Question

TClientDataSet events

Asked by: moorhouselondon

This must be a really stoopid question, but in TClientDataSet events, such as BeforeInsert, there seems to be no way to assign any of the Index properties within the event code.  The variable that gets passed into the Event is DataSet: TDataSet, but it is not possible to do, say:-

dataset.indexfieldnames:='blah';

Can someone enlighten me as to how to do this within the event coding - I am fed up of having to do this in the coding leading up to the Insertion.  Or maybe there's a better way to do it...

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Asked On
2009-10-30 at 01:10:23ID24857328
Topic

Delphi Programming

Participating Experts
3
Points
500
Comments
8

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Answers

 

by: epasquierPosted on 2009-10-30 at 01:25:23ID: 25700927

indexfieldnames is not a property of TDataSet but of TTable.

So you should write :

if DataSet Is TTable then TTable(DataSet).indexfieldnames:='blah';

 

by: epasquierPosted on 2009-10-30 at 01:26:28ID: 25700931

if you are really sure you will use this event then you can even forget about the if .. then part, and just cast your dataset in TTable

 

by: epasquierPosted on 2009-10-30 at 01:29:19ID: 25700946

sorry I didn't get my cup of coffe my previous post is not complete and therefore has little sense

if you are really sure you will use this event ONLY WITH TTABLEs then you can even forget about the if .. then part, and just cast your dataset in TTable

 

by: senadPosted on 2009-10-30 at 02:08:03ID: 25701150

has not the table component index property?

 

by: epasquierPosted on 2009-10-30 at 02:15:48ID: 25701197

from Delphi Help (translated from french)

IndexFieldNames is an alternate mean to specify the index to use in a table. ... The properties IndexName and IndexFieldNames are mutually exclusive. Affecting one value erases the other.

Main difference is that IndexFieldNames can set more than one index field. If only one index field is needed, moorhouselondon could use TTable(DataSet).IndexName:='blah';

same problem, same solution, and I don't think that using IndexFieldNames with only one field is much less efficient than IndexName

 

by: Geert_GruwezPosted on 2009-10-30 at 02:19:33ID: 25701207

>>beforeinsert
why do you need to set an index field ?

if it would be to retrieve the autoincremented id field, after the insert is done ...

wouldn't that be what you are looking for ?

 

by: moorhouselondonPosted on 2009-10-30 at 02:35:06ID: 25701314

Progress Report

Thanks folks, great to have such prompt help when it's needed first thing in the morning UK time.

I tried epasquier's suggestion and it didn't work because my ClientDataSet is not a TTable.  However, I then tried:-

Tclientdataset(DataSet).indexfieldnames:='id';

which did work, just testing that as I type, I pasted it into the wrong routine inititially which caused a bit of head-scratching, hence the delay in me getting back to you.

Geert_Gruwez: It is the Auto-inc field that I'm after (I'm using mysql), but I seemed to have a lot of bother getting that to work for some reason, so thought I'd do it manually through BeforeInsert/AfterInsert.  That works really well for me, but occasionally I forget to set the Index to Id before doing an Insert, hence my Question here today.

I'm just waiting for my test utility to finish, then I'll report back...

 

by: moorhouselondonPosted on 2009-10-30 at 05:42:05ID: 31647897

Right, well that works fine.

Bulk of points to epasquier for pointing me in the right direction.  Some points too for Geert_Gruwez for mentioning how things should be done - I may revisit this in a future question.

Thanks again for the prompt responses.

20120131-EE-VQP-002

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