Question

Dynamic form not displaying query

Asked by: OrionPMS

I have a dynamically created form, which displays multiple controls linked to a TQuery which is opened prior to the form being created.  Everything works fine for the first time the form is displayed, but on the second or subsequent displays of the form, no data is shown!  The Query is closed after each form display, and then the form is freed but then each is recreated the second time exactly as the first but without success.  The form being opened has nil as the creator.  The operation of the Tquery is perfect the first time, with edits being successful etc.  Second time, all controls are blank!

The dynamic form shows fields which are linked to a datasource, which itself is a detail table of the main table on the static main form... eg, master record is a client record, itself the result of a Tquery, the detail table which is giving the problems contains assessment records for that client.  The linking field is a simple unique serial number, from an integer field. We do not use Delphi Mastersource/Field at all.

My question is why should the dynamic form not display the Tquery results the second time?

This Question has been solved and asker verified All Experts Exchange premium technology solutions are available to subscription members.

Subscribe now for full access to Experts Exchange and get

Instant Access to this Solution

  • Plus...
  • 30 Day FREE access, no risk, no obligation
  • Collaborate with the world's top tech experts
  • Unlimited access to our exclusive solution database
  • Never be left without tech help again

Subscribe Now

Asked On
2005-08-20 at 08:40:36ID21533979
Tags

delphi

,

dynamic

,

form

,

query

Topic

Delphi Programming

Participating Experts
1
Points
500
Comments
11

Trusted by hundreds of thousands everyday for fast, accurate and reliable tech support.

  • "The time we save is the biggest benefit of Experts Exchange to Warner Bros. What could take multiple guys 2 hours or more each to find is accessed in around 15 minutes on Experts Exchange." Mike Kapnisakis, Warner Bros.
  • "Our team likes having a resource that is more secure than just using Google and most experts using this service really know their stuff. It's nice to look here first versus using Google." Dayna Sellner, Lockheed Martin
  • "Anytime that I've been stumped with a problem, 9 out of 10 times Experts Exchange has either the accepted solution or an open discussion of the potential solution to the problem." Kenny Red, eBay Inc.

See what Experts Exchange can do for you.

Got a question?

We've got the answer.

Experts Exchange has been collecting answers to technology questions since 1996…3 million and counting! If you have a question, chances are we already have your answer.

Screenshot of Experts Exchange Knowledgebase

Need individual assistance?

Our experts are ready to help.

If you can't find the exact answer you're looking for, ask our exclusive community of 50,000 experts. You’ll get a personalized answer from a trusted professional.

Screenshot of Experts Exchange Knowledgebase

Want to learn from the best?

Read articles from industry experts.

Thousands of free tech tips, tricks, how-to’s and tutorials are available in our peer reviewed articles section. See for yourself how smart our experts are, no login required.

Screenshot of an Article

Working on a long term project?

Store your work and research.

Save solutions to your questions, answers you’ve discovered through searching plus helpful articles in your personal knowledgebase for easy future access.

Screenshot of Experts Exchange Knowledgebase

Access the answers to your technology questions today.

Subscribe Now

30-day free trial. Register in 60 seconds.

What Makes Experts Exchange Unique?

Members of the expert community talk about why the experience at Experts Exchange is different than what you will find anywhere else.

Trusted by the world's most respected brands.

image of each brand's logo

Faithfully serving IT professionals since 1996.

Experts Exchange Logo

Try it out and discover for yourself.

Subscribe Now

30-day free trial. Register in 60 seconds.

Related Solutions

  1. FieldByName(...).AsBoolean := nil ?
    I am puzzled as to how to set a field value in a Paradox table to NIL. Yes, I can set a Boolean field to either True or False, but how does one set the field to NIL/empty? IOW, how do you set it back to its original, virgin, unedited state? This does not work... frmMain....
  2. Setting to Nil
    Can someone please tell me if it is one hundred percent necessary to set an object to nil after freeing it? What are the advantages disadvantages?? ie MyObject.Free; MyOject := nil;
  3. How to set Query's property DataSource with null source?
    I set Query's Property DataSource for linking to Master Table, such as: Query1.DataSource:=DataSource1. But in running time, sometimes I want Query1 working independing. Therefore I have to release this Master/Detail relation. I wrote Query1.DataSource:='', and got compiler e...
  4. Dynamic Forms Creator - Mysql as backend
    Hi , Ive designed a corporate Intranet in VBScript/HTML/Javascript on asp using mysql as DB backend.. I have many requests to create forms for users for a variety of tasks... Forms for Travel requests , Expenses requests etc... What Id like to do is create some kind of dyna...
  5. Why is FieldAddress nil
    Delphi 7. Create a new Application and place a Button on a Form. Double-click on the Button to enter the following code on the OnClick event: // start if Button1.FieldAddress('Caption') <> nil then ShowMessage('You solved this problem!'); // end Compile, run, and ...
  6. AV on Statusbar nil
    Hi expert, I cannot always reproduce this problem, but now that it occurs I might as well describe it and ask you if you know an answer. Problem is, that I get an Access Violence message on the Statusbar being nil in the following Procedure TNotePrp.ShowHint(Sender: TObjec...

