BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  ValueType Framework help please Goto page 1, 2  Next          BorlandTalk.com Forum Index -> Delphi OO design View previous topic :: View next topic   Author Message Quicoli Guest Posted: Fri Dec 10, 2004 2:19 pm    Post subject: ValueType Framework help please Hi all ! i have printed all posts i found here about ValueType Framework, to try implementing it here. But i'm getting confused about registering the metadata. Sometime Joanna exposed her code for us, but sometimes using interfaces other no interfaces... i'm thankfull for her help ! I would like some code example, but if possible please, a little complete code. I know sometimes you maybe think "i got hard to develop this and now are asking me for expose my code...." I just need a real code to begin my "adventures" in the "valuetype world" :) thanks for helping me !!!! -- Paulo R. Quicoli --------------------- Analista Programador Control-M Informática Ltda. Back to top Joanna Carter (TeamB) Guest Posted: Fri Dec 10, 2004 2:50 pm    Post subject: Re: ValueType Framework help please "Quicoli" <paulo (AT) controlm (DOT) com.br> a écrit dans le message de news: [email]41b9a1dd (AT) newsgroups (DOT) borland.com[/email]... Quote: I just need a real code to begin my "adventures" in the "valuetype world" If you have read my examples of Value Types, then you have the best part of the Value Type framework. You may want to add further Metadata to the base ValueType class, but whether you use interfaces or classes is not relevant to the implementation. The whole purpose of the Value Type is to provide a better system of RTTI than is already available in Delphi. To a certain extent some of these features are not as relevant in the .NET framework as it is possible to query any type just using reflection. Once you decide how much extra metadata you need you can then set about using the RTTI that the Value Type framework provides to build either/both an OPF and/or a GUI framework. The code for either of these frameworks is not a simple matter, but you can look at the (incomplete) articles on my website. Full source code for such things would be subject to copyright and also subject to fees :-) Joanna -- Joanna Carter (TeamB) Consultant Software Engineer TeamBUG support for UK-BUG TeamMM support for ModelMaker Back to top Iman L Crawford Guest Posted: Fri Dec 10, 2004 3:20 pm    Post subject: Re: ValueType Framework help please Quicoli <paulo (AT) controlm (DOT) com.br> wrote in news:41b9a1dd (AT) newsgroups (DOT) borland.com: Quote: I would like some code example, but if possible please, a little complete code. I have some code that does things similar to ValueType. It's just me playing around and not really ready for any production work. The code is uncommented. It won't work with Delphi.NET (uses implements keyword). I've been meaning to place it at CodeCentral. I'll see if I can get it in some type of usuable form today. -- Iman Back to top Joanna Carter (TeamB) Guest Posted: Fri Dec 10, 2004 4:00 pm    Post subject: Re: ValueType Framework help please "Quicoli" <paulo (AT) controlm (DOT) com.br> a écrit dans le message de news: [email]41b9c3f4 (AT) newsgroups (DOT) borland.com[/email]... Quote: Question 1: =========== I'm implementing a TStringMetadata.GetMetadata like this: function TStringMetadata.GetMetadata: IMetadata; begin Result := (TStringMetadata.Create as IMetadata); end; Why would you ask a class that couold just as well implement IMetadata to give you a reference via a method ? If TStringMetadata derives from TMetadata and TMetadata implements IMetadata, then you can get your IMetadata simply by asking the either the Value Type or the Type Register. TValueType = class(...) .... function GetMetadata: IMetadata; virtual; abstract; end; TStringValueType = class(TValueType, ...) .... function GetMetadata: IMetadata; override; end; function TStringValueType.GetMetadata: IMetadata; begin Result := TStringMetadata.Create; end; Quote: But i'm thinking if i need to have reference (a private field) to IMetadata in my TStringAttribute to avoid duplicated creation of TStringMetadata when using something like: CurrentItem.GetMetadata.GetType CurrentItem.GetMetadata.GetName You could always create the metadata on first call and then maintain it until the ValueType dies. Quote: Question 2: ========== Well, where should i create