MVP made easier.

[Hansvb]

I will enjoy Easter, Lazarus or mvp have little influence on that. But it might be a good moment to take another good look at everything. I still don't use the full possibilities it seems.

[cdbc]

Hi Hans
Sounds good to me 

I still don't use the full possibilities it seems.

Well in that case, I might just have something to "Wet your appetite" with...
Have you noticed the feature of the TransactionManager:
- It remembers 'Non-Comitted' transactions!

So attached is a small example on how to use / exploit that feature.
It's a small app, I use when I have to publish a project here in the forum, to weed out unwanted files... Nothing fancy 

Happy Easter my friend & have fun...
Regards Benny

edit: The zip now contains all files 

[cdbc]

Sorry mate, forgot these...
They go in 'common'.
Regards Benny

edit: new zip uploaded in previous post, now contains all files

[cdbc]

Helllloooo 
Right, so I had made myself a TODO-list for Easter  ...and today I've finished it,  with a new release of MVP-Setup as the result \o/\ö/\o/  ver.: 14.21.04.2025
Here's an excerpt from the CHANGELOG:

21.04.2025 Added a 'Transaction-Factory' to the transaction-manager, incl. transaction-class'
           registration on unit-initialization. Added a new unit 'common.consts.pas', to do away
           with most of the constant-aliases. Plus added 2 more transaction-examples for you
           guys to play with i.e.: you have to make the view etc. for them - practice )

As always, you can get it HERE at my Gitlab-crib...
Have fun and happy coding out there... 
Regards Benny

[Hansvb]

I start with small steps. I made a simple transaction with the NoRes. That works. It looks like I can put a record that is used in a transaction in model.base or in common.const. Both work but common.const saves 1 alias mentioning.
Then I thought I'd take a look at TFileInfoTrx I have trouble with that. I am doing something wrong in the transaction or in the handling of the Dofunction. If I look at the LSL variable in the transaction, I find 10 files in the list. That is good. But I have no idea how to translate that into the Dofunction. LSL comes in there as a pointer. casting to stringlist gives an empty list. Where am I going wrong?
More questions will come this week if i may .

Code: Pascal  [Select][+][-]

1. procedure TfrmMain.Button1Click(Sender : TObject);
2. var
3.   lTrx: TFileInfoTrx;
4. begin
5.   try
6.     lTrx:= FPresenter.TrxMan.StartTransaction(prFetchFileData) as TFileInfoTrx;
7.     lTrx.Title:= 'd:\Development\Pascal\40\MVP-setup\Gegenereerd_project\Leeg_21042025\';
8.     FPresenter.TrxMan.CommitTransaction;
9.   except
10.     FPresenter.TrxMan.RollbackTransaction;
11.     stbInfo.SimpleText:= 'Oeps';
12.   end;
13. end;  
14.  
15.  
16. { TFileInfoTrx }
17. procedure TFileInfoTrx.Execute(aMgr: ITransactionManager);
18. var lsl: IStringList;
19.   i: Integer;
20.   tmp: String;
21. begin
22.   if fTitle = '' then aMgr.Owner.Provider.NotifySubscribers(prDirDataNeeded,self,nil);
23.   if fTitle = '' then exit;
24.   fDi:= GetDirInfo; { nifty little <experimental> manual interface :o) }
25.   lsl:= fDi.GetFiles(fTitle,true);
26.   // so far ik works. I have to figure out what is happening here.
27.  
28.   // ctrl
29.   i:= lsl.Count;  // = 10 files = good.
30.  
31.   for i:= 0 to lsl.Count -1 do begin
32.     tmp:= lsl[i];  // tmp gets the correct file names = good.
33.   end;
34.  
35.   // nd here i go wrong...
36.  
37. //  aMgr.Owner.Provider.NotifySubscribers(prFetchFileData,self, Pointer(lsl));  // < wrong ??
38. //  aMgr.Owner.Provider.NotifySubscribers(prFetchFileData,self, @lsl);  // < wrong ??
39.   aMgr.Owner.Provider.NotifySubscribers(prFetchFileData,self, lsl);  // < wrong ?? is empty when it arrives in the view ???
40.  
41.   aMgr.Owner.Provider.NotifySubscribers(prStatus,nil,Str2Pch('(i) Dir-Info on "'+Title+'" fetched successfully'));
42. end; { end of examples }