Free Tech Articles

  1. WARNING: 5 Reasons why you should NEVER fix a computer for free.
    It is in our nature to love the puzzle. We are obsessed. The lot of us. We love puzzles. We love the challenge. We thrive on finding the answer. We hate disarray. It bothers us deep in our soul. W...
  2. SCCM OSD Basic troubleshooting
    SCCM 2007 OSD is a fantastic way to deploy operating systems, however, like most things SCCM issues can sometimes be difficult to resolve due to the sheer volume of logs to sift through and the dispe...
  3. Migrate Small Business Server 2003 to Exchange 2010 and Windows 2008 R2
    This guide is intended to provide step by step instructions on how to migrate from Small Business Server 2003 to Windows 2008 R2 with Exchange 2010. For this migration to work you will need the fo...
  4. Create a Win7 Gadget
    This article shows you how to create a simple "Gadget" -- a sort of mini-application supported by Windows 7 and Vista. Gadgets can be dropped anywhere on the desktop to provide instant information, ...
  5. Outlook continually prompting for username and password
    There have been a lot of questions recently regarding Outlook prompting for a username and password whilst using Exchange 2007. There are a few reasons why this would happen and I will try to cover t...
  6. Backup Exchange 2010 Information Store using Windows Backup
    There seems to be quite a lot of confusion around the ability to backup Exchange 2010 using the built in Windows Backup feature. This stems from the omission of this feature prior to Exchange 2007 s...

Cloud Class Webinars

  1. Avoiding Bugs in Microsoft Access
    Alison Balter takes and in-depth look at avoiding bugs in Access. In this webinar you will learn about using the immediate window to debug your applications, invoking the debugger, using breakpoints to troubleshoot, stepping through code, setting the next statement to execute, ...
  2. Top 10 Best New Features in Visio 2010
    Scott Helmers gives live demonstrations of the top 10 new features in Visio 2010. This webinar will teach you how to create compelling diagrams by adding shapes to the page with a single click, linking the shapes in a diagram to data in Excel (or SQL Server, or SharePoint), ...
  3. IT Consultant Business Secrets Revealed
    Michael Munger, Experts Exchange tech pro and IT consultant, pulls back the curtain on his very successful businesses and answers question on every IT consultant and business owner should know about. He shares secrets on what he did to solve the 5 most common problems in IT, ...
  4. Disaster Recovery and Business Continuity
    Quest CTO, Mike Billon, gives an overview of the steps involved in building a dunamic disaster recovery plan. Through case studies and an examination of software/hardware tooles for monitoring and testing, you'll gain a better understandin of where you are, where you want ...
  5. Organize Your Visio Diagrams with Containers and Lists
    Scott Helmers uses cross functional flowcharts, wireframe diagrams, data graphic legends and seating charts to teach you: how to ustilize all three new structured diagram components in Visio 2010, the best practices for organizeing shapes in previous version of Visio, how to organize ...
  6. How to Us Objects, Properties, Events and Methods in Microsoft Access
    Alison Dalter gives an in-depbth look at objects, properties, events and methods in Microsoft Access. In this webinar you will learn about using the object browser, referring to objects, working with properties and methods, working with object variables, understanding the ...

Join the Community

Give a Little. Get a Lot.

Join the community of experts here and help other tech pros by answering question in your area of expertise. You can earn FREE access to all Experts Exchange's premium features and resources.

Join the Community

Answers

 

by: RadikalQ3Posted on 2005-08-20 at 09:03:47ID: 14715947

Hi!

I think that the key is in: "multiple controls linked to a TQuery which is opened prior to the form being created"

I think that when your form is closed/destroyed the TQuery is not leaved as the first time that the form is created.

Try to incorporate the logic for initialize the TQuery into the form...

 

by: OrionPMSPosted on 2005-08-20 at 09:12:26ID: 14715973

>>Try to incorporate the logic for initialize the TQuery into the form...

I would be happy to do so but.....

Our process on every occasion is as follows:

1.  Set SQL parameters and SQL in code.
2.  Create and open detail form.
3. When form is closed, close query from within master form.
4. Destroy detail form.

