Help With ADOQuery.Locate

Expert Comment

by:Ephraim Wangoya

ID: 349611112011-02-23

Create a variant array on the fly

Function PositionTable(Var MyDataTable : TADOQuery;{**************************}
                       Const MyKeyFieldStr : String;{List of Fields Seperated by ;}
                       const MyKeyValues : Array of String) : Boolean;
var
  I, Len: Integer;
  SearchValues: Variant;
Begin
  Len := Length(MyKeyValues);
  SearchValues := VarArrayCreate([0, Len-1], varVariant);
  for I := 0 to Len -1 do
    SearchValues[I] := MyKeyValues[I];
  PositionTable := MyDataTable.Locate(MyKeyFieldStr, SearchValues, [loCaseInsensitive]);
End;

LVL 39

Expert Comment

by:Geert G

ID: 349620022011-02-23

there is no need to use var in your function !
actually you must not use it

Function PositionTable(MyDataTable : TADOQuery;
Const MyKeyFieldStr : String;{List of Fields Seperated by ;}
const MyKeyValues : Array of String) : Boolean;

Author Comment

by:malachi223

ID: 349652102011-02-23

Below is my new Code as Suggested and I get an error. Could Not Convert Variant of type(Array Varriant) Into type (String).

Function PositionTable(MyDataTable : TADOQuery;{**************************}
Const MyKeyFieldStr : String;{List of Fields Seperated by ;}
const MyKeyValues : Array of String) : Boolean;
Var SearchValues : Variant;
Idx : Integer;
Len : Integer;
Begin
Len := Length(MyKeyValues);
SearchValues := VarArrayCreate([0, Len-1], varVariant);
for Idx := 0 to Len -1 do
SearchValues[Idx] := MyKeyValues[Idx];
PositionTable := MyDataTable.Locate(MyKeyFieldStr, SearchValues, [loCaseInsensitive]);
End;

LVL 39

Expert Comment

by:Geert G

ID: 349654462011-02-23

new to delphi ?
why not use TDataset ?
you could then use this as a more generic function

what version of delphi do you have ?

function PositionTable(MyDataTable : TDataset;
const MyKeyFieldStr : String;
const MyKeyValues : array of string) : Boolean;
var SearchValues : Variant;
Begin
DynArrayToVariant(SearchValues, @MykeyValues, TypeInfo(string));
Result := MyDataTable.Locate(MyKeyFieldStr, SearchValues, [loCaseInsensitive]);
End;

Expert Comment

by:Ephraim Wangoya

ID: 349663482011-02-23

I just tested the code and it works, unless you are not passing in the correct data to the procedure

Author Comment

by:malachi223

ID: 349697502011-02-24

I am useing Delphi 7 I am not new to dephi though this stupid function sure is making me feel like I am. Something so common and I cant get it :-(
When I use the DynArrayToVariant function it blows up with the following error.
Invalid Variant Type Conversion. Here is the code.

Function PositionTable(MyDataTable : TADOQuery;{**************************}
Const MyKeyFieldStr : String;{List of Fields Seperated by ;}
Const MyKeyValues : Array of String) : Boolean;
Var SearchValues : Variant;
Begin
DynArrayToVariant(SearchValues, @MykeyValues, TypeInfo(String));
PositionTable := MyDataTable.Locate(MyKeyFieldStr, SearchValues, [loCaseInsensitive]);
End;

As far as what I am passing into the routine this is one of the spots the code that calls the routine and blows up. Note the quotes around the SearchChar in the call to PositionTable. There is a field in the table called SearChar.

Procedure CheckRec(ReplacementTable : TADOQuery);
Var SearchChar : String;
begin
SetLength(IndexFieldArray,1);
IndexFieldArray[0] := SearchChar;
If PositionTable(ReplacementTable, 'SearchChar', IndexFieldArray) Then
Begin
End
end;

Expert Comment

by:Ephraim Wangoya

ID: 349699192011-02-24

There is no value assigned to SearchChar, basically your are sending an empty string to be searched. I suppose this is why you are getting errors

Are you trying to pass in a value to this procedure?

procedure CheckRec(ReplacementTable : TADOQuery; const ASearchText: string); overload
begin
   //SetLength(IndexFieldArray,1); //no need for this if you are searching one item
   //IndexFieldArray[0] := SearchChar; 
   If PositionTable(ReplacementTable, 'SearchChar', [ASearchText]) Then
   Begin
   End
end;

//you would call it like
CheckRec(Query1, 'George');

LVL 39

Expert Comment

by:Geert G

ID: 349792522011-02-25

you are not new to delphi ?

why not just use locate directly ?
i don't see any point in writing a secondary wrapper function for that

Procedure CheckRec(ReplacementTable : TADOQuery; SearchText: string);
begin
If ReplacementTable.Locate('SearchColumns', SearchText, [loCaseInsensitive]) then
begin
ShowMessage('By golly, miss molly, you found a record !');
end;
end;

