produced TBusinessObject Quote: _TPersistentBusinessObject _TVisit _TVisitReport _TVisiReportLine _TPatient _TDoctor TBusinesObjectCollection; Quote: _TPatientCollection _TVisitReportLineCollection TBusinessObjectIterator; I understand the following (hopefully); Without an OPF the BusinessCollection must have a mechanism of populating itself ie SQL query; Is the BusinessCollection responsible for the creation of the contained object ie. the TVisitReportLineCollection will iterate though the returned SQL result set, creating and populating visitReportLine objects and adding them to itself? Thanks in advance Kern Carboni Fulford Radiology Services New Zealand Back to top Bob Dawson Guest Posted: Sat Feb 19, 2005 8:30 am    Post subject: Re: Help with BO design "Kern Carboni" wrote Quote: My initial ramblings produced TBusinessObjectIterator; Your domain--won't comment except to say that iteration is a generic facility, not something peculiar to BOs, so I'd go for a very generic IIterable interface with an equally general (but extensible) TIterator class. Quote: Without an OPF the BusinessCollection must have a mechanism of populating itself ie SQL query; Two schools of thought--either do that, or else have an external service to which you can pass the collection for population. Needn't be a ful OPF--could be just a helper class. Quote: Is the BusinessCollection responsible for the creation of the contained object Again, you can either do that or externalize the function in a helper class. Might look something like this class procedure TBOCollection_DataSet_Adapter.PopulateCollection(aDataset : TDataset; aCollection: TBusinesObjectCollection); begin aDataset.First; while not aDataset.EOF do begin aCollection.AddItem(aCollection.ContainedClass.CreateFromDataRow(aDataSet)); aDataset.Next; end; end; Not production code obviously--just food for thought. bobD Back to top Kern Carboni Guest Posted: Sat Feb 19, 2005 10:37 am    Post subject: Re: Help with BO design Hi Bob Thanks for response; Quote: aCollection.AddItem(aCollection.ContainedClass.CreateFromDataRow(aDataSet)); Would I be correct in assuming ContainedClass would be a property containing class reference of the type being held in the collection? Is it feasible to set this in a constructor? Before posting I had read the post below and it has added to my confusion regarding collections and item creation. Quote: An Order is a composition in which the Order Lines do not have a life outside of the Order; if you want to create an OrderLine, then you have to ask the Order to create it; if you want to delete an Order Line then you have to ask the Order to delete it. How would I decipher this in light of your earlier response? I currently have a VisitReport ---> VisitReportLineCollection - which would qualify as a composition? Apologies for the mundane questions. Regards Kern Back to top Bob Dawson Guest Posted: Sat Feb 19, 2005 7:47 pm    Post subject: Re: Help with BO design "Kern Carboni" wrote Quote: Would I be correct in assuming ContainedClass would be a property containing class reference of the type being held in the collection? Is it feasible to set this in a constructor? Yep. If you have a base TBusinessObject with an appropriate virtual constructor, then you'd define the collection constructor as //given TBOClass = class of TBusinessObject; constructor TBusinessObjectCollection.Create(aBOClass : TBOClass); Now in your TPersistentBusinessObject class you can do class function TPersistentBusinessObject.ProvideCollection : TBusinessObjectCollection; begin Result := TBusinessObjectCollection.Create(self); end; Quote: ask the Order to create it; if you want to delete an Order Line then you have to ask the Order to delete it. That's would be normal approach. Quote: How would I decipher this in light of your earlier response? Not sure where you're seeing the disconnect--can you be a bit more specific? In general, remember that there are often differences between the way things appear to work and what's actually going on--especially once one starts to separate out different architectural layers. For example, I might write a line like newOrderLine := TOrder.AddLine; but that doesn't mean that internally TOrder actually knows how to do this--it may be just passing off the details to a service class and shielding the app programmer from the complexities underneath. An OPF can be ducklike (smooth and graceful above, paddling like mad underneath). Quote: Apologies for the mundane questions. Not an issue. Some of the simplest questions have led to threads lasting weeks. Like "Should a persistent object have a Save method?" Opinions differ. :-) bobD Back to top Kern Carboni Guest Posted: Sun Feb 20, 2005 12:31 am    Post