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Lutz Kutscher
Guest
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 Posted: Wed Dec 03, 2003 1:38 pm Post subject: Adding calculated fields at run time |
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Hi,
I've got a form, that enables the user to select fields for a query:
PartNo, SalesCount, Date ...
If the user selects "PartNo" to be displayed in the result, I want to add a
field "PartName".
The data shown in PartName is loaded from a table that's not part of the
query,
so I wanted to add it as calculated field.
How can I add a calculated field at runtime?
--
_____________________________________
Lutz Kutscher
Pattburg Poetzsch GmbH & Co KG
Tel. +49 461 773 15 60
Fax +49 461 773 15 15
[email]LKutscher (AT) graensen (DOT) dk[/email]
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Ross B.
Guest
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| Posted: Wed Dec 03, 2003 3:08 pm Post subject: Re: Adding calculated fields at run time |
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"Lutz Kutscher" <LKutscher (AT) Graensen (DOT) dk> wrote
| Quote: | Hi,
I've got a form, that enables the user to select fields for a query:
PartNo, SalesCount, Date ...
If the user selects "PartNo" to be displayed in the result, I want to add
a
field "PartName".
The data shown in PartName is loaded from a table that's not part of the
query,
so I wanted to add it as calculated field.
How can I add a calculated field at runtime?
--
_____________________________________
Lutz Kutscher
Pattburg Poetzsch GmbH & Co KG
Tel. +49 461 773 15 60
Fax +49 461 773 15 15
[email]LKutscher (AT) graensen (DOT) dk[/email]
|
You can add calced fields at runtime. By creating and instance of the Field.
procedure AddCalcedField(aDataSet,aFieldName,aDataType);
F:TField;
begin
F:=TField.Create(aDataSet);
// F.FieldKind:=fkInternalCalc; <--- Look at the diff btw fkInternal and
ftCalcl
F.FieldKind:=fkCalc;
F.FieldName:=aFieldName;
case aDataType of
ftInteger:F.DataType:=ftInteger;
...
ftString:F.DataType:=ftString;
end;
.....
Note if you are opening and closing a query and possibly
selecting/deselecting multiple dynamically calced fields then be sure to
remove the fields you may no longer need while adding the ones you do need.
Ross B.
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Wayne Niddery [TeamB]
Guest
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| Posted: Wed Dec 03, 2003 5:44 pm Post subject: Re: Adding calculated fields at run time |
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Lutz Kutscher wrote:
| Quote: |
I've got a form, that enables the user to select fields for a query:
PartNo, SalesCount, Date ...
If the user selects "PartNo" to be displayed in the result, I want to
add a field "PartName".
The data shown in PartName is loaded from a table that's not part of
the query,
so I wanted to add it as calculated field.
How can I add a calculated field at runtime?
|
If you are generating the query dynamically anyway, why not add it (a join)
to the query itself?
--
Wayne Niddery - Logic Fundamentals, Inc. (www.logicfundamentals.com)
RADBooks: http://www.logicfundamentals.com/RADBooks.html
"It is error alone which needs the support of government. Truth can
stand by itself." - Thomas Jefferson
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Lutz Kutscher
Guest
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| Posted: Thu Dec 04, 2003 2:08 pm Post subject: Re: Adding calculated fields at run time |
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"Wayne Niddery [TeamB]" <wniddery (AT) chaffaci (DOT) on.ca> schrieb im Newsbeitrag
news:3fce212e$1 (AT) newsgroups (DOT) borland.com...
| Quote: | If you are generating the query dynamically anyway, why not add it (a
join)
to the query itself?
.... because the data in that field originates from a database on a different |
server.
Anyway, I found a solution.
I added the following code to the BeforeOpen-Handler of the query:
Query.FieldDefs.Update;
if Query.FieldDefs.IndexOf('PartNo') > -1 then
begin
TDataSetCracker(Query).CreateFields;
with TStringField.Create(Query) do begin
Name := PartNameComponent; //defined as constant
FieldName := PartNameField;//defined as constant
DataSet := Query;
FieldKind := fkCalculated;
end;
end;
In the AfterClose-Handler I added:
Query.Fields.Clear;
.... now it works.
| Quote: | Lutz Kutscher wrote:
I've got a form, that enables the user to select fields for a query:
PartNo, SalesCount, Date ...
If the user selects "PartNo" to be displayed in the result, I want to
add a field "PartName".
The data shown in PartName is loaded from a table that's not part of
the query,
so I wanted to add it as calculated field.
How can I add a calculated field at runtime?
|
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