Solved

Sorting Array of records with multiple sort keys

Posted on 2004-03-31
5
707 Views
Last Modified: 2010-04-05
I need a function that will sort an array of records, using multiple keys, i.e. similar to using
ORDER BY customer_no, Inv_date, ord_number in SQL.

The number of records in the array will not be very large, probably only several hundred maximum.

Any guidance will be greatly appreciated.

Alan
0
Comment
Question by:alanjbrown
  • 3
  • 2
5 Comments
 
LVL 27

Expert Comment

by:kretzschmar
Comment Utility
you may use a tlist or tstringlist as your record-container,
rather than an array, then u can use the customsort capability
of this objects.

just ask if you need advice about this.

meikl ;-)
0
 
LVL 1

Author Comment

by:alanjbrown
Comment Utility
Meikl

I think that I need some additional help. In  Delphi help I can't find any reference to  customsort. Is this available in Delphi 4?
An example using  multiple keys would be useful.

Alan
0
 
LVL 27

Accepted Solution

by:
kretzschmar earned 250 total points
Comment Utility
well, a sample

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    Memo1: TMemo;
    procedure Button1Click(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
  private
    fList : TList;
    procedure DisplayList;
  public
    { Public declarations }
  end;

  PToOrderRec = ^TToOrderRec;
  TToOrderRec = record
                  customerName : String[100];
                  Customer_no  : Integer;
                  Inv_Date : TDateTime;
                  OrderNo  : Integer;
                end;


var
  Form1: TForm1;

implementation

{$R *.dfm}

function RandomStr(ALen : Integer) : String;
var i : integer;
begin
  result := '';
  for i := 1 to ALen do
    result := result + chr(random(26)+65);
end;

function RandomInt(Range : Integer) : Integer;
begin
  result := Random(Range);
end;


//sort Customer_no, Inv_Date, OrderNo
function CustomSort(p1,p2 : pointer) : Integer;
var pa, pb : PToOrderRec;  //just to read it better
begin
  pa := PToOrderRec(p1);
  pb := PToOrderRec(p2);
  result := 0;
  if      pa^.Customer_no > pb^.Customer_no then
    result := 1
  else if pa^.Customer_no < pb^.Customer_no then
    result := -1
  else if pa^.Inv_Date > pb^.Inv_Date then
    result := 1
  else if pa^.Inv_Date < pb^.Inv_Date then
    result := -1
  else if pa^.OrderNo > pb^.OrderNo then
    result := 1
  else if pa^.OrderNo < pb^.OrderNo then
    result := -1
  else
    result := 0;
end;

procedure TForm1.DisplayList;
var
  i : integer;
  s : string;
begin
  for i := 0 to flist.Count-1 do
  begin
    s :=     PToOrderRec(fList[i])^.customerName + ' - ';
    s := s + IntToStr(PToOrderRec(fList[i])^.Customer_no) + ' - ';
    s := s + DateToStr(PToOrderRec(fList[i])^.Inv_Date) + ' - ';
    s := s + IntToStr(PToOrderRec(fList[i])^.Orderno);
    memo1.Lines.Add(s);
  end;
  memo1.Lines.Add('<---------------------------------------------->');
end;


procedure TForm1.Button1Click(Sender: TObject);
var
  i : integer;
  p : PToOrderRec;
begin
  //simulate record
  for i := 1 to 100 do
  begin
    new(p);
    p^.customerName := RandomStr(25);
    p^.Customer_no := RandomInt(999999);
    p^.Inv_Date := RandomInt(trunc(now));
    p^.OrderNo := RandomInt(999999);
    fList.Add(p);
  end;
  //Output unsorted
  DisplayList;
  //sort
  flist.Sort(CustomSort);
  //Output sorted
  DisplayList;
  //free memory
  for i := 0 to flist.Count-1 do
    dispose(PToOrderRec(flist[i]));
  flist.Clear;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  flist := TList.Create;
end;


procedure TForm1.FormDestroy(Sender: TObject);
begin
  flist.Free;
end;

end.

just ask if somewhat unclear

meikl ;-)
0
 
LVL 1

Author Comment

by:alanjbrown
Comment Utility
It will not compile. Get error Variants.dcu not found

Alan
0
 
LVL 27

Expert Comment

by:kretzschmar
Comment Utility
hum, sorry,
just remove the variants part from the uses clause
(was introduced with delphi6)

meikl ;-)
0

Featured Post

How your wiki can always stay up-to-date

Quip doubles as a “living” wiki and a project management tool that evolves with your organization. As you finish projects in Quip, the work remains, easily accessible to all team members, new and old.
- Increase transparency
- Onboard new hires faster
- Access from mobile/offline

Join & Write a Comment

This article explains how to create forms/units independent of other forms/units object names in a delphi project. Have you ever created a form for user input in a Delphi project and then had the need to have that same form in a other Delphi proj…
Objective: - This article will help user in how to convert their numeric value become words. How to use 1. You can copy this code in your Unit as function 2. than you can perform your function by type this code The Code   (CODE) The Im…
Excel styles will make formatting consistent and let you apply and change formatting faster. In this tutorial, you'll learn how to use Excel's built-in styles, how to modify styles, and how to create your own. You'll also learn how to use your custo…
This video gives you a great overview about bandwidth monitoring with SNMP and WMI with our network monitoring solution PRTG Network Monitor (https://www.paessler.com/prtg). If you're looking for how to monitor bandwidth using netflow or packet s…

743 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

13 Experts available now in Live!

Get 1:1 Help Now