subject: Re: Help with BO design Hi Bob I think I was missing the connection due to inexperience in knowing which predefined methods should appear in various objects in the application layers. ie. a TBusinessObject would have an AddLine method to create a single instance and add to collection and (now I'm hoping for the connection) there would also be a method to load the collection in one hit (sans OPF) ie AddLines(!!) which would eventually fire TBOCollection_DataSet_Adapter.PopulateCollection(aDataset: TDataset; aCollection: TBusinesObjectCollection); Regards Kern "Bob Dawson" <RBDawson (AT) prodigy (DOT) net> wrote Quote: "Kern Carboni" wrote How would I decipher this in light of your earlier response? Not sure where you're seeing the disconnect--can you be a bit more specific? Back to top Bob Dawson Guest Posted: Sun Feb 20, 2005 2:24 am    Post subject: Re: Help with BO design "Kern Carboni" wrote Quote: ie. a TBusinessObject would have an AddLine method to create a single instance and add to collection Ahh--shorthand is throwing you off. Something like aLineItem := aOrder.AddLine; is really masking what's happening: the order object has an internal TOrderLineItemsCollection, and that collection does the real work, not the order instance. Additionally (just to be clear), I'd expect an AddLine method to be adding a new line item to the order, not loading an existing item. Quote: and (now I'm hoping for the connection) there would also be a method to load the collection in one hit (sans OPF) I have an OPF, but I think it's possible--how about this: First we have to talk about owned and unowned collections. If you think of an ad hoc (unowned) collection like the patients seen on Friday, I'd expect the application programmer to call a load method on the collection object FridaysPatients := TPatientConnection.Create; FridaysPatients.Load('ByDate',['18 Feb 2005']); Now making this work without an OPF in place would be tricky, but I imagine something like the following would work: Create a datamodule for the TPatient class. In that datamodule is one query having the SQL to load the patient class fields, and all other queries contain only where clauses. When the datamodule is created, a query manager records each query by name in a list. Now tracing the call FridaysPatients.Load('ByDate',['18 Feb 2005']); we have something like the patientcollection instance calls a protected class method of the patient collection class, which knows about the datamodule, so instance call FridaysPatients.Load('ByDate',['18 Feb 2005']); goes to class call class procedure TPatientCollection.Load( aCollection : TPatientCollection; const LoadCondition : string; paramVals : array of variant); Now the TPatientCollection class knows about the datamodule, so the call gets relayed to the query manager object. It finds the master query statement, and then appends the where clause from the 'ByDate' query (in its list), iterates the variant array assigning parameter values, and fires the query. Then, the query and collection instance as passed on to the Quote: TBOCollection_DataSet_Adapter.PopulateCollection(aDataset: TDataset; aCollection: TBusinesObjectCollection); lines so that the collection now has its objects. At that point the query can be discarded, and the call returns up the chain to the instance. An owned collection is different only in that the application programmer probably never loads the collection explicitly at all. Rather, one has a lazy loader something like property LineItems : TLineItemCollection read GetLineItems; function TOrder.GetLineItems : TLineItemCollection; begin if not assigned (FLineItems) then begin FLineItems := TLineItemCollection.Create; FLineItems.Load('ByOrderID', [self.ID]); end; Result := FLineItems; end; That's a pretty quick sketch of how the paddling underneath might work... bobD Back to top Bryan Crotaz Guest Posted: Wed Feb 23, 2005 7:17 pm    Post subject: Re: Help with BO design "Kern Carboni" <mlungu (AT) orcon (DOT) net.nz> wrote Quote: Kiaora; I am new to Delphi (1+ year) and was lucky enough to find this newsgroup which has proved invaluable for my foray in OO; Our current Radiology system is an Informix 3, dos based system, which I have inherited in my new role. I have dedicated my sanity to providing a modern GUI system and wanted to start on a good footing by having the good people of this NG provide some guidance. Before you go too much further, have a good look at Bold and ECO on the Borland website, and come to borland.public.delphi.modeldrivenarchitecture.general. That'll save you a lot of time writing your own OPF, and enable you to get straight down to your problem domain! Bryan 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.