How to save custom variable programmatically?

How to save custom variable programmatically?

[Jean Louis]

I would like to use custom variables in such way to ask user
pragmatically, not through customize interface, to change a
variable. This could be for example user's location.

Upon changing it, I would like programatically to save it for future.

Should I use below function? Or maybe something else is recommended?

(defun customize-save-variable (variable value &optional comment)

  This way it is not working:
  
(require 'cus-edit)
(customize-save hyperscope-default-server "localhost")

Any good way?

Re: How to save custom variable programmatically?

[Robert Pluim]

Jean Louis <bugs@gnu.support> writes:

> I would like to use custom variables in such way to ask user
> pragmatically, not through customize interface, to change a
> variable. This could be for example user's location.
>
> Upon changing it, I would like programatically to save it for future.
>
> Should I use below function? Or maybe something else is recommended?
>
> (defun customize-save-variable (variable value &optional comment)
>

Thatʼs what lots of code in Emacs uses.

>   This way it is not working:
>   
> (require 'cus-edit)
> (customize-save hyperscope-default-server "localhost")

What's not working apart from the fact that customize-save doesnʼt
exist? Or did you mean

(customize-save-variable 'hyperscope-default-server "localhost")

Robert

Re: How to save custom variable programmatically?

[Michael Heerdegen]

Jean Louis <bugs@gnu.support> writes:

> I would like to use custom variables in such way to ask user
> pragmatically, not through customize interface, to change a
> variable. This could be for example user's location.
>
> Upon changing it, I would like programatically to save it for future.
>
> Should I use below function? Or maybe something else is recommended?
>
> (defun customize-save-variable (variable value &optional comment)
>
>   This way it is not working:
>   
> (require 'cus-edit)
> (customize-save hyperscope-default-server "localhost")

(you wanted to typw `customize-save-variable' I guess)

Note that `customize-save-variable' is a function.  Above you pass the
value of a variable instead of a variable: When a function call is
interpreted all arguments are evaluated first.  So you need to quote the
variable name to pass the symbol itself to the function.

Apart from that I think you could use that function.  But do you also
want a prompt for a value?

Michael.

Re: How to save custom variable programmatically?

[Jean Louis]

* Robert Pluim <rpluim@gmail.com> [2020-11-10 13:44]:
> Jean Louis <bugs@gnu.support> writes:
> 
> > I would like to use custom variables in such way to ask user
> > pragmatically, not through customize interface, to change a
> > variable. This could be for example user's location.
> >
> > Upon changing it, I would like programatically to save it for future.
> >
> > Should I use below function? Or maybe something else is recommended?
> >
> > (defun customize-save-variable (variable value &optional comment)
> >
> 
> Thatʼs what lots of code in Emacs uses.
> 
> >   This way it is not working:
> >   
> > (require 'cus-edit)
> > (customize-save hyperscope-default-server "localhost")
> 
> What's not working apart from the fact that customize-save doesnʼt
> exist? Or did you mean
> 
> (customize-save-variable 'hyperscope-default-server "localhost")

Oh that works! Thank you.

Re: How to save custom variable programmatically?

[Jean Louis]

* Michael Heerdegen <michael_heerdegen@web.de> [2020-11-10 14:33]:
> (you wanted to typw `customize-save-variable' I guess)
> 
> Note that `customize-save-variable' is a function.  Above you pass the
> value of a variable instead of a variable: When a function call is
> interpreted all arguments are evaluated first.  So you need to quote the
> variable name to pass the symbol itself to the function.
> 
> Apart from that I think you could use that function.  But do you also
> want a prompt for a value?

That is right, now it works. Yes, I get it with symbols.

I am researching database handling for Emacs and I find it is good to
have those functions. But functions are not written so much in
functional style. It is more in some mixed style.

For example it would be good to have customize-like options to save
any kind of variables in any file, not just into init.el or .emacs as
such are meant more for configuration.

