Delphi 设计模式：《HeadFirst设计模式》Delphi7代码

1.主题与观察者
{《HeadFirst设计模式》之观察者模式 }
{ 主题与观察者 }
{ 编译工具 ：Delphi7.0 }
{ 联系方式 ：xshlife@163.com }

unit uWeatherReport;

interface

uses
Classes, SysUtils;

type
TObserver = class; { Forward声明，创建两个相互依赖的类 }

{ 抽象主题 }
TSubject = class(TObject)
procedure RegisterObserver(aObserver: TObserver); virtual; abstract;