[cdbc]

Hi Hans
This is correct:

Code: Pascal  [Select][+][-]

1. aMgr.Owner.Provider.NotifySubscribers(prFetchFileData,self, lsl);

...and here is one possible way to handle it:

Code: Pascal  [Select][+][-]

1.   case aReason of
2.     { the following line handles the stringlist in userdata/adata }
3.     prDataChanged,prFetchDirData,
4.     prFetchFileData: DoShowText(aNotifyClass,IStringList(aData));
5.     {$ifdef unix}
6.     prDirDataNeeded: TtbdTransaction(aNotifyClass).Title:= InputBox('Dir-Info',
7.                                                                  'Please enter a full path:',
8.                                                                  '/home/bc/src/');
9.     {$endif}
10.     prMainStaticTexts: DoStaticTexts(IStringList(UserData)); { important startup-code }
11.     prStatus: if aNotifyClass = nil then stbInfo.SimpleText:= Pch2Str(UserData)
12.               else DoStatus(aNotifyClass,UserData);
13.   end;

... and finally I stuff it into a memo-control:

Code: Pascal  [Select][+][-]

1. procedure TfrmMain.DoShowText(anObj: TObject; aText: IStrings); { moneygreen: $00AAF0B5 ABGR }
2. var lt: ItbdTransaction; { we use the ancester 'cause we use common title prop }
3. begin
4.   if anObj.GetInterface(ItbdTransaction,lt) then Edit1.Text:= lt.Title;  
5.   aText.AssignToEx(Memo1.Lines); /// into memo here
6. end;

Just remember, it's an IStringlist you're sending, NOT TStringlist.
It works pretty flawless here...
Regards Benny

[cdbc]

Hi
Here's an example view.main.pas/lfm
Regards Benny

[cdbc]

Hi
If you use the example-view, you might miss this function, which I've implemented in 'model.intf.pas':

Code: Pascal  [Select][+][-]

1.  
2. { convenience function for cleaning up CORBA references }
3. procedure FreeCorbaThenNil(var anIntf);
4. { registers sections for use in 'GetStaticTexts()', put it in 'initialization'
5.   at the bottom of the unit, for the objects/units you'll be registering }
6. procedure RegisterSection(const aSect: string);
7. { gets called from model.main.constructor to update the 'Sects' array }
8. procedure UpdateSections(var anArray: TStringArray); // <- - needs 'sysutils' added in top-uses
9.  
10. implementation
11. uses contnrs;
12.  
13. var QSections: TQueue; { storage for our registrations till the model comes online }
14.  
15. procedure FreeCorbaThenNil(var anIntf);
16. begin
17.   if pointer(anIntf) <> nil then begin
18.     IftnCorba(anIntf).Obj.Free;
19.     pointer(anIntf):= nil;
20.   end;
21. end;
22.      

The important one is 'FreeCorbaThenNil();'... 
Regards Benny

[Hansvb]

My DoFiledata was wrong. This works.

Code: Pascal  [Select][+][-]

1. procedure TfrmMain.DoFileData(anObj : TObject; aData : pointer);
2. var
3.   i: Integer;
4.   filelist: IStringList;
5. begin
6.   // just a short test.
7.   filelist:=  IStringList(aData);
8.   if filelist.Count> 0 then begin
9.     Memo1.Clear;
10.     for i:=0 to filelist.Count-1 do begin
11.       memo1.Lines.Add(filelist[i]);
12.     end;
13.   end;
14. end;  

Now I have to understand what I see and what I am doing.

[cdbc]

Hi Hans
Glad you've figured it out...
Btw. there's this method of IStrings, you can use: "procedure AssignToEx(aDest: TStrings;aClearFirst: boolean = true);", so instead of:

Code: Pascal  [Select][+][-]

1. Memo1.Clear;
2.     for i:=0 to filelist.Count-1 do begin
3.       memo1.Lines.Add(filelist[i]);
4.     end;

you can:

Code: Pascal  [Select][+][-]

1. ...
2.   filelist.AssignToEx(memo1.Lines);

-- IStringlist is packed with small conveniences like that... 
I wish you a happy educational journey through the sorce of the new release, don't forget to check out the new Transaction-Factory, hidden in the manager... It should alleviate you having to write lines in the manager's 'StartTransaction' & 'CommitTransaction', respective case statements... 
...As long as you remember to register them on unit initialization...
The 'IDirInfo' interface is for when you're feeling advanced  'cause that's how an interface looks behind the scenes...  Completely made by hand--
Regards Benny

eta: The little interface could serve as a base for a simple "File-Explorer"...