I am now saving into files and reading from files by using these
functions:

(defun string-to-file-force (string file)
  "Prints string into file, matters not if file exists. Returns FILE as file name."
    (with-temp-file file
      (insert string))

(defun file-to-string (file)
  "File to string function"
  (with-temp-buffer
    (insert-file-contents file)
    (buffer-string)))

(defun data-to-file (data file)
  "PRIN1 Emacs Lisp DATA to FILE"
    (string-to-file-force (prin1-to-string data) file))

(defun data-from-file (file)
  "Reads and returns Emacs Lisp data from FILE"
  (car
   (read-from-string
    (file-to-string file))))

The above can be used as rudimentary database of entries for various
applications.

Let us say for invoicing package I am thinking to use various ways of
storing information:

- storing it in ~/.emacs or ~/.emacs/init.el

- storing it in some other files like ~/.emacs.d/data.el

- storing in real databases, such as GDBM, SQL, etc. This complicates
  it. I am thinking that straight GDBM bindings would be best but is
  not in Emacs.
  
If there is anyway of storing data from Emacs that is standard I do
not know about it. Welcoming tips.

Re: How to save custom variable programmatically?

[Michael Heerdegen]

Jean Louis <bugs@gnu.support> writes:

> If there is anyway of storing data from Emacs that is standard I do
> not know about it. Welcoming tips.

The eieio-persistent class is made for that purpose.

You make your data/database/whatever an object of a class you define as
you like, and make that class inherit from eieio-persistent.  Then your
data is savable out of the box.

  (info "(eieio) eieio-persistent")

Do you need an example?

Michael.

RE: How to save custom variable programmatically?

[Drew Adams]

> I would like to use custom variables in such way to ask user
> pragmatically, not through customize interface, to change a
> variable. This could be for example user's location.
> 
> Upon changing it, I would like programatically to save it for future.
> 
> Should I use below function? Or maybe something else is recommended?
> 
> (defun customize-save-variable (variable value &optional comment)
> 
>   This way it is not working:
> 
> (require 'cus-edit)
> (customize-save hyperscope-default-server "localhost")
> 
> Any good way?

Michael has given the answer: `customize-save-variable'.
___

This page has more on the topic of Customize and saving,
if you're interested.  (Just one opinion.)

https://www.emacswiki.org/emacs/CustomizingAndSaving

Re: How to save custom variable programmatically?

[Jean Louis]

* Michael Heerdegen <michael_heerdegen@web.de> [2020-11-10 17:36]:
> Jean Louis <bugs@gnu.support> writes:
> 
> > If there is anyway of storing data from Emacs that is standard I do
> > not know about it. Welcoming tips.
> 
> The eieio-persistent class is made for that purpose.
> 
> You make your data/database/whatever an object of a class you define as
> you like, and make that class inherit from eieio-persistent.  Then your
> data is savable out of the box.
> 
>   (info "(eieio) eieio-persistent")
> 
> Do you need an example?

Thank you. If you have ready simplest example it may be useful for
review.

My strategy is to minimize number of packages used as dependencies so
I try to use what is built in or to re-use what is inside of Emacs.

For simplest database with hundreds of entries file locking and Lisp
data can be enough.

For larger database I would prefer GDBM bindings built-in, but life is
not a dream.

Personally I am using PostgreSQL. Then I just define the table
definition and that may be similar to eieio.

Re: How to save custom variable programmatically?

[Jean Louis]

* Drew Adams <drew.adams@oracle.com> [2020-11-10 19:25]:
> > I would like to use custom variables in such way to ask user
> > pragmatically, not through customize interface, to change a
> > variable. This could be for example user's location.
> > 
> > Upon changing it, I would like programatically to save it for future.
> > 
> > Should I use below function? Or maybe something else is recommended?
> > 
> > (defun customize-save-variable (variable value &optional comment)
> > 
> >   This way it is not working:
> > 
> > (require 'cus-edit)
> > (customize-save hyperscope-default-server "localhost")
> > 
> > Any good way?
> 
> Michael has given the answer: `customize-save-variable'.
> ___
> 
> This page has more on the topic of Customize and saving,
> if you're interested.  (Just one opinion.)
> 
> https://www.emacswiki.org/emacs/CustomizingAndSaving

Thank you for reference. I was looking into it for reason to enable
those functions to save to other files. Instead customization of Emacs
to use it to save any variables like a simple database in different
files.