the TStringMetadata, In my TStringAttribute.GetMetadata or at TypeRegister ? Either one would work depending on your overall strategy. Joanna -- Joanna Carter (TeamB) Consultant Software Engineer TeamBUG support for UK-BUG TeamMM support for ModelMaker Back to top Quicoli Guest Posted: Fri Dec 10, 2004 4:44 pm    Post subject: Re: ValueType Framework help please Joanna Carter, Thank you for your help and attention. I understand your point of view, and respect it. So, i gonna look for your advices which are like a light in the night :) Question 1: =========== I'm implementing a TStringMetadata.GetMetadata like this: function TStringMetadata.GetMetadata: IMetadata; begin Result := (TStringMetadata.Create as IMetadata); end; But i'm thinking if i need to have reference (a private field) to IMetadata in my TStringAttribute to avoid duplicated creation of TStringMetadata when using something like: CurrentItem.GetMetadata.GetType CurrentItem.GetMetadata.GetName Question 2: ========== Well, where should i create the TStringMetadata, In my TStringAttribute.GetMetadata or at TypeRegister ? Again, thank you ! Joanna Carter (TeamB) wrote: Quote: -- Joanna Carter (TeamB) Consultant Software Engineer TeamBUG support for UK-BUG TeamMM support for ModelMaker -- Paulo R. Quicoli --------------------- Analista Programador Control-M Informática Ltda. Back to top Quicoli Guest Posted: Fri Dec 10, 2004 5:01 pm    Post subject: Re: ValueType Framework help please Iman L Crawford wrote: Quote: I have some code that does things similar to ValueType. It's just me playing around and not really ready for any production work. The code is uncommented. It won't work with Delphi.NET (uses implements keyword). I've been meaning to place it at CodeCentral. I'll see if I can get it in some type of usuable form today. Iman, thanks for openning your code ! I hope you code get my mind open to understand more about Attribute framework. I will see your ideias an try to get good concepts from your code... really thanks ! -- Paulo R. Quicoli --------------------- Analista Programador Control-M Informática Ltda. Back to top Iman L Crawford Guest Posted: Fri Dec 10, 2004 10:53 pm    Post subject: Re: ValueType Framework help please Quicoli <paulo (AT) controlm (DOT) com.br> wrote in news:41b9c7b4 (AT) newsgroups (DOT) borland.com: Quote: thanks for openning your code ! I hope you code get my mind open to understand more about Attribute framework. I will see your ideias an try to get good concepts from your code... Done: http://cc.borland.com/codecentral/ccWeb.exe/listing?id=22876 This is a proof of concept and a work in progress. If anyone has questions, comments or critiques post here. -- Iman Back to top Joanna Carter (TeamB) Guest Posted: Fri Dec 10, 2004 11:22 pm    Post subject: Re: ValueType Framework help please "Iman L Crawford" <ilcrawford.at.hotmail.dot.com> a écrit dans le message de news: Xns95BBABDF872F8ilcrwfrd (AT) 207 (DOT) 105.83.66... Quote: This is a proof of concept and a work in progress. If anyone has questions, comments or critiques post here. I would be surprised if this compiles :-) You have forward declarations of interface types that are not completely defined before the classes that use them; this causes problems that the methods mentioned in the full declaration, aren't visible in classes declared before that, even with the forward declaration. When you are going to the trouble to create your own Value Type framework, why would you bother using Delphi RTTI as well ? Joanna -- Joanna Carter (TeamB) Consultant Software Engineer TeamBUG support for UK-BUG TeamMM support for ModelMaker Back to top Iman L Crawford Guest Posted: Sat Dec 11, 2004 4:43 am    Post subject: Re: ValueType Framework help please "Joanna Carter (TeamB)" <joanna (AT) nospam (DOT) co.uk> wrote in news:41ba2fd1 @newsgroups.borland.com: Quote: I would be surprised if this compiles Be suprised. If I read the help correctly, forward declared interfaces are no different that forward declared classes. It works without in AV's so far. Quote: When you are going to the trouble to create your own Value Type framework, why would you bother using Delphi RTTI as well ? I didn't want to have to register my properties and keep them in sync when the class changes. I would have felt compelled to write a code generator, blech. Adding a new property involves placing a property declaration