Developing a simple MRU List

If you are developing an application and you need a simple MRU list, here I left my system. The MRU acronym stands for Most Recently Used, and that's very useful when we are working with documents and we want to open the last document opened. To implement this in our application in a simple way, we only need to do this:

In our MainMenu item we need to add 5 new subitems called MRU1 to MRU5 and a separator called separatorMRU.

After that, I've designed the following classes to accomplish my goal:

The TMRUGather is the one who manages the information with the MenuItems and the MRU Object. We'll need to create an instance of this class, and it will control the MRU list in the menu section.

The code of the unit is the following:

uMRU.pas:

unit uMRU;

interface

uses
 menus, iniFiles;

type
 TMRU = class(TObject)
     sCaption: array [0 .. 4] of string;
     sPath: array [0 .. 4] of string;
 private
     function GetCaption(Index: Integer): string;
     procedure SetCaption(Index: Integer; Value: string);
     function GetPath(Index: Integer): string;
     procedure SetPath(Index: Integer; Value: string);
 public
     property Caption[Index: Integer]: string read GetCaption write SetCaption;
     property Path[Index: Integer]: string read GetPath write SetPath;
     constructor create();
 end;

 TMRUGather = Class(TObject)
 private
     FMRU: TMRU;
     FMenuItems: array [0 .. 4] of TMenuItem;
     FSeparator: TMenuItem;
     FIniFile: TInifile;
     procedure GetElements();
     procedure SetMRU(const Value: TMRU);
     procedure LoadMRUtoMENU();
 public
     property MRU: TMRU read FMRU write SetMRU;
     constructor create(ini: String; MRU1, MRU2, MRU3, MRU4, MRU5: TMenuItem; separator: TMenuItem);
     destructor Destroy(); override;
     procedure AddToMRU(Path: string; Caption: string);
 End;

implementation

uses
 SysUtils;

{ MRUObject }

constructor TMRU.create;
begin
 self.sCaption[0] := 'MRU1';
 self.sCaption[1] := 'MRU2';
 self.sCaption[2] := 'MRU3';
 self.sCaption[3] := 'MRU4';
 self.sCaption[4] := 'MRU5';

 self.sPath[0] := '';
 self.sPath[1] := '';
 self.sPath[2] := '';
 self.sPath[3] := '';
 self.sPath[4] := '';
end;

function TMRU.GetCaption(Index: Integer): string;
begin
 if (Index >= 0) and (Index <= 4) then
     Result := sCaption[Index]
 else
     Result := '';
end;

function TMRU.GetPath(Index: Integer): string;
begin
 if (Index >= 0) and (Index <= 4) then
     Result := sPath[Index]
 else
     Result := '';
end;

procedure TMRU.SetCaption(Index: Integer; Value: string);
begin
 if (Index >= 0) and (Index <= 4) then
     sCaption[Index] := Value;
end;

procedure TMRU.SetPath(Index: Integer; Value: string);
begin
 if (Index >= 0) and (Index <= 4) then
     sPath[Index] := Value;
end;

{ MRUGather }

procedure TMRUGather.AddToMRU(Path, Caption: string);
var
 MRU1, MRU2, MRU3, MRU4, MRU5: TMenuItem;
 i: Integer;
begin
 MRU1 := FMenuItems[0];
 MRU2 := FMenuItems[1];
 MRU3 := FMenuItems[2];
 MRU4 := FMenuItems[3];
 MRU5 := FMenuItems[4];