Re: How to save custom variable programmatically?

[Marcin Borkowski]

On 2020-11-10, at 20:19, Jean Louis <bugs@gnu.support> wrote:

> * Michael Heerdegen <michael_heerdegen@web.de> [2020-11-10 17:36]:
>> Jean Louis <bugs@gnu.support> writes:
>> 
>> > If there is anyway of storing data from Emacs that is standard I do
>> > not know about it. Welcoming tips.
>> 
>> The eieio-persistent class is made for that purpose.
>> 
>> You make your data/database/whatever an object of a class you define as
>> you like, and make that class inherit from eieio-persistent.  Then your
>> data is savable out of the box.
>> 
>>   (info "(eieio) eieio-persistent")
>> 
>> Do you need an example?
>
> Thank you. If you have ready simplest example it may be useful for
> review.
>
> My strategy is to minimize number of packages used as dependencies so
> I try to use what is built in or to re-use what is inside of Emacs.

You might get inspired by an old post of mine here:
http://mbork.pl/2018-09-10_Persisting_Emacs_variables

Best,

-- 
Marcin Borkowski
http://mbork.pl

Re: How to save custom variable programmatically?

[Michael Heerdegen]

Jean Louis <bugs@gnu.support> writes:

> My strategy is to minimize number of packages used as dependencies so
> I try to use what is built in or to re-use what is inside of Emacs.

Eieio is part of Emacs.  The Gnus registry is saved using
eieio-persistent.

This class is relatively new and was a bit buggy in the past, though.
In new Emacs versions it works reliably AFAICT.

> Personally I am using PostgreSQL. Then I just define the table
> definition and that may be similar to eieio.

Might also be interesting.

The Eieio approach has the advantage that (an) Emacs Lisp (object) is
saved as (an) Emacs Lisp (expression).  It is slow, however.


Michael.

Re: How to save custom variable programmatically?

[Michael Heerdegen]

Jean Louis <bugs@gnu.support> writes:

> Thank you. If you have ready simplest example it may be useful for
> review.

Simplest?  Ok, that might be possible.  Let's make a wrapper holding a
single value that is savable:

#+begin_src emacs-lisp
  (defclass my-persistent (eieio-persistent)
    ((data :initarg :data)))

  (defun my-save-in-location (thing file)
    (let ((obj (my-persistent :data thing)))
      (setf (oref obj file) file)
      (eieio-persistent-save obj)))

  ;; save a value to a file:
  (my-save-in-location (list 'x [] "Hello")
                       (expand-file-name "~/test"))

  ;; get it back:
  (oref (eieio-persistent-read
         (expand-file-name "~/test")
         'my-persistent)
        :data)
  ;; ==> (x [] "Hello")
#+end_src

This is not only a nice abstraction.  eieio-persistent has some
(programmable) knowledge about how to print and "restore" objects where
a normal print+read cycle would not work.

Michael.

Re: How to save custom variable programmatically?

[Jean Louis]

* Marcin Borkowski <mbork@mbork.pl> [2020-11-10 23:42]:
> 
> On 2020-11-10, at 20:19, Jean Louis <bugs@gnu.support> wrote:
> 
> > * Michael Heerdegen <michael_heerdegen@web.de> [2020-11-10 17:36]:
> >> Jean Louis <bugs@gnu.support> writes:
> >> 
> >> > If there is anyway of storing data from Emacs that is standard I do
> >> > not know about it. Welcoming tips.
> >> 
> >> The eieio-persistent class is made for that purpose.
> >> 
> >> You make your data/database/whatever an object of a class you define as
> >> you like, and make that class inherit from eieio-persistent.  Then your
> >> data is savable out of the box.
> >> 
> >>   (info "(eieio) eieio-persistent")
> >> 
> >> Do you need an example?
> >
> > Thank you. If you have ready simplest example it may be useful for
> > review.
> >
> > My strategy is to minimize number of packages used as dependencies so
> > I try to use what is built in or to re-use what is inside of Emacs.
> 
> You might get inspired by an old post of mine here:
> http://mbork.pl/2018-09-10_Persisting_Emacs_variables