in the published section of your class. I only suport six property types right now, but it's simple to expand IProperty to any type supported by RTTI. Interface types were next on my list. I've concentrated on the IProperties the most. It seems to work as expected, with few caveats. I've been pleasantly suprised by it. The IObjectList is less developed. I can't make up my mind whether to use a Cursor or an Iterator pattern. I have a small bug in its current implementation of IProperties. An interator would fix that and simplify some subject/observer stuff. The Subject/Obsever stuff is pretty rudimentary. I'm still grappling with it and haven't messed with it in a while. It got tedious writing code to communicate with visual components. I just fixed up a few showstopper bugs so that Paulo could see some code. If you get a chance to look at it any more, comments would be welcome. I'm still not 100% comfortable with interfaces. (ex: how/when/why to use const interface parameters). Don't worry about bruising my ego, this is all a learning exercise for me. My goal has been to include some type of persistent machanism, make it thread safe and build an object server. I got distracted being a soccer coach the last couple of months and I'm helping a friend figure out TCP/IP communications beyond request/response. We want to send out notifications to all the clients when the server processes an update/delete/addition, but that's another thread. -- Iman Back to top Joanna Carter (TeamB) Guest Posted: Sat Dec 11, 2004 1:36 pm    Post subject: Re: ValueType Framework help please "Iman L Crawford" <ilcrawford.at.hotmail.com> a écrit dans le message de news: Xns95BBE6A9A4B6Eilcrwfrd (AT) 207 (DOT) 105.83.66... Quote: Be suprised. If I read the help correctly, forward declared interfaces are no different that forward declared classes. It works without in AV's so far. IMO implementing an interface before its GUID has been declared stops you from casting the an instance of the implementing class to the correct interface. Quote: I didn't want to have to register my properties and keep them in sync when the class changes. I would have felt compelled to write a code generator, blech. Adding a new property involves placing a property declaration in the published section of your class. I only suport six property types right now, but it's simple to expand IProperty to any type supported by RTTI. Interface types were next on my list. The only reason I find for registering Value Types is to cater for OPF mapping or possibly to support knowing which class support which interface. What about having the ability to stream private fields rather than having to access the published properties ? Especially if the property has a different representation to the field . e.g. you might want to store a Date of Birth value but only ever show the Age . Quote: I've concentrated on the IProperties the most. It seems to work as expected, with few caveats. I've been pleasantly suprised by it. I rather like the idea of IProperties; I use a GetValueTypes method on an ObjectValueType to give me an IValueTypeList. Quote: The IObjectList is less developed. I can't make up my mind whether to use a Cursor or an Iterator pattern. I have a small bug in its current implementation of IProperties. An interator would fix that and simplify some subject/observer stuff. To simplify coding, I also use templates in Delphi to allow me to declare a list and an iterator for each type in only half a dozen lines of code. Quote: The Subject/Obsever stuff is pretty rudimentary. I'm still grappling with it and haven't messed with it in a while. It got tedious writing code to communicate with visual components. I just fixed up a few showstopper bugs so that Paulo could see some code. Extending the Observer pattern into the MVP framework really simplified the coding required to get controls hooked up to the VTF (Value Type Framework) Quote: If you get a chance to look at it any more, comments would be welcome. I'm still not 100% comfortable with interfaces. (ex: how/when/why to use const interface parameters). Don't worry about bruising my ego, this is all a learning exercise for me. I am in the middle of evaluating the changes required to port the frameworks to .NET where the interface paradigm is different and we also have garbage collection which tends to obviate the need for some interfaces. Added to which, mixing interfaces and objects is not the problem it is in Delphi for Win32. <Yaaayyy!!