[Hansvb]

don't forget to check out the new Transaction-Factory, hidden in the manager...

I will, but for now i have "problems" with my own tool. I open a second view from view.main and so far that was a simple thing but I now want to create a sqlite file from this view. (I had also circumvented that by putting that in the viewmain). But now I also want to build tables based on Treenodes names. So I guess I should actually provide this view with its own presenter etc to keep things separate. What do you think?

[cdbc]

Hi Hans
Yes, that formally screams for its own Presenter, it's a nifty way of separating module-logic and keep things clean...
I tend to think of it, in the same vein I see TFrames used to group related stuff together and not /clutter/ up the main module...
...Perhaps I would even go so far, as to create a 'model.datastore' along with it, maybe making them children to the 'Main' respectively with a reference...
Sounds good to me, let me know how you fare... 
Regards Benny

eta: Also, as I told you a long time ago, there are mvp'ers out there, who swears by the "1 view->1 presenter->1 model" paradigm...
These paradigms are all dialects of the same basic model, namely the one we practice, just made to scale easier.

[Hansvb]

I think I have almost finished it in an empty project. I have now cut everything up. Custom model and presenter files for the second view. Now I still run into 1 error message that I can't find. "multiple defined symbol "BC_PCH2STR"

Giving a second view my own model, presenter etc seems too much ballast for my simple tool.

[cdbc]

Hi Hans
Look in 'model.decl.pas', there you'll find these:

Code: Pascal  [Select][+][-]

1. { utility functions, here we publicly export these functions, to be made available
2.   in other units, that can't /see/ us, for import :o) gotta love FPC \o/\ö/\o/ }
3. function Pch2Str(aPch: pchar): string; public name 'BC_PCH2STR';
4. function Str2Pch(aStr: string): pchar; public name 'BC_STR2PCH';

Then have a look in 'presenter.trax.pas', where you'll find these:

Code: Pascal  [Select][+][-]

1. implementation
2. // uses StrUtils; { for: 'IndexText' etc... }
3.  
4. { utility functions, taking advantage of the publicly exported functions,
5.   in a unit that we can't /see/ from here. compiler imports for us :o) gotta love FPC }
6. function Pch2Str(aPch: pchar): string; external name 'BC_PCH2STR';
7. function Str2Pch(aStr: string): pchar; external name 'BC_STR2PCH';
8. { the above 2 imports, are here to avoid referencing 'model.decl' in this unit.
9.   if you have to, then only in this 'implementation' part. }      
10.  

The first one publishes the 2 functions and the second one imports them for use...
So I think you have to define 2 of your own, like in presenter.trax, i.e.: the import ones...
Regards Benny

EDIT: OH, I just reread your post, somewhere in your code, you have a second set of the publisher functions... DAS IST VERBOTEN! compiler chokes...  So try to comment the 2 with 'public name' out...

[Hansvb]

Hi Benny,

This works but is wrong. To get rid of the error "multiple defined symbol "BC_PCH2STR", I turned off both functions in model.configure.decl. But then I ran into the fact that they were no longer found. For that I have added model.decl in presenter.configure and in model.configure in the uses. (That's not good, the beginning of spaghetti code). (First mistake). I also run into the fact that I am only allowed to open the second view 1 time. The second time I get stuck on an acces violation in the function:

Code: Pascal  [Select][+][-]

1. unit model.configure.base;
2.  
3. procedure UpdateTransactionManager(aTraxMap: ITraxClassList);
4. begin
5.   TCL.AssignTo(aTraxMap); { everything and the kitchen-sink }  <-- access violation when view is openend for the second time.
6.   TCL:= nil; { release this reference, it's not needed after the manager is up }
7. end;
8.  

It more or less works but I think it's a bit too much of a good thing now.