BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Help please on how to approach this          BorlandTalk.com Forum Index -> Delphi OO design View previous topic :: View next topic   Author Message Ant Guest Posted: Sat Feb 19, 2005 1:06 am    Post subject: Help please on how to approach this Hello all :) I am still trying to comprehend all the OO features that Delphi(7) has to offer, and am struggling with how to implement this design. I am sure it is not a new idea, but the design I have in mind will hopefully save me some serious code rewriting in the future. What I would like to achieve in summary is this. I want to be able to display some data in any control I choose, whether this be a treeview, a string grid, a memo or some other control that appears in the future or that I myself may build. The source of the data could be from anything a text file, a dataset, SQL Query, a cds database or just about anything. These are my thoughts on how I could implement this, but I am not experienced enough or confident enought to know how to start this. The idea is basically this A Parent class with some basic virtual functions that will apply to the decendant classes these would be Display( used to show the data in the control ) Update ( used to update data in the control due to changes from data source ) GetData ( used to obtain the data source ) These I imagine will apply to the Majority of controls I would use to represent this data. I would call the Parent Class DataView or something I would then inherit from this class and implement the inherited virtual functions specific to that control. For instance the treeview control would require the most work out of all the controls I would imagine, especially if it is represent the data in a heirarchal view, lots of thing would need to happen like building tree nodes, images to represent the nodes (possibly). Now in the view part of my program I just want the view part of the program to display the data according to the control selected. and the control would know how to respond to certain events, like a refresh ( the update function ) draw ( display function ) load data ( get data function ). I know this has something to do with Polymorphism, and that by declaring the Parent class functions as virtual, and implementing these in the derived classes, I would simply create an object of Dataview, and assign it reference of one of the controls and then by simply calling the function, it will execute the correct function according to the control it has reference to? I have also read about design patterns, unfortunately I don't seem to have understood them as well as I thought. I once read a really interesting article on Joanna Carter's teamb blog page on MVP, but sadly this does not seem to be there any longer. I am not entirely sure this is what I would be needing anyway, as controls will most likely be known at design time, with a possibilty of of dynamic controls being added. All I want to achieve is a type of framework that in the future will allow me to reuse these class framework in any new apps I build with little or no recoding. For instance one app might implement a treeview, and by simply adding this to the form and implementing some code to use the Dataview classes will just work, by using the prebuilt classes. I have also seen a very very brief intro of Interfaces, and am unsure if this would fit in better than classes? Any advice ( except dont do it ) pointers, links to tutorials or anything that would allow me to implement this before it becomes a fragmented patrticle floating around in the brain :) Thanks in advance, sorry the post is a bit long Back to top Joanna Carter (TeamB) Guest Posted: Sat Feb 19, 2005 9:28 am    Post subject: Re: Help please on how to approach this "Ant" <Ant (AT) nowhere (DOT) com> a écrit dans le message de news: [email]42169116 (AT) newsgroups (DOT) borland.com[/email]... Quote: I want to be able to display some data in any control I choose, whether this be a treeview, a string grid, a memo or some other control that appears in the future or that I myself may build. You certainly do need the MVP framework for something like this; it totally separates the UI from the BO layer and you could always adapt it so that the View classes were Adapters that know how to talk to a control rather than being a control. Quote: I once read a really interesting article on Joanna Carter's teamb blog page on MVP, but sadly this does not seem to be there any longer. The articles are on my website www.carterconsulting.org.uk You would also benefit from looking at OPFs (Object Persistence Frameworks) as these will separate out all the data manipulation code from you business logic. Both MVP and OPF are better facilitated by using using a Value Type Framework rather than relying on RTTI and you want to Google on this group for the many discussions and examples that have been posted here. Quote: I have also seen a very very brief intro of Interfaces, and am unsure if this would fit in better than classes? Jim Cooper and I are at variance on this, but I found in Delphi for Win32, once you have started you have to use them almost everywhere, due