Need a variable to persist from database to database?

[G Gabriel]

Re: Need a variable to persist from database to database?

I can't NOT tell whether I'm running DB 1 for the first time (actually I can, because the eval_valid("c_do_what.varname") properly returns false), but when it returns from DB 2, it still returns false.

It shouldn't.
My script says:
if eval_valid(c_do_what.varname)=.f.
The first time, it will be false and the rest of the code will run creating the variable and setting it to "Startup".
However; when you return to DB 1, it will not be false since the variable already exists.
If it returns false, it must be for some other reason.

[jjfcpa]

Re: Need a variable to persist from database to database?

It shouldn't.
My script says:
if eval_valid(c_do_what.varname)=.f.
The first time, it will be false and the rest of the code will run creating the variable and setting it to "Startup".
However; when you return to DB 1, it will not be false since the variable already exists.
If it returns false, it must be for some other reason.

I agree 100%. Here is my code, and it's not working!

if .not. email_valid("c_do_what.varname")
ui_msg_box("BACK IN ALD","Declaring add in variable")
if ui_msg_box("DECLARE","Do you wish to declare add in variable?",UI_QUESTION_SYMBOL + UI_YES_NO) = UI_YES_SELECTED
dim c_do_what as P
c_do_what = addin.variables()
c_do_what.varname = "Startup"
end if
end if

For some reason, it gets inside this "if" statement even when it returns from DB 2.

[G Gabriel]

Re: Need a variable to persist from database to database?

OK John.. it's time for a coffee break!
How did email_valid get in here?

[jjfcpa]

Re: Need a variable to persist from database to database?

OK John.. it's time for a coffee break!
How did email_valid get in here?

You're right... I took a coffee break and came back and tried some other things.

This code is not complicated... at least I don't think so, but the "eval_valid" (sorry about the email_valid, my typo) is not working.

Can I zip up my databases and email them to you? Send me a private msg with email address and I will email to you and you'll see what I mean.

Keep in mind everything works great when I go from db 1 to db 2, it's going back where everything falls apart.

The "eval_valid("c_do_what")" is returning false everytime I come back to db 1. Not good!

[G Gabriel]

Re: Need a variable to persist from database to database?

John:
It's my fault.
You need to enclose the variable in quotations:
should be:

if eval_valid("c_do_what")=.f.
dim c_do_what as P
c_do_what = addin.variables()
c_do_what.varname = "Startup"
end if

I just tested it. It works.

[Lenny Forziati]

Re: Need a variable to persist from database to database?

The correct way to do what you are trying is to always dim c_do_what, your pointer to the addin variables. Then use that pointer to see if the value you are trying to set is there yet:

dim c_do_what as p = addin.variables()
if .not. eval_valid("c_do_what.varname")
    dim c_do_what.varname as c = "Startup"
end if

Alternatively, you can skip the eval_valid() altogether and use the DEFAULT keyword with your dim statement. This will set the value if one isn't already there, but leave any existing value unchanged:

dim c_do_what as p = addin.variables()
dim c_do_what.varname as c = DEFAULT "Startup"

[G Gabriel]

Re: Need a variable to persist from database to database?

Once upon a time, I read the initialization parameter of DIM. Evidently it didn't stick in my head as I didn't envision what to use it for. This is a perfect example.
Nice touch Lenny.

[jjfcpa]

Re: Need a variable to persist from database to database?

The correct way to do what you are trying is to always dim c_do_what, your pointer to the addin variables. Then use that pointer to see if the value you are trying to set is there yet:

dim c_do_what as p = addin.variables()
if .not. eval_valid("c_do_what.varname")
    dim c_do_what.varname as c = "Startup"
end if

Alternatively, you can skip the eval_valid() altogether and use the DEFAULT keyword with your dim statement. This will set the value if one isn't already there, but leave any existing value unchanged:

dim c_do_what as p = addin.variables()
dim c_do_what.varname as c = DEFAULT "Startup"

Lenny

Nicely done. Works perfectly. I hope this code will make it into the V10 help file, because I reviewed it carefully and tried all the code that I could find... to no avail.

