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Report From: Delphi-BCB/VCL/Type Info [ Add a report in this area ]

Report #: 29907

Status: Closed

SetPropValue on an enumeration fails with varOleStr variant

Project: Delphi

Build #: 9.0.1882.30496

Version: 9.0

Submitted By: Piotr Szturmaj

Report Type: Crash / Data loss / Total failure

Date Reported: 6/7/2006 2:52:27 PM

Severity: Commonly encountered problem

Last Updated: 3/20/2012 2:24:39 AM

Platform: All platforms

Internal Tracking #: 240469

Resolution: Fixed (Resolution Comments)

Resolved in Build: : 11.0.2565.3426

Duplicate of: None

Voting and Rating

Overall Rating: (3 Total Ratings)

5.00 out of 5

Total Votes: None

Description

Calling SetPropValue with WideString as Value fails on enumerated properties; See Steps

Steps to Reproduce:

Open, build and run the attached project
Press Button labeled "String"
No error
Press Button labeled "WideString"
Error occurs
The only differenece between a and b is that one is a string and the other is a widestring

<sysop>
Original Steps:
</sysop>
1. Add TMemo and TButton to form
2. Add TypInfo to uses clause
3. Call SetPropValue(Memo1, 'Align', WideString('alClient')); in Button1Click

exp: should set align to alClient
act:

---------------------------
Debugger Exception Notification
---------------------------
Project Project2.exe raised exception class EVariantTypeCastError with message 'Could not convert variant of type (OleStr) into type (Double)'.
---------------------------
Break Continue Help
---------------------------

Workarounds

1. Open TypInfo.pas and find procedure:

procedure SetPropValue(Instance: TObject; PropInfo: PPropInfo; const Value: Variant);

around line 675 there is:

tkEnumeration:
  if VarType(Value) = varString then

should be:

tkEnumeration:
  if VarIsStr(Value) then
  // checks for varString and varOleStr(widestrings)

Alternatively use this helper method:

procedure SetPropValue(Instance: TObject; const PropName: string;
  const Value: Variant);
begin
  if PropIsType(Instance, PropName, tkEnumeration) and
    (VarType(Value) = varOleStr) then
    TypInfo.SetPropValue(Instance, PropName, AnsiString(Value))
  else
    TypInfo.SetPropValue(Instance, PropName, Value);
end;

Attachment

qc29907.zip

Comments

Sebastian Modersohn at 6/7/2006 3:03:06 PM -

I can reproduce this with BDS2006 Upd 2. I've slightly modified your steps to mention the actual error message etc.

Piotr Szturmaj at 6/7/2006 3:11:35 PM -

Thanks, I'm using this helper procedure to avoid this bug:

procedure SetPropValue(Instance: TObject; const PropName: string;
  const Value: Variant);
begin
  if PropIsType(Instance, PropName, tkEnumeration) and
    (VarType(Value) = varOleStr) then
    TypInfo.SetPropValue(Instance, PropName, AnsiString(Value))
  else
    TypInfo.SetPropValue(Instance, PropName, Value);
end;

Sebastian Modersohn at 6/8/2006 3:51:31 AM -

I've added your helper method to the workaround.

David Dean at 7/17/2006 12:10:02 PM -

I have uploaded a new project to demonstrate this report.
It should better explain why this isn't a Test Case error

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