> Quote: My goal has been to include some type of persistent machanism, make it thread safe and build an object server. I got distracted being a soccer coach the last couple of months and I'm helping a friend figure out TCP/IP communications beyond request/response. We want to send out notifications to all the clients when the server processes an update/delete/addition, but that's another thread. That really is approaching perfection in OPFs ) Joanna -- Joanna Carter (TeamB) Consultant Software Engineer TeamBUG support for UK-BUG TeamMM support for ModelMaker Back to top Charles McAllister Guest Posted: Sat Dec 11, 2004 3:26 pm    Post subject: Re: ValueType Framework help please Iman L Crawford wrote: Quote: Be suprised. If I read the help correctly, forward declared interfaces are no different that forward declared classes. It works without in AV's so far. you should be aware of this: http://qc.borland.com/wc/wc.exe/details?ReportID=1531 and please vote on it if it becomes a problem for you. Thanks! Back to top Charles McAllister Guest Posted: Sat Dec 11, 2004 3:28 pm    Post subject: Re: ValueType Framework help please Charles McAllister wrote: Quote: you should be aware of this: http://qc.borland.com/wc/wc.exe/details?ReportID=1531 and if you use RTTI, see my comments on this report. Thanks. Back to top Marcos Guest Posted: Sat Dec 11, 2004 3:45 pm    Post subject: Re: ValueType Framework help please Which the importance of "GetMetadata: IMetadata" method inside of TValueType? Could not I simply use the information contained in the inherited interfaces of IValueType (IIntegerValueType, IStringValueType,...) to get all that I want about the attribute? For me, Metadata is information on a class and don't remain an instance of this class. Does anybody have an example of how Metadata of an attribute is used inside of OPF or of MVP? Thank you Back to top Marcos Guest Posted: Sat Dec 11, 2004 4:51 pm    Post subject: Re: ValueType Framework help please Bob Dawson wrote: Quote: Classic metadata for a TStringType, for example, might include Isrequired, min and max length, case sensitivity, case restriction, input mask should a zero-length string be submitted to datastore as is, or as null It is this that I still didn't understand. If I have in a class: TPerson Name: string; Address: string; Both registered like TStringType in a TypeRegister (like Joanna do it). I should have a field metadata (FMetadata: IMetadata) for each attribute (Name and Address) or should I have in both attributes a reference to a single object TStringMetadata? If the affirmative answer is the first one, then I believe that max, length, IsRequired,... they could be put directly in the interface TStringType or your base class (TValueType) and not in an attribute Metadata inside of TStringType. Can anybody comment on? If the affirmative answer is the second one, then max, length, IsRequired could not be part of the metadata because Name.IsRequired attribute can be direferent of Address.IsRequired. Can anybody comment on? Thank you, sry my bad english Back to top Marcos Guest Posted: Sat Dec 11, 2004 5:16 pm    Post subject: Re: ValueType Framework help please Bob Dawson wrote: Quote: Classic metadata for a TStringType, for example, might include Isrequired, min and max length, case sensitivity, case restriction, input mask should a zero-length string be submitted to datastore as is, or as null It is this that I still didn't understand. If I have in a class: TPerson Name: string; Address: string; Both registered like TStringType in a TypeRegister (like Joanna do it). I should have a field metadata (FMetadata: IMetadata) for each attribute (Name and Address) or should I have in both attributes a reference to a single object TStringMetadata? If the affirmative answer is the first one, then I believe that max, length, IsRequired,... they could be put directly in the interface TStringType or your base class (TValueType) and not in an attribute Metadata inside of TStringType. Can anybody comment on? If the affirmative answer is the second one, then max, length, IsRequired could not be part of the metadata because Name.IsRequired attribute can be direferent of Address.IsRequired. Can anybody comment on? 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