to the problems with reference counting and the inability to cast from an interface to an object. Interfaces are useful but not as necessary in .NET; my designs for .NET don't use anywhere near as many interfaces as they did for Win32. Joanna -- Joanna Carter (TeamB) Consultant Software Engineer TeamBUG support for UK-BUG TeamMM support for ModelMaker Back to top Ant Guest Posted: Sun Feb 20, 2005 8:12 pm    Post subject: Re: Help please on how to approach this Quote: I want to be able to display some data in any control I choose, whether this be a treeview, a string grid, a memo or some other control that appears in the future or that I myself may build. You certainly do need the MVP framework for something like this; it totally separates the UI from the BO layer and you could always adapt it so that the View classes were Adapters that know how to talk to a control rather than being a control. Hello I just read your object store.zip articles, and found them very interesting, even though, I do not fully understand this yet. I think I may have done something like the MVP I am not sure. What I did was to Create a TreeViewHandler that took as an argument to it's constructor the treeview on the form, and a data source (currently a Stringlist container, which I got from Marco Cantu's Mastering Delphi 7 book made from a tab delimited file Using Peter Bellows String Parser Function ). And this then builds the data for the treeview in this class, a variable of this class is declared in the main form, so that it exists as long as the TTreeVIew control does. It uses a proxyNode class that holds a reference to a recordNode object in an object list, that holds all the record data. the TTreeNode Data property holds a pointer to the proxyNode, the Proxy node Hold the ID of the Record Node it Points to which is the same as the record id from the file or db, and also two other fields that are used to create a description for the TTReeNode. The problem with this TreeViewHandler Class right now is it is very specific to one database or textfile, all the fields for the RecordNode are hardcoded to match the database/text file. So I guess I am sort of on the right track here, but if I need to use this for another database, I would have to change the hardcoded filednames of the class, probably not a big thing now, but could get complicated as I had more functionality to the class that may have a dependency on certain fieldnames of the class. Quote: You would also benefit from looking at OPFs (Object Persistence Frameworks) as these will separate out all the data manipulation code from you business logic. Both MVP and OPF are better facilitated by using using a Value Type Framework rather than relying on RTTI and you want to Google on this group for the many discussions and examples that have been posted here. Ok now I would like to give my interpretation of the OPF, as I understand it, and welcome any corrections along the way :) A Business Object is an object that holds the fields of a record from a database for flatfile in an object? A collection of BO's are a list containing each created BO? The business logic is yet another object that holds the business rules about how and what data should be used, that will also hold a reference to a BO to see what fields the business logic will use? Then there are the graphic controls which re derivations of common Delphi controls, customised for use with Business Object and Business Logic, they represent the view of the data. However these controls are not tied to one particular type of BO or BL they will just have these as a reference and know how to display the data contained t=in the BO using the BL? So it could be summed up as something like this. BO = Business Object = Holds fieldnames from a data source BL = Business Logic = Holds all the functions procedures etc that manipulate the BO, maybe SQL Selects, Updates etc, grouping orders, and any busines rules that apply to the data, but instead of manipulating a database record they manipulate a BO? Views = Graphic Delphi controls = take a BO as a reference and display the data related to the filednames of the BO, regardless of what Fieldnames exist in the BO? Quote: I have also seen a very very brief intro of Interfaces, and am unsure if this would fit in better than classes? I still do not understand Interfaces, or rather how they should not be used with object references due to reference counting etc, I thought the idea of an interface was to allow for emulated multiple Inheritance So somewhere along the way an Object is going to have to exist somewhere that implements the interface? Your thoughts and comments welcome as to my understanding of OPF TIA Back to top Joanna Carter (TeamB) Guest Posted: Mon Feb 21, 2005 10:45 am    Post subject: Re: Help please on how to approach this "Ant" <Ant (AT) nowhere (DOT) com> a écrit dans le message de news: 4218ef11$1 (AT) newsgroups (DOT) borland.com... Quote: I just read your object store.zip articles, and found them very interesting, even though, I do not fully understand this yet. Don't worry, it took me two years to to get enough understanding to write them :-) Quote: The problem