Best way to exchange data between a form and a unit

[cdbc]

Howdy 
If some of you, are using the mvp-setup, it just got updated to version: 9.21.08.2024 
Features a couple of new factories & methods in 'istrlist' and a refactored 'model.main', to use these. Ofc, it also produces the new stuff...
Regards Benny

[Hansvb]

I already had such a suspicion.I was following this one:

https://forum.lazarus.freepascal.org/index.php/topic,67154.0.html

I'm curious what the consequences are. I had started to revive my stuck app.

[cdbc]

Hi Hans
The 2 new factories (constructors) in play, you can see in 'mvp-setup's 'model.main', here's the constructor:

Code: Pascal  [Select][+][-]

1. constructor TcsuModelMain.Create(aPresenter: IcsuPresenterMain; const aRoot: shortstring);
2. var lfn: string = '';
3. begin
4.   inherited Create;
5.   fPresenter:= aPresenter;
6.   fRoot:= IncludeTrailingPathDelimiter(aRoot);
7.   lfn:= format(csuTexts,[aRoot]);
8.   if FileExists(lfn) then begin { file exists, could be another language, load it! }
9.     { below is the new factory -v- }
10.     fTextCache:= CreStrListFromFile(lfn); ///used to be: CreateStrList; ///
11. ///used to be: fTextCache.LoadFromFile(lfn); ///
12.   end else begin { file doesn't exist, use failsafe in english & try to write it to disk }
13.     fTextCache:= CreStrListFromBytes(file_mvptexts); //<- new factory
14.     try fTextCache.SaveToFile(lfn); except end; { doesn't matter to us if it fails :o) }
15.   end;
16. end;

As you can see, they save me a couple of codelines ~ just sugar 
then have a look at the GetStaticTexts():

Code: Pascal  [Select][+][-]

1. function TcsuModelMain.GetStaticTexts(const aSection: string; out aTarget: integer): IStringList;
2. begin
3.   if aSection = '' then exit(nil);
4.   fSection:= '['+aSection+']'; fSecId:= IndexText(fSection,sects); // iterator-search
5.   if fTextCache.Count = 0 then begin
6.     fPresenter.Provider.NotifySubscribers(prStatus,nil,Str2Pch('(!) ERROR: Could NOT retrieve static texts!'));
7.     exit(nil); /// maybe we should just comment this line and return an empty list, avoid AVs ///
8.   end;
9.   Result:= CreateStrList;
10. ///  fRes:= Result; // tmp placeholder while searching, bug in TStrings-> you cant send userdata along
11.   fTextCache.ForEach(@DoEach,Result);{ iterate over the source-list calling 'doeach' for each item }
12. ///  fRes:= nil;
13.   aTarget:= fSecId; // for the presenter to differentiate between views
14. end;

You can see the difference in the 'ForEach(@DoEach,Result);' call, before I had to keep a tmp(fRes) variable hanging around, just to add to my 'Result' variable in another method, now I just send it along and can use it in the 'DoEach' method. You see below how it's used:

Code: Pascal  [Select][+][-]

1. procedure TcsuModelMain.DoEach(const aValue: string; const anIdx: ptrint;
2.                                anObj: TObject; aData: pointer);
3. var ls: string; lid: integer;
4. begin
5.   if fSecId = -1 then exit;
6.   ls:= LeftWord(aValue);
7.   lid:= IndexText(ls,Sects);
8.   if lid = fSecId then begin
9.     IStringList(aData).Append(aValue); /// <-- HERE typecast(aData)
10.     fInSection:= true;
11.   end else begin
12.     if fInSection then begin
13.       case lid of
14.         0..1: fInSection:= false; /// remember to adjust selector-values according to 'Sects',
15.       end;                        /// the more views = the more selectors, easy-peasy
16.       if fInSection then IStringList(aData).Append(aValue);
17.     end; /////////////// ^------------^ ///// just a simple typecast /////
18.   end;
19. end;

This makes for cleaner code... (when I get around to cleaning it up)
I think this just about explains it. The 'ForEach'es missing 'UserData' param bothered me, so I decided to just implement it. It's all about convenience, you know... 
I don't think they'll have any groundbreaking consequences for you, won't break stuff either 
Regards Benny

[cdbc]

Btw. Hans I think it's cool, that you're reviving your project, sometimes it's just a little detail somewhere, that sheds a whole new light on things...
Have fun with it and if you need anything from me, just holler 
Regards Benny

[Hansvb]

Be careful what you say:

and if you need anything from me, just holler

Yesterday evening I was looking at how to make an app bilingual. I had trouble with the ini file. But don't say anything yet, I still have to get a good look at it. A second file or so.

Added…

I think it's cool, that you're reviving your project

Perhaps. But maybe the idea is not good in the first place. I'm not sure yet. So I'm going for another try. That's the advantage of a bit of hobbies. If it fails, it's not a big deal. At most, a dent in my ego.

[cdbc]

Hi
...uhmmm, I have though it, but I won't say nothing then 
It's quite easy, if you think about it 
Fingers crossed, you'll get it, I'm sure.
Regards Benny

[Hansvb]

I'm not that fast.
You've already done it.

[cdbc]

Hi Hans
Hahaha... sorry mate, to be honest, that was an unfair contest on my side, i18n was part of the reason, I made the GetStaticTexts() the way I did 
Played with the idea all along and it literally took me 20 minutes, to implement the small changes, with double checks and all 
The gui-stuff of managing the lot, I leave to you  right now it just loads the language specified in the 'i18n.cfg' @ startup, proof of concept 
The file 'i18n.cfg' is just because I didn't have an ini-file, the one value could just as easily be read from some existing options/settings -file...
It does show off the new features, quite nicely...
Well, now you've seen it, I hope you don't mind - too much 

Sorry, completely forgot: Have you got any questions?
Regards Benny

[Hansvb]

Sorry, completely forgot: Have you got any questions?