Thank you for your help.

For those that are interested, I'm attempting to create a loader database that resides in a public folder. The shortcut installed for the application will always access the loader database and from there it will do a couple of things before loading the application database.

1. It will display a splash screen.

2. It will check an FTP site for updates.

3. If there is a new update, it will download and ask the user if it wants to install the update. If they do, it will update the application database.

After loading the application database, the loader database will be loaded again if they select any of the following options.

1. Move the database to another folder.
2. Backup the database. It will keep track of the backup folder.
3. Restore a backup database.

One of the reasons I decided to do this was because I wanted to be able to gracefully recover if the user attempts to load an application and for one reason or another, the application database is not found. My loader database will handle this by allowing the user to specify a different folder in those cases where the database has been moved or if they have a temporary copy somewhere else that they want to use... say to print reports.

A perfect example of when this will happen is if they have their application database on a network drive and they are not connected to the network (perhaps because they are on a laptop) and away from the office. I do this quite often. I always have a backup copy of the database on my local drive that I access for references purposes (not to make changes), so when I am away from the office, I just use that one instead of the one on the network. The next time I'm connected to the network and startup the application, the database on the network is selected as it should be.

My loader database will handle this without any problem.

Not sure if anyone else has spent any time create a database like this, but I'd be happy to exchange ideas if they have. I will also be happy to share my database loader when I finish it up.

Thanks to Lenny's code, I'm back on track and can see that this will work exactly the way I wanted it to.

Forgot to mention that the loader database will work with any application database with a minimum of changes to the main database.

[G Gabriel]

Re: Need a variable to persist from database to database?

Not really sure why you can't do all these with one DB?
Instead of a "Loader DB", just use a form or an xdlg. Having 2 DB's loaded is a RAM hog and considerably slow especially on a network.
If the object is to be able to work "Offline":
1-That doesn't help much because if you are "viewing only", you might not be viewing the most recent editions.
2-You still can work "Offline" with the single DB if viewing the most recent editions is not an issue and you could also make editions and synch the DB later.

[jjfcpa]

Re: Need a variable to persist from database to database?

Not really sure why you can't do all these with one DB?
Instead of a "Loader DB", just use a form or an xdlg. Having 2 DB's loaded is a RAM hog and considerably slow especially on a network.
If the object is to be able to work "Offline":
1-That doesn't help much because if you are "viewing only", you might not be viewing the most recent editions.
2-You still can work "Offline" with the single DB if viewing the most recent editions is not an issue and you could also make editions and synch the DB later.

Gabriel

AS you can probably tell, I'm still a novice with A5. I've been programming with other db oriented languages for over 25 years, and I'm intrigued by what A5 has to offer. Especially on the web site of things.

As I mentioned, I want to provide a way for my application to gracefully recover from the DB not being available... take the case where the main DB is on a network and is accessed from there normally, but they take their laptop home and try to run the application. With one DB, what would happen in that case if you were running the runtime??? I honestly don't know, but I'm guessing there would be no way to recover without changing the shortcut... not very elegant, especially compared to what we've been offering our clients.

I also think that allowing the user to perform some housekeeping things, like making a copy of the DB, updating the DB after downloading a more current copy of the DB from a website, etc. would best be handled by a housekeeping DB.

And since the housekeeping DB will only be used so infrequently, except for the Startup routine, I don't really see how speed will be an issue.

If you have real experience in this area, I'm all ears.

I really appreciate your contributions to this thread.

[jjfcpa]

Re: Need a variable to persist from database to database?

Gabriel

I forgot to mention that one of the other huge benefits to doing this in a separate database is that it makes it portable across applications.

In the development language that I am coming from, it's possible to create procedure files and reference forms that reside in a separate application. They are compiled in when your application is built. The beauty of this is that these routines - error routine, printing routine, print-to-file routine, backup routine, etc. - can be perfected once and then shared by a host of applications.

This seems to be a real shortcoming of Alpha, and what I'm attempting to do is circumvent this shortcoming in the only way that I know how (right now).