persistsettings.pas

jvcl driver development envionment

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                       JEDI-VCL Demo

 Copyright (C) 2002 Project JEDI

 Original author:

 Contributor(s):

 You may retrieve the latest version of this file at the JEDI-JVCL
 home page, located at http://jvcl.sourceforge.net

 The contents of this file are used with permission, subject to
 the Mozilla Public License Version 1.1 (the "License"); you may
 not use this file except in compliance with the License. You may
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 Software distributed under the License is distributed on an
 "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
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// (p3) simple unit that defines save/store interface
unit PersistSettings;

interface
uses
  SysUtils, Classes, IniFiles;

type
  EStorageHandlerError = class(Exception);
  // for convenience, alias TCustomIniFile here so users
  // don't all have to add IniFiles to their uses
  TPersistStorage = class(TCustomIniFile);

  // this interface should be implemente by whoever (form, component) can (and wants to) store
  // their settings (whatever that might be)
  IPersistSettings = interface
  ['{74727C9C-50F6-4C3A-8051-5CC5E64E9EB7}']
    procedure Load(Storage:TPersistStorage);
    procedure Save(Storage:TPersistStorage);
  end;
  
type
  TStorageHandlerFunction = function:TPersistStorage;
  TStorageHandlerMethod = function:TPersistStorage of object;

// call SetStorageHandler to set a function or method that creates and returns a
// TPersistStorage instance. NB! the function/method must be available throughout the
// life-time of the application! This can be accomplished by declaring
// a function in a globally available unit or a method in a class with
// application wide life-time (like the main form)
// You only need to call one of them, not both
procedure SetStorageHandler(AFunction:TStorageHandlerFunction);overload;
procedure SetStorageHandler(AMethod:TStorageHandlerMethod);overload;

// NB! before calling GetStorage, one of the SetStorageHandler procedures
// *must* have been set up with a valid Func parameter that is available
// throughout the life-time of the application (done with SetStorageHandler)!
function GetStorage:TPersistStorage;

// Save a component and any sub-component that implements the IPersistSettings interface
procedure SaveComponents(Root:TComponent;Storage:TPersistStorage);
// Load a component and any sub-component that implements the IPersistSettings interface
procedure LoadComponents(Root:TComponent;Storage:TPersistStorage);

// AutoSave calls GetStorage and then calls SaveComponents
procedure AutoSave(Root:TComponent);

// AutoLoad calls GetStorage and then calls LoadComponents
procedure AutoLoad(Root:TComponent);

implementation

var
  FFunction:TStorageHandlerFunction = nil;
  FMethod:TStorageHandlerMethod = nil;

procedure SetStorageHandler(AFunction:TStorageHandlerFunction);
begin
  FFunction := AFunction;
end;

procedure SetStorageHandler(AMethod:TStorageHandlerMethod);
begin
  FMethod := AMethod;
end;

function GetStorage:TPersistStorage;
begin
  if Assigned(FFunction) then
    Result := FFunction
  else if Assigned(FMethod) then
    Result := FMethod
  else
    raise EStorageHandlerError.Create('No handler assigned for GetStorage!');
end;

procedure SaveComponents(Root:TComponent;Storage:TPersistStorage);
var i:integer;PS:IPersistSettings;
begin
  if Supports(Root,IPersistSettings,PS) then
    PS.Save(Storage);
  for i := 0 to Root.ComponentCount-1 do
    SaveComponents(Root.Components[i],Storage);
end;

procedure LoadComponents(Root:TComponent;Storage:TPersistStorage);
var i:integer;PS:IPersistSettings;
begin
  if Supports(Root,IPersistSettings,PS) then
    PS.Load(Storage);
  for i := 0 to Root.ComponentCount-1 do
    LoadComponents(Root.Components[i],Storage);
end;

procedure AutoSave(Root:TComponent);
var Storage:TPersistStorage;
begin
  Storage := GetStorage;
  try
    SaveComponents(Root,Storage);
    Storage.UpdateFile;
  finally
    Storage.Free;
  end;
end;

procedure AutoLoad(Root:TComponent);
var Storage:TPersistStorage;
begin
  Storage := GetStorage;
  try
    LoadComponents(Root,Storage);
  finally
    Storage.Free;
  end;
end;

end.