If the detail form is re-created each time, should the same conditions not exist each time? Does closing the query while the detail form is alive make permanent run time changes to that form?

 

by: RadikalQ3Posted on 2005-08-20 at 09:24:21ID: 14716009

Maybe when you close the detail form, you are making (unspected) changes in the master form (and in the Query of the master form).
For debug process. you can make the same process but without creating/destroying the form... just showit and hideit.

 

by: OrionPMSPosted on 2005-08-20 at 09:49:53ID: 14716065

Tried putting the query creation code in the OnCreate event of the sub form, and the query closing code in the OnClose event but same problem.

Ive also tried not closing the query on the sub form being closed, since it doesnt matter if its closed or not, but that doesnt help either.

Now tried to have a static sub form, whereby its created at application launch time, but same problem.  It has to be a TQuery problem somehow, but surely not a unique problem.  I imagine people would want to show a queried sub form for a great many applications, but how is it done?

 

by: OrionPMSPosted on 2005-08-20 at 09:51:03ID: 14716073

The query of the master form isnt affected... it works fine.  There is a reference to the master record within the sub form and it displays the correct serial number each time... but still on the second display, all the controls are blank.

 

by: RadikalQ3Posted on 2005-08-20 at 09:53:13ID: 14716080

Normally, the data components are placed into an static (and globally accesed) DataModule, and the details forms are created in runtime, accessing to the datasets placed into the datamodule.

 

by: RadikalQ3Posted on 2005-08-20 at 09:54:20ID: 14716084

The query is ready, but... the datasource is also ready?

 

by: OrionPMSPosted on 2005-08-20 at 09:56:16ID: 14716087

Yes... we have a globally accessed Datamodule, which houses the relevant dataset components.  The master database connection component (we use Advantage incidentally) opens the database and everything happens after that... we have used this database for many years without a problem, but this is the first time we have had a need to use a process such as this.

 

by: OrionPMSPosted on 2005-08-20 at 10:43:38ID: 14716244

In the datamodule there is a TQuery and a TDatasource component.  The relevant properties are filled in.  The SQL property for the TQuery is blank, since this is set at runtime.  The TDatasource refers to the TQuery component.  The TQuery expects a live cursor and the TDatasourc has the Enabled property set to True.  There appears to be no problem with these components.

 

by: RadikalQ3Posted on 2005-08-20 at 12:43:50ID: 14716618

I have made any test...

Test with this for the detail query prior to show the detail form:

  Query1.Close;  //Close is open in designtime
  if NOT Query1.Prepared then query1.Prepare;
  Query1.Open;

 

by: OrionPMSPosted on 2005-08-21 at 07:40:47ID: 14718993

I got it to work... seems that parameters were to blame.  On the query for the 'master' table I had used a string parameter and that works fine, but the 'detail' table has an integer parameter.  I had the type selected correctly but still the parameter did not display the SQL result properly on the second time.

This doesnt work:  'SELECT * FROM TRIAGE WHERE SERIAL = :P_SERIAL'

But this does:  'SELECT * FROM TRIAGE WHERE SERIAL = ' + IntToStr(v_serial)

v_serial is an integer variable with the value of the master table key field.

I tried the Prepare syntax you suggest and it does not stop the system from working, so not sure if it is necessary.

Ironically I tried the above SQL syntax with the master string query and it doesnt work!!  I think I have the string handling wrong for that.  

BUT... I also made the detail form a static form, created once at program launch.  I dont think that contributed to the above syntax working.

20120131-EE-VQP-002

3 Ways to Join

30-Day Free Trial

The Experts

98% positive feedback on 31,087 answers since March 2000. angeliii is a Microsoft Most Valuable Professional for his work with MS SQL Server & Develoment.

He has also proven his knowledge of Visual Basic Programming, PHP Scripting and Oracle Databases.

The Experts

97% positive feedback on 10,752 answers since July 2000. lrmoore has more than 18 years experience in the networking industry.

The six-time Mircosoft MVPs specialties include firewalls, virtual private networking, and network management.

Testimonials

"...and excellent source for support... Kind of like having your very own IT dept." Electriciansnet

Testimonials

"I was apprehensive at signing up at first. However... it has already made my life as an IT administrator much easier." JaCrews

Testimonials

"WOW! You guys have great, active, and knowledgeable people on here." moore50

Business Clients

Business Clients

In the Press

"If you’ve got a question... Experts Exchange can supply an answer.”

In the Press

"...an invaluable aid for both IT professionals and those who require tech support."

In the Press

"where IT professionals provide quick answers on just about any topic"

Business Account Plans

Loading Advertisement...