[DUG] Runtime user defined fields

[russell]

Rohit's method is like one I use that allows users to "add fields".

 

Users add records to an existing table. The program manages these records
(so it appears to users) as if they are fields.

The field types are important if you allow users to store data that will not
fit into a fixed length field. 

 

I allow three data types: Text, FileNames and Memo. The first two are single
lines of text of any length and the third handles multi-line data.

All three types are stored as BLOBs in a Firebird db file.

 

A "con" is these fields are not easily searched . but I do not need this
ability.

 

Best regards,

Russell

 

From: delphi-bounces at listserver.123.net.nz
[mailto:delphi-bounces at listserver.123.net.nz] On Behalf Of Rohit Gupta
Sent: Wednesday, 6 March 2013 11:49 a.m.
To: NZ Borland Developers Group - Delphi List
Cc: List NZ Borland Developers Group - Delphi
Subject: Re: [DUG] Runtime user defined fields

 

I would consider having a generic table where you soft-add the fields

Ref_Num : autoinc
Owner_Num : int64
Field_Name : string (16)
Field_Type : integer // ord(TFieldType)
Field_Data  : string (255)  // store everything as string but the type above
tells you what it is

This way you dont alter the database.  You dont have to worry about indexes
etc.  Everyones database is the same.  Yet you can search for data for a
particular field name.  I am actually using this structure in a three
projects.

Regards

Rohit

On 6/03/2013 10:41 a.m., Steve Peacocke wrote:

Hi everyone,
 
I've been away from programming for a while so please excuse the
seemingly simple question.
 
I'm designing a user interface for a new application and wondered if
there was a generally accepted way that this "should" be done.
 
The application will allow end users to edit their forms allowing them
to add, move, and remove fields at runtime. I'm using MySQL but I was
wondering if there was an accepted way of adding and changing fields
to a database.
 
I know I can use SQL for this but I also don't want to make every
application unable to be managed or upgraded. Perhaps I can ensure
that the 3-4 permanent fields are never able to be altered (ID, Name,
etc) but allow the user (through a suitable user-friendly interface)
to go crazy adding such fields as My_favourite_colour, Rating,
Priority, Notes, etc. etc.
 
I'm able to give a suitable user-friendly interface to allow them to
physically alter the Delphi form at runtime, but wondered about the
"most appropriate way" to modify the fields to the database.
 
1. I could simply add fields using SQL's ALTER TABLE
2. I could add another table with fields such as TableName, FieldName,
Type, etc.. and add to that
3. Some other spiffy way that you people will suggest that I haven't
even thought of yet.
 
Any suggestions?
 
 
Steve Peacocke
+64 220 612-611
http://www.nzorient.co.nz
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-- 
Regards

Rohit Gupta
B.E. Elec., M.E., Mem IEEE, Member IET
Technical Director
Computer Fanatics Ltd

Tel 4892280 
Fax 4892290 
Web www.cfl.co.nz

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