Author Comment

by:malachi223

ID: 349797212011-02-25

Sorry I was missing the line of code that sets the SearchChar it gets set from a table. As for just doing the locate directly it is because the fields and vales of what I am searching for differ depending on the contents of a table. The code I have posted is obviously not my code in its entirety. just the parts that are pertant to the problem. Ewangoya what version of delphi are you useing. Can you also post the exact code you have that works for you becasue so far it is not working for me. Also as a side notenot that it should matter but these routines are in a seperate unit no on the form where the table resides that I am locateing the data. Finally what are you includeing in your uses for this all to work. There must be something different from what I have and what you have if yours works and mine does not.

Accepted Solution

by:Ephraim Wangoya

Ephraim Wangoya earned 1000 total points

ID: 349893222011-02-26

Here is code to do the search as you want
I created an object for that
There is also a small test based on northwind database

unit Unit3;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, DB, ADODB, Grids, DBGrids, StdCtrls;

type
  TForm3 = class(TForm)
    ADOConnection1: TADOConnection;
    ADOQuery1: TADOQuery;
    DBGrid1: TDBGrid;
    DataSource1: TDataSource;
    Button1: TButton;
    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
  private
    { Public declarations }
  end;

var
  Form3: TForm3;

implementation

{$R *.dfm}

uses
  uDBSearch;

procedure ValidateSearch(const AKeyFields: string; ASearchData: Variant);
var
  List: TStringList;
  ErrMsg: string;
begin
  ErrMsg := '';
  if Trim(AKeyFields) = '' then
     ErrMsg := 'No Key Fields specified'
  else if VarIsNull(ASearchData) then
     ErrMsg := 'Search data not specified'
  else
  begin
    if Pos(';', AKeyFields) <= 0 then
    begin
      if VarIsArray(ASearchData) then
        ErrMsg := 'Search data and key fields do not match';
    end
    else
    begin
      if not VarIsArray(ASearchData) then
        ErrMsg := 'Search data and key fields do not match'
      else
      begin
        List := TStringList.Create;
        try
          List.Delimiter := ';';
          List.DelimitedText := AKeyFields;
          if VarArrayHighBound(ASearchData, 1) <> List.Count -1 then
            ErrMsg := 'Search data and key fields do not match'
        finally
          FreeAndNil(List);
        end;
      end;
    end;
  end;

  if ErrMsg <> '' then
    raise Exception.Create(ErrMsg);
end;

procedure TForm3.Button1Click(Sender: TObject);
begin
  if TDBSearch.LocateData(ADOQuery1, 'EmployeeID;LastName;FirstName',
      ['1', 'Davolio', 'Nancy'], [loCaseInsensitive], @ValidateSearch) then
   ShowMessage('Good')
  else
   ShowMessage('Bad');
end;

procedure TForm3.FormCreate(Sender: TObject);
begin
  ADOConnection1.Connected := True;
  ADOQuery1.Open;
end;

end.

unit uDBSearch;

interface

uses
  SysUtils, Classes, Variants, DB;

type
  PSearchValidate = ^TSearchValidate;
  TSearchValidate = procedure(const AKeyFields: string; ASearchData: Variant);

  TDBSearch = class(TObject)
  public
    class function LocateData(ADataset: TDataset; const AKeyFields: string;
      ASearchData: array of string; AOptions: TLocateOptions = [];
      PValidate: Pointer = nil): Boolean; overload;
    class function LocateData(ADataset: TDataset; const AKeyFields: string;
      ASearchData: Variant; AOptions: TLocateOptions = [];
      PValidate: Pointer = nil): Boolean; overload;
  end;

implementation

{ TDBSearch }

class function TDBSearch.LocateData(ADataset: TDataset;
  const AKeyFields: string; ASearchData: array of string;
  AOptions: TLocateOptions; PValidate: Pointer): Boolean;
var
  I, Len: Integer;
  SearchValues: Variant;
begin
  Len := Length(ASearchData);
  if Len = 1 then
    SearchValues := ASearchData[0]
  else
  begin
    SearchValues := VarArrayCreate([0, Len-1], varVariant);
    for I := 0 to Len -1 do
      SearchValues[I] := ASearchData[I];
  end;

  Result := LocateData(ADataset, AKeyFields, SearchValues, AOptions, PValidate);
end;

class function TDBSearch.LocateData(ADataset: TDataset;
  const AKeyFields: string; ASearchData: Variant; AOptions: TLocateOptions;
  PValidate: Pointer): Boolean;
begin
  if Assigned(PValidate) then
     TSearchValidate(PValidate)(AKeyFields, ASearchData);

  Result := ADataset.Locate(AKeyFields, ASearchData, AOptions);
end;

end.