Solved

RegisterPropertyEditor bug??

Posted on 1998-11-09
9
755 Views
Last Modified: 2012-06-27
Delphi's RegisterPropertyEditor procedure has the following declaration:

procedure RegisterPropertyEditor(PropertyType: PTypeInfo; ComponentClass: TClass; const PropertyName: string; EditorClass: TPropertyEditorClass);

The help file says the following: "Set the PropertyName parameter to restrict the property editor to properties with a specific name as well as the specified property type."

I would like to override the TStrings property editor, but ONLY for properties with a "specific name" (as the help file says) e.g. Address.  Thus for ANY component with a TStrings-derived property called "Address" it must use my property editor, but for all other TStrings-derived properties (e.g. TMemo's "Lines" property) Delphi must use the original property editor.

The problem I'm having is that Delphi uses my editor for all TStrings properties (e.g. TMemo's "Lines" property), instead of only for properties called "Address".

This is what my original code looked like:

RegisterPropertyEditor(TypeInfo(TStrings), nil, 'Address', TAddressPropEd);

The way I got around this problem is to declare my own class that is derived from TStrings:
type
  TAddressStrings = class(TStringList);

RegisterPropertyEditor(TypeInfo(TAddressStrings), nil, 'Address', TAddressPropEd);

The above code works, but I don't understand why it's necessary to derive my own class (if the help file is correct).
(I've tried this in D3 and D4, and both give the same result.)

Thanks,
JB
0
Comment
Question by:JimBob091197
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 5
  • 4
9 Comments
 
LVL 8

Accepted Solution

by:
ZifNab earned 100 total points
ID: 1346301
JimBob,

I'm back for a short time, here's what I know :

Second parameter: is used to restrict a property editor's usage to a particular component type. If this parameter is set to NILL, the property editor is registered for ALL properties of the specified property type.
Third parameter: is valid ONLY if the second parameter is NOT nil. By specifying the name of the property, the property editor can be registered for a single property within a component, even though the component may contain additional properties of the same property type.

e.g. RegisterPropertyEditor(TypeInfo(string), TRkClockStatus, 'Format', TRkClockFormatProperty);

->the TRkClockFormatProperty editor is registered for only the format property of the RlClockStatus component. Other string properties defined in the RkClockStatus component are unaffected by this property editor.

More can be found in this Ray Konopka's book : Developing Custom Delphi3 components.

Regards, Zif.
0
 
LVL 5

Author Comment

by:JimBob091197
ID: 1346302
Thanks Zif.

Your comment "Third parameter: is valid ONLY if the second parameter is NOT nil" is what I was looking for.

The help file only says that you can set 3rd parameter (PropertyName) to "the property editor to properties with a specific name as well as the specified property type."

Note that "property type" is the 1st parameter, and the help file says nothing about what happens to the 3rd parameter (PropertyName) if the 2nd parameter (ComponentClass) is nil.

I figured this must be the case, else a bug, but thanks for clearing it up for me.

Cheers,
Dave
0
 
LVL 5

Author Comment

by:JimBob091197
ID: 1346303
Sorry, 2nd paragraph above should read:

The help file only says that you can set 3rd parameter (PropertyName) to "RESTRICT the property editor to properties with a specific name as well as the specified property type."

-Dave

0
Industry Leaders: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

 
LVL 8

Expert Comment

by:ZifNab
ID: 1346304
Glad I could be of assitance. JB, seeing your q'ns : you must almost have finished a great new component package?
0
 
LVL 5

Author Comment

by:JimBob091197
ID: 1346305
Not component package, but app!  ;-)  I will keep you informed...  I want to have a web site finished for it by end of November.

-Dave

0
 
LVL 8

Expert Comment

by:ZifNab
ID: 1346306
Hey Great! Let me know of it, surely!
0
 
LVL 5

Author Comment

by:JimBob091197
ID: 1346307
Will do!

(For a sneak-preview go to http://www.geocities.com/SiliconValley/Lakes/9940/)

-Dave

0
 
LVL 8

Expert Comment

by:ZifNab
ID: 1346308
JB, woow. Nice! Now I understand why you were so silently!
0
 
LVL 5

Author Comment

by:JimBob091197
ID: 1346309
Glad you liked it.  I'll be sure to keep you up-to-date.
0

Featured Post

Free Tool: SSL Checker

Scans your site and returns information about your SSL implementation and certificate. Helpful for debugging and validating your SSL configuration.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

This article explains how to create forms/units independent of other forms/units object names in a delphi project. Have you ever created a form for user input in a Delphi project and then had the need to have that same form in a other Delphi proj…
Introduction Raise your hands if you were as upset with FireMonkey as I was when I discovered that there was no TListview.  I use TListView in almost all of my applications I've written, and I was not going to compromise by resorting to TStringGrid…
Exchange organizations may use the Journaling Agent of the Transport Service to archive messages going through Exchange. However, if the Transport Service is integrated with some email content management application (such as an antispam), the admini…

733 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question