 if MRU1.Caption = 'MRU1' then
 begin
     MRU1.Caption := Caption;
     MRU1.Hint := Path;
     MRU.Caption[0] := Caption;
     MRU.Path[0] := Path;
 end
 else if MRU2.Caption = 'MRU2' then
 begin
     MRU2.Caption := Caption;
     MRU2.Hint := Path;
     MRU.Caption[1] := Caption;
     MRU.Path[1] := Path;
 end
 else if MRU3.Caption = 'MRU3' then
 begin
     MRU3.Caption := Caption;
     MRU3.Hint := Path;
     MRU.Caption[2] := Caption;
     MRU.Path[2] := Path;
 end
 else if MRU4.Caption = 'MRU4' then
 begin
     MRU4.Caption := Caption;
     MRU4.Hint := Path;
     MRU.Caption[3] := Caption;
     MRU.Path[3] := Path;
 end
 else if MRU5.Caption = 'MRU5' then
 begin
     MRU5.Caption := Caption;
     MRU5.Hint := Path;
     MRU.Caption[4] := Caption;
     MRU.Path[4] := Path;
 end
 else if (MRU1.Caption <> 'MRU1') and (MRU2.Caption <> 'MRU2') and (MRU3.Caption <> 'MRU3') and (MRU4.Caption <> 'MRU4') and (MRU5.Caption <> 'MRU5') then
 begin
     MRU5.Caption := MRU4.Caption;
     MRU5.Hint := MRU4.Hint;
     MRU4.Caption := MRU3.Caption;
     MRU4.Hint := MRU3.Hint;
     MRU3.Caption := MRU2.Caption;
     MRU3.Hint := MRU2.Hint;
     MRU2.Caption := MRU1.Caption;
     MRU2.Hint := MRU1.Hint;

     MRU1.Caption := Caption;
     MRU1.Hint := Path;
     for i := 0 to 3 do
     begin
         MRU.Caption[4 - i] := MRU.Caption[3 - i];
         MRU.Path[4 - i] := MRU.Path[3 - i];
     end;
     MRU.Caption[0] := Caption;
     MRU.Path[0] := Path;
 end;

 for i := 0 to 4 do
 begin
     FIniFile.WriteString('MENU', 'MRU' + intToStr(i + 1), MRU.Caption[i]);
     FIniFile.WriteString('MENU', 'PATHMRU' + intToStr(i + 1), MRU.Path[i]);
 end;
 LoadMRUtoMENU();
end;

constructor TMRUGather.create(ini: String; MRU1, MRU2, MRU3, MRU4, MRU5: TMenuItem; separator: TMenuItem);
begin
 FMRU := TMRU.create();
 FMenuItems[0] := MRU1;
 FMenuItems[1] := MRU2;
 FMenuItems[2] := MRU3;
 FMenuItems[3] := MRU4;
 FMenuItems[4] := MRU5;
 FSeparator := separator;
 FIniFile := TInifile.create(ini);
 GetElements();
 LoadMRUtoMENU();
end;

destructor TMRUGather.Destroy;
begin
 FreeAndNil(FIniFile);
 FreeAndNil(FMRU);
 inherited;
end;

procedure TMRUGather.GetElements();
var
 i: Integer;
begin
 for i := 0 to 4 do
 begin
     MRU.Caption[i] := FIniFile.ReadString('MENU', 'MRU' + intToStr(i + 1), 'MRU' + intToStr(i + 1));
     MRU.Path[i] := FIniFile.ReadString('MENU', 'PATHMRU' + intToStr(i + 1), '');
     FMenuItems[i].Caption := MRU.Caption[i];
     FMenuItems[i].Hint := MRU.Caption[i];
 end;
end;

procedure TMRUGather.LoadMRUtoMENU();
var
 i: Integer;
 allVisible: boolean;
begin
 allVisible := true;
 for i := 0 to 4 do
 begin
     FMenuItems[i].Visible := (FMenuItems[i].Caption <> 'MRU' + intToStr(i + 1));
     allVisible := allVisible and FMenuItems[i].Visible;
 end;
 FSeparator.Visible := allVisible;
end;

procedure TMRUGather.SetMRU(const Value: TMRU);
begin
 FMRU := Value;
end;

end.

On the Create of the form, we need to declare our MRU object:

 MRUGather: TMRUGather;
 MRUGather := TMRUGather.Create(iniFile, MRU1, MRU2, MRU3, MRU4, MRU5, separatorMRU);

And with the AddToMRU method, we'll add a new item on the entry list. The class manages everything, from adding the MRU inside an Ini file to pushing the list when is full.

     MRUGather.AddToMRU(loadFolder, sCaption);

If the MRU object is running, then we can see the results in our Main Menu Item:

Then, we need to program the events on the MRU subItems to open the document we want.

procedure TfrmMain.MRU1Click(Sender: TObject);
var
 i: Integer;
begin
 for i := 0 to 4 do
     if TMenuItem(Sender).Name = 'MRU' + inttostr(i + 1) then
         if TMenuItem(Sender).Caption <> 'MRU' + inttostr(i + 1) then
             load(MRUGather.MRU.Path[i]);
end;