No questions yet. I hope I'll have time over the weekend to take a good look at it. Then a question will probably come up

[Hansvb]

Hi,
I adopted the multilingual into an empty setup I was working on. I have that working now. Now i have to find out how and why it works. But that's what we have the debugger for.

Code: Pascal  [Select][+][-]

1. feaLang:= CreStrListFromFile('i18n.cfg').Values['language'].Trim;

That needs to be a bit more robust. If the file does not exist you will get an access violation. Instead of the file i18n.cfg I can also look at my own settings.cfg file where language already happened to be a key. That's pretty cool.

[cdbc]

Hi Hans
Yeah, I admit that was a 'quickie', but it's just a /placeholder/ for _where_ it has to happen, before the mechanics run their course...  In your 'settings'-file is a better place for it.
A "if Fileexist('i18n.cfg') then ..." would make it robust, because 'feaLang' is a "writable const" a.k.a. "static var" and is already rigged to fallback to 'en' 
I'm happy, it works for you, that means the design is solid and after all, it is an example of how one /might/ go about, solving the 'i18n' task / problem...
I also like that, you can use 'Unitname' and 'Classname' for automatic sectioning, regarding texts in the file 
One thing to contemplate, would be creating a "RegisterSection();" procedure, to take care of /remembering/ to add to the 'Sects' array in 'model.main'...(I think I made a comment about that)... 
Regards Benny

[Hansvb]

I'm trying to understand it and use it in another place. For example, changing the language via a menu choice. I manage to do that, but I don't really understand it enough. I'm coming across too much code that I can't follow. That's going to take a while I'm afraid

What I have done and it works (but I worry if it is not too drastic).

If I change languages, this is immediately visible without having to restart the tool.

Created two menu options. English and Dutch.
Behind English it now says:

Code: Pascal  [Select][+][-]

1.   feaLang:= 'EN';
2.   Presenter:= CreatePresenterMain('');  

And after Dutch it now says:

Code: Pascal  [Select][+][-]

1.   feaLang:= 'NL';
2.   Presenter:= CreatePresenterMain('');  

Re-creating the presenter worries me. I don't think that's the intention

added: found a better way. please wait...

[Hansvb]

This seems like a better way to me. Now the presenter etc. created at start-up remain intact. And switching the language still works immediately when you click in the menu. I am satisfied with this.

Code: Pascal  [Select][+][-]

1. view.main
2. procedure TfrmMain.mmiOptionsLanguageENClick(Sender: TObject);
3. begin
4.   feaLang:= 'EN';
5.   fPresenter.SwitchLanguage(UnitName);
6.   WriteSingleSetting('Language', feaLang);
7. end;     
8.  
9. procedure TfrmMain.mmiOptionsLanguageENClick(Sender: TObject);
10. begin
11.   feaLang:= 'NL';
12.   fPresenter.SwitchLanguage(UnitName);
13.   WriteSingleSetting('Language', feaLang);
14. end;     
15.  
16. presenter.main
17. procedure TPresenterMain.SwitchLanguage(aSection: String);
18. var
19.   ldummy: integer;
20. begin
21.   fModel.SwitchLanguage;
22.   fInternalMsg:= fModel.GetStaticTexts(ClassName,ldummy);
23.   GetStaticTexts(aSection);
24. end;
25.  
26. model.main
27. procedure TModelMain.SwitchLanguage;
28. begin
29.   fTextCache:= CreStrListFromFile(format(mvpTexts,['',feaLang]));
30. end;

[cdbc]

Hi Hans
Nah, recreating the presenter ...that would be *not* so bright, don't do that!
Instead, you could try to implement this in model.main:

Code: Pascal  [Select][+][-]

1. procedure TfeaModelMain.ReloadTextCache;
2. begin
3.   fTextCache.Clear;
4.   fTextCache.LoadFromFile(format(mvpTexts,[fRoot,feaLang]));
5. end;  

And this in presenter.main:

Code: Pascal  [Select][+][-]

1. procedure TfeaPresenterMain.RefreshTextCache(const aSection,aLangStr: string); //=^
2. var
3.   ldummy: integer;
4. begin
5.   feaLang:= trim(aLangStr);
6.   fModel.ReloadTextCache;
7.   fInternalMsg.AssignEx(fModel.GetStaticTexts(ClassName,ldummy)); /// clears first
8.   GetStaticTexts(aSection);
9. end;

...and remember to add them to their respective interfaces..
Then in View area just call:

Code: Pascal  [Select][+][-]

1.  
2. fPresenter.RefreshTextCache(UnitName,'menu-choice');
3.  

That's how I would do it, if it has to be instantaneous and not on restart...
I'm assuming that you've saved the new value to file first. 
Regards Benny
 

[cdbc]

Hahaha...
This time you beat me to it 
Well done =^
It's *so* nice to see, that you've really embraced this way of thinking, your solution shows this clearly, you're looking the right places for solutions 

edit: typo & this is a bit naughty(only work with com intf, else leaks):

Code: Pascal  [Select][+][-]

1. fTextCache:= CreStrListFromFile(format(mvpTexts,['',feaLang]));

You're banking on the compiler free's the old one, ...it does.
The _nicer_ way is to use "AssignEx()" 
Regards Benny