RX-Lib Field creation by program.
lazarus / 16-Databases

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iru · 2017-05-19 01:19

Gentlefolk,

Environment: Linux Mint 18.1,laz 1.6,FPC 3.0.0. RX from lazarus-ccr-
svn-5845-components-rx-trunk.zip.

Does anyone have an example of creating fields by program?

I have the following code which crashes on the 'open' with an unknown
field type.

  vField := tField.Create(Self);
  vField.DisplayLabel := 'fredo';
  vField.FieldName := 'laced';
  vField.SetFieldType(ftString);
  RX1.Fields.Add(vField);

  RX1.Open; 

The 'open' code (procedure TField.SetFieldType(AValue: TFieldType) in
Fields.inc is 'empty',no code at all.  

Any help appreciated,Ian.

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ttomas · 2017-05-19 09:54

Never create TField. In your case you need TStringField descendat
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i vField :=
TStringField.Create(Self);...// vField.SetFieldType(ftString);

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iru · 2017-05-19 12:09

hank you ttomas,

That helps  my code and understanding of things, however.....
The 'open' works.

The following code fails with 'No dataset assigned for field: place'
  RX1.Open;
  RX1.First;
  RX1.Edit;
  RX1.FieldByName('place').AsString := '10'; 

There is a complete (I Think) structure:

DBGrid1>DataSource1>RX1.I thought the 'place' field would be relatedto
RX1.

If I add  ' vField.DataSet := RX1'   as follows

  vField.DataSet := RX1;
  RX1.Fields.Add(vField); 

Compiles clean but gives 'Duplicate fieldname: 'place' on
RX1.Fields.Add

I am lost...Any help (examples?) appreciated, Ian.

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mangakissa · 2017-05-20 08:39

How about the oldfasioned way? This is an example for building a
memtable with tbufdataset:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i begin 
ClDataSet := TBufDataset.Create(nil);  with ClDataSet do  begin   
FieldDefs.Add('veldnaam',ftString, 50);   
FieldDefs.Add('waarde',ftString, 255);  end; 
ClDataset.CreateDataset;  ClDataSet.Active := true;end;

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ttomas · 2017-05-20 20:02

Setting DataSet property of Field also adds Field in Fields of
Dataset.
Check SetDataSet method of TField!

vField.DataSet := RX1;
//  RX1.Fields.Add(vField); //Field is added in prev line