Nice post and Wiki. Reference taken. I can read the flow somehow. You
watching in the file by trying to read ^(setq if variable exists, if I
get it well. It relies on personal use case and common usage of
setq. What if variable is b that is set with:

(set (quote b) 1)

or

(setq a 1 b 2)

or

(setq a 1
      b 2
      c 3)

or

(setf b 1)

For me personally I save major information in the database. But to
make simpler package for users to do one thing do well I like to find
solutions that is preferrably built-in and well proven.

Re: How to save custom variable programmatically?

[Jean Louis]

* Michael Heerdegen <michael_heerdegen@web.de> [2020-11-10 23:44]:
> Jean Louis <bugs@gnu.support> writes:
> 
> > My strategy is to minimize number of packages used as dependencies so
> > I try to use what is built in or to re-use what is inside of
> > Emacs.

Thank you, I see it now. It is similar to CLOS. Which I never well
understood, maybe in future.

> The Eieio approach has the advantage that (an) Emacs Lisp (object) is
> saved as (an) Emacs Lisp (expression).  It is slow, however.

Do you have example for:

- client's name (to be key for below)
  - address line 1
  - address line 2
  - address line 3
  - postal code
  - city
  - country
  - phone
  - fax
  - mobile
  - email

Re: How to save custom variable programmatically?

[Jean Louis]

* Michael Heerdegen <michael_heerdegen@web.de> [2020-11-11 00:17]:
> Jean Louis <bugs@gnu.support> writes:
> 
> > Thank you. If you have ready simplest example it may be useful for
> > review.
> 
> Simplest?  Ok, that might be possible.  Let's make a wrapper holding a
> single value that is savable:
> 
#+begin_src emacs-lisp
  (defclass my-persistent (eieio-persistent)
    ((data :initarg :data)))

I got:

eieio-defclass-internal: Given parent class eieio-persistent is not a
classInvalid face reference: mail-double-quoted-text-face (this last
one is maybe not related)

I understand it works on your side, not yet on mine, I wish to
understand it.

Re: How to save custom variable programmatically?

[Michael Heerdegen]

Jean Louis <bugs@gnu.support> writes:

> #+begin_src emacs-lisp
>   (defclass my-persistent (eieio-persistent)
>     ((data :initarg :data)))
>
> I got:
>
> eieio-defclass-internal: Given parent class eieio-persistent is not a
> class

Sorry, I didn't check what you should `require'.  I also didn't check
now, but with the following the definition works for me in emacs -Q:

  (require 'eieio)
  (require 'eieio-base)


Michael.

Re: How to save custom variable programmatically?

[Michael Heerdegen]

Jean Louis <bugs@gnu.support> writes:

> Do you have example for:
>
> - client's name (to be key for below)
>   - address line 1
>   - address line 2
>   - address line 3
>   - postal code
>   - city
>   - country
>   - phone
>   - fax
>   - mobile
>   - email

Hey! - I finally recognize fishing emails when I see them!

Ok, jokes aside, but isn't

  (info "(eieio) Quick Start")

giving an example just like that?

Then all you have to do is to collect your records (your objects) in a
data structure, e.g. a hash table (with names as the keys), which is an
object of a class similar to what I had posted, simply inheriting from
eieio-persistent, and that's it.

HTH,

Michael.

Re: How to save custom variable programmatically?