with this TreeViewHandler Class right now is it is very specific to one database or textfile, all the fields for the RecordNode are hardcoded to match the database/text file. This is not MVP, it is OPF. The OPF should take an object and delegate the retrievel/storage to a base handler type which should have any methods that are common to all operations related to retrieving/storing an object. You then derive from the base handler class to allow you database-specific code. You can then choose which handler you want to use, even at runtime. Quote: So I guess I am sort of on the right track here, but if I need to use this for another database, I would have to change the hardcoded filednames of the class, probably not a big thing now, but could get complicated as I had more functionality to the class that may have a dependency on certain fieldnames of the class. The OPF handler should look after the translation of property names to/from field names. Quote: Ok now I would like to give my interpretation of the OPF, as I understand it, and welcome any corrections along the way :) A Business Object is an object that holds the fields of a record from a database for flatfile in an object? No, no, no!! Business Objects know nothing about databases at all. As I have just said, it is the responsibility of the OPF handlers to translate objects to tables. Quote: A collection of BO's are a list containing each created BO? Yes Quote: The business logic is yet another object that holds the business rules about how and what data should be used, that will also hold a reference to a BO to see what fields the business logic will use? Business logic can appear in both storable Bos and also BOs that are 'managers'. Most BOs have their own internal logic that manages their own responsibilities; things like calculating an Invoice Total from the Invoice Lines held inside the Invoice object. There are also other BOs whse responsibilities affect more than one type of object; for example, storing a Sales Order also affects the Customer Total Balance as well as the Stock Level for each Product included in the Order. This logic does not truly belong in any one class as it then ties that logic to a class that may not be able to see the entire BO model. Quote: Then there are the graphic controls which re derivations of common Delphi controls, customised for use with Business Object and Business Logic, they represent the view of the data. This is more to do with MVP. Quote: However these controls are not tied to one particular type of BO or BL they will just have these as a reference and know how to display the data contained t=in the BO using the BL? Certain controls can display any value type or list of objects, but you may need to derive custom controls for complex objects. Quote: So it could be summed up as something like this. BO = Business Object = Holds fieldnames from a data source No Quote: BL = Business Logic = Holds all the functions procedures etc that manipulate the BO, maybe SQL Selects, Updates etc, grouping orders, and any busines rules that apply to the data, but instead of manipulating a database record they manipulate a BO? No, BL is an integral part of a BO Quote: Views = Graphic Delphi controls = take a BO as a reference and display the data related to the filednames of the BO, regardless of what Fieldnames exist in the BO? Not quite. A View displays the properties of a BO; it has no knowledge of databases, fields or tables. Quote: I still do not understand Interfaces, or rather how they should not be used with object references due to reference counting etc, I thought the idea of an interface was to allow for emulated multiple Inheritance So somewhere along the way an Object is going to have to exist somewhere that implements the interface? If I were you, I would take it one step at a time and try to clear up your understanding of classes before you move into interfaces :-) Joanna -- Joanna Carter (TeamB) Consultant Software Engineer TeamBUG support for UK-BUG TeamMM support for ModelMaker Back to top Ant Guest Posted: Mon Feb 21, 2005 11:54 am    Post subject: Re: Help please on how to approach this Quote: Don't worry, it took me two years to to get enough understanding to write them That makes me feel better :) I think I need to do some more research/reading of this OPF thingy It took me a while to grasp basic OO polymorphism and inheritance. I know what I need, but do not understand enough to be able to implement this yet, which I find frustrating, hopefully practice will make things easier. I never really settled with any language during college, and learnt bits of C++, bits of Java, and bits of VB, but never felt entirely comfortable with any of these least of all Java. It wasn't until I found an article describing how to do something in Delphi that I started using Delphi, and glad I did, although I still try to learn C++ as well. Thanks for the help so far, I am off googling now until I understand more about this OPF idiom and will then no doubt return with more question Thanks Back to top Joanna Carter (TeamB) Guest Posted: Mon Feb 21, 2005 1:17 pm    Post subject: Re: Help please on how to approach this "Ant" <Ant (AT) nowhere (DOT) com> a écrit dans le message de news: 4219cbab$1 (AT) newsgroups (DOT) borland.com... Quote: It wasn't until I found an article describing how to do something in Delphi that I started using Delphi, and glad I did, although I still try to learn C++ as well. With the advent of .NET, you would be advised to move on to C#; it is very similar to C++ but without some of the peculiarities and gotchas, and it allows you to be able to write code in either Delphi or C# against the .NET runtime. Joanna -- Joanna Carter (TeamB) Consultant Software Engineer TeamBUG support for UK-BUG TeamMM support for ModelMaker Back to top Ant Guest Posted: Mon Feb 21, 2005 2:16 pm    Post subject: Re: Help please on how to approach this Joanna Carter (TeamB) wrote: Quote: "Ant" <Ant (AT) nowhere (DOT) com> a écrit dans le message de news: 4219cbab$1 (AT) newsgroups (DOT) borland.com... With the advent of .NET, you would be advised to move on to C#; it is very similar to C++ but without some of the peculiarities and gotchas, and it allows you to be able to write code in either Delphi or C# against the .NET runtime. I looked at C# early on, and was uncertain of C#'s future, I have heard many bad things and many good things about the language, one of the reasons I did not look at .Net is because our tutor told us ''.Net is not used anywhere near as much as Microsoft would have us believe, and many businesses are sceptical about using the .Net until it has proven not to be a new portal for the evils of worms and viruses.'' As to the merits of this I do not know, Delphi 8 came with my version of Delphi 7, but I have never used it. I think I need to stick to Delphi at the moment and try and learn and understand this powerful language before looking at others, the reason I still learn C++ as well is because I am still completing an online course. Delphi seems to offer a lot of what C++ does apart from MI, which as far as I can see I have never needed yet, and of course Delphi uses mainly references rather than pointers. I notice that Borland are also offering a C# solution perhaps in 6 monts from now, I can look at broadening my programming language skills to newer languages, I think mastering OOP will make things easier. From my little experience I have in programming so far one language is like the next differing only in syntax, and flexibility it allows the programmer, I can happily implement a stack in C++, Delphi or VB it will only be the syntax and how easily the language enables me to implement this that will be different, and perhaps limitations on what data types the stack could hold. Thank you for all the help and advice you have chosen to share, it is very much appreciated, and I no doubt will be picking your brains for more information sooner rather than later Thanks Back to top Lee_Nover Guest Posted: Mon Feb 21, 2005 2:20 pm    Post subject: Re: Help please on how to approach this Quote: I want to be able to display some data in any control I choose, whether this be a treeview, a string grid, a memo or some other control that appears in the future or that I myself may build. maybe something like this: http://leenover.homeip.net/isapi/pas2html.dll/pas2html?File=/delphi/projects/PyramidSales/ it's a really small example presenting data in a virtual treeview there are only presenters for the VTV but others can easily be added no real BO logic there .. just some examples this was actually my first try at a simple MVP .. it probably should have more classes that would really separate M from V from P :) Back to top Joanna Carter (TeamB) Guest Posted: Mon Feb 21, 2005 4:03 pm    Post subject: Re: Help please on how to approach this "Ant" <Ant (AT) nowhere (DOT) com> a écrit dans le message de news: 4219ecd5$1 (AT) newsgroups (DOT) borland.com... Quote: I think I need to stick to Delphi at the moment and try and learn and understand this powerful language before looking at others, the reason I still learn C++ as well is because I am still completing an online course. Delphi seems to offer a lot of what C++ does apart from MI, which as far as I can see I have never needed yet, and of course Delphi uses mainly references rather than pointers. There certainly isn't much mainstream programming that can't be done in Delphi. BTW Delphi does use pointers; every object variable is really a pointer, it's just that you don't have to explicitly de-reference them, that is taken care of by the compiler. Quote: I notice that Borland are also offering a C# solution perhaps in 6 monts from now, I can look at broadening my programming language skills to newer languages, I think mastering OOP will make things easier. Certainly, if you se the need to move to .NET, then Delphi 2005 is an ideal transitional tool as it supports Delphi for Win32, Delphi for .NET and C#, all in the one product. Joanna -- Joanna Carter (TeamB) Consultant Software Engineer TeamBUG support for UK-BUG TeamMM support for ModelMaker Back to top Ant Guest Posted: Tue Feb 22, 2005 6:37 pm    Post subject: Re: Help please on how to approach this Hi Lee Thanks very much for this, it is very helpful 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.