Problem with copy
lazarus / 16-Databases

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WTDdallas · 2016-06-18 17:17

I have written this code :

procedure AppendRecord(dsSource, dsTarget: tdataset);     // Append
Record  and copy from one Dataset to another
var
    i: Integer;                                                      
       // Requires both Dataset to be open
begin
  dsTarget.append;                                                   
       // Append target

  with dsSource do
  begin
    for i := 0 to FieldCount-1 do                                    
       // For each field
      begin
       try
        dsTarget.fieldbyname(fields.FieldName).value := Fields.Value; 
 // copy Source.Value to Target(source.fieldname).Value
       finally
       end;
      end;
  end;

  dsTarget.post;                                                     
      // Post Target
end; 

I get invalid value,if the a date, crashes on empty date field.
How do i Precheck for valid value?

 How do i Fix that?

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Ñuño_Martínez · 2016-06-18 20:20

Please: use [ code=pascal] [ /code] (the icon with a # over the
smileys) to format your code snippets.  They'll be easier to read.

Also, "WITH" isn't very recommendable and you should use it only if
you really need it (wich means almost never). It may introduce a lot
of hard to track bugs.  And you don't need teh "TRY .. FINALLY .. END"
block, as "FINALLY" is empty.

Since you're not telling to the DataSet what field are you using, it
tries (and success) to assign all fields to the target, as "Value" is
of type "VARIANT".  You should use property "asDateTime" (or
"asString", or "asInteger", or ...) instead of "Value".

So:
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 (* Append
Record  and copy from one Dataset to another *)PROCEDURE AppendRecord
(dsSource, dsTarget:  TDataSet);VAR  i: INTEGER;BEGIN 
dsTarget.Append;  FOR i := 0 TO FieldCount-1 DO   
dsTarget.FieldByName (dsSource.Fields[i].FieldName).asDateTime :=    
dsSource.Fields[i].asDateTime;  dsTarget.PostEND;

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WTDdallas · 2016-06-18 21:59

Quote from: Ñuño_Martínez on June 18, 2016, 10:20:36 pmPlease: use [
code=pascal] [ /code] (the icon with a # over the smileys) to format
your code snippets.  They'll be easier to read.

Also, "WITH" isn't very recommendable and you should use it only if
you really need it (wich means almost never). It may introduce a lot
of hard to track bugs.  And you don't need teh "TRY .. FINALLY .. END"
block, as "FINALLY" is empty.

Since you're not telling to the DataSet what field are you using, it
tries (and success) to assign all fields to the target, as "Value" is
of type "VARIANT".  You should use property "asDateTime" (or
"asString", or "asInteger", or ...) instead of "Value".

So:
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 (* Append
Record  and copy from one Dataset to another *)PROCEDURE AppendRecord
(dsSource, dsTarget:  TDataSet);VAR  i: INTEGER;BEGIN 
dsTarget.Append;  FOR i := 0 TO FieldCount-1 DO   
dsTarget.FieldByName (dsSource.Fields[i].FieldName).asDateTime :=    
dsSource.Fields[i].asDateTime;  dsTarget.PostEND; 
The Hold Idea is to setup a generic Append record, so you don't know
which fields is what, and don't have to.

I was just needed a way to trap the error and skip to next field.

This worked until A non-date value was import into the dataset, which
I fix on import, did prechecking there.

But I want to make a Smarter Append Record, So it can't crash, or at
least skips field.

Sorry didn't know about code# button.
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 [/procedure
AppendRecord(dsSource, dsTarget: tdataset);                         //
Append Record  and copy from one Dataset to anothervar    i: Integer;
                                                             //
Requires both Dataset to be openbegin  dsTarget.append;              
                                            // Append target   with
dsSource do  begin    for i := 0 to FieldCount-1 do                  
                         // For each field      begin       try      
dsTarget.fieldbyname(fields[i].FieldName).value := Fields[i].Value;  
// copy Source.Value to Target(source.fieldname).Value       finally 
    end;      end;  end;   dsTarget.post;                            
                               // Post Targetend; procedure
ReplaceRecord(dsSource, dsTarget: tdataset);                       //
Copy Record from one Dataset to another over existing onevar    i:
Integer;                                                            
 // Requires both Dataset to be openbegin  dsTarget.edit;            
                                                // Append target  
with dsSource do  begin    for i := 0 to FieldCount-1 do             
                              // For each field      begin        try 
      dsTarget.fieldbyname(fields[i].FieldName).value :=
Fields[i].Value;   // copy Source.Value to
Target(source.fieldname).Value         finally        end;      end; 
end;   dsTarget.post;                                                
            // Post Targetend;      ]