[Jean Louis]

* Michael Heerdegen <michael_heerdegen@web.de> [2020-11-11 21:01]:
> Jean Louis <bugs@gnu.support> writes:
> 
> > Do you have example for:
> >
> > - client's name (to be key for below)
> >   - address line 1
> >   - address line 2
> >   - address line 3
> >   - postal code
> >   - city
> >   - country
> >   - phone
> >   - fax
> >   - mobile
> >   - email
> 
> Hey! - I finally recognize fishing emails when I see them!
> 
> Ok, jokes aside, but isn't
> 
>   (info "(eieio) Quick Start")
> 
> giving an example just like that?
> 
> Then all you have to do is to collect your records (your objects) in a
> data structure, e.g. a hash table (with names as the keys), which is an
> object of a class similar to what I had posted, simply inheriting from
> eieio-persistent, and that's it.

Thank you for reference, I will come to that.

Re: How to save custom variable programmatically?

[Marcin Borkowski]

On 2020-11-10, at 22:46, Jean Louis <bugs@gnu.support> wrote:

> * Marcin Borkowski <mbork@mbork.pl> [2020-11-10 23:42]:
>> 
>> On 2020-11-10, at 20:19, Jean Louis <bugs@gnu.support> wrote:
>> 
>> > * Michael Heerdegen <michael_heerdegen@web.de> [2020-11-10 17:36]:
>> >> Jean Louis <bugs@gnu.support> writes:
>> >> 
>> >> > If there is anyway of storing data from Emacs that is standard I do
>> >> > not know about it. Welcoming tips.
>> >> 
>> >> The eieio-persistent class is made for that purpose.
>> >> 
>> >> You make your data/database/whatever an object of a class you define as
>> >> you like, and make that class inherit from eieio-persistent.  Then your
>> >> data is savable out of the box.
>> >> 
>> >>   (info "(eieio) eieio-persistent")
>> >> 
>> >> Do you need an example?
>> >
>> > Thank you. If you have ready simplest example it may be useful for
>> > review.
>> >
>> > My strategy is to minimize number of packages used as dependencies so
>> > I try to use what is built in or to re-use what is inside of Emacs.
>> 
>> You might get inspired by an old post of mine here:
>> http://mbork.pl/2018-09-10_Persisting_Emacs_variables
>
> Nice post and Wiki. Reference taken. I can read the flow somehow. You
> watching in the file by trying to read ^(setq if variable exists, if I
> get it well. It relies on personal use case and common usage of
> setq. What if variable is b that is set with:
>
> (set (quote b) 1)
>
> or
>
> (setq a 1 b 2)
>
> or
>
> (setq a 1
>       b 2
>       c 3)
>
> or
>
> (setf b 1)

Well, it won't work;-).  The idea is, though, that this line is put in
init.el automatically and not tampered manually.

Best,

-- 
Marcin Borkowski
http://mbork.pl

Re: How to save custom variable programmatically?

[Michael Heerdegen]

Jean Louis <bugs@gnu.support> writes:

> Do you have example for:
>
> - client's name (to be key for below)
>   - address line 1
>   - address line 2
>   - address line 3
>   - postal code
>   - city
>   - country
>   - phone
>   - fax
>   - mobile
>   - email

BTW, if you actually happen to want to have a database of contacts, I
have to add that there are special solutions for that task of course:
BBDB, its successor EDBD, and org-contacts (I currently use the first
one; there may be more).

Michael.

Re: How to save custom variable programmatically?

[Jean Louis]

* Michael Heerdegen <michael_heerdegen@web.de> [2020-11-17 15:24]:
> Jean Louis <bugs@gnu.support> writes:
> 
> > Do you have example for:
> >
> > - client's name (to be key for below)
> >   - address line 1
> >   - address line 2
> >   - address line 3
> >   - postal code
> >   - city
> >   - country
> >   - phone
> >   - fax
> >   - mobile
> >   - email
> 
> BTW, if you actually happen to want to have a database of contacts, I
> have to add that there are special solutions for that task of course:
> BBDB, its successor EDBD, and org-contacts (I currently use the first
> one; there may be more).

Question for the structure is meant for packages that produce invoices
and quotations for customers where user does not need any outside
package or anything more sophisticated. Just entering few tables, few
items or articles or goods, pricing and creating invoice.

For contacts management I will have new package for GNU ELPA, it will
come. I am using it since quite some time for me and it comes from CRM
or Customer Relationship Management database and different web GUI.

GeDaFe - PostgreSQL Generic Database Interface
==============================================
Hyperlink: http://gedafe.github.io/doc/gedafe-sql.en.html 

Gedafe is a generic web front-end to PostgreSQL. Generic means in this
context that Gedafe does not know anything about the structure or
contents of the database it is presenting.

Over many years using Gedafe interface I have developed many various
PostgreSQL tables for various use cases. Let us say for mapping lands
and generation of maps or for planning, invoices, etc.

Contacts are of course included together with various accounts and
integrations that is way complex than BBDB. For me personally I have
contacts management that satisfied all personal needs (not public
need).

For a package to create invoices and to be very simple as Emacs is
simple for the user, I am looking how to structure data and save it
for the user.

I think that packages should support various databases:

1. Emacs based databases should be simplest

2. GDBM database, I hope to sponsor dynamic module for GDBM soon,

3. PostgreSQL, dynamic module already exists

For the option 3. I have the solution and `emacs-libpq` will come soon
to GNU ELPA: https://github.com/anse1/emacs-libpq.git

For option 1. I look for solution to make it simple for those users
who do not have many clients and do not need sophisticated database in
background.

Option 3. with GDBM will come in future and I hope it will enhance
Emacs as programming interface to databases.

So structure with EIEIO will serve for option 1.

Jean

Re: How to save custom variable programmatically?

[Jean Louis]

* Michael Heerdegen <michael_heerdegen@web.de> [2020-11-11 00:17]:
> Jean Louis <bugs@gnu.support> writes:
> 
> > Thank you. If you have ready simplest example it may be useful for
> > review.
> 
> Simplest?  Ok, that might be possible.  Let's make a wrapper holding a
> single value that is savable:
> 
> #+begin_src emacs-lisp
>   (defclass my-persistent (eieio-persistent)
>     ((data :initarg :data)))
> 
>   (defun my-save-in-location (thing file)
>     (let ((obj (my-persistent :data thing)))
>       (setf (oref obj file) file)
>       (eieio-persistent-save obj)))

> This is not only a nice abstraction.  eieio-persistent has some
> (programmable) knowledge about how to print and "restore" objects where
> a normal print+read cycle would not work.
> 
> Michael.

I remember from Common Lisp about `defstruc' and more than that I did
not use. But I remember `defstruct' preparing various methods
(probably methods) automatically. From there I understand this and
keep it as note until I come to implement it.

As it is built-in, it offers straight solution, good to know!

Jean

Re: How to save custom variable programmatically?

[Michael Heerdegen]

Jean Louis <bugs@gnu.support> writes:

> I remember from Common Lisp about `defstruc' and more than that I did
> not use. But I remember `defstruct' preparing various methods
> (probably methods) automatically.

For the sake of completeness: In Emacs Lisp we also have structs via
`cl-defstruct'.  These are not part of EIEIO (though EIEIO knows how to
handle them).  Accessors, constructors etc are ordinary functions and
macros.

Independent of EIEIO and structs Emacs Lisp has also generic functions
and methods.

Michael.

Re: How to save custom variable programmatically?

[Stefan Monnier]

>> I remember from Common Lisp about `defstruc' and more than that I did
>> not use. But I remember `defstruct' preparing various methods
>> (probably methods) automatically.
> For the sake of completeness: In Emacs Lisp we also have structs via
> `cl-defstruct'.  These are not part of EIEIO (though EIEIO knows how to
> handle them).

I think you mean Emacs's generic functions know how to handle them.
EIEIO's old generic functions didn't, and the rest of EIEIO is specific
to `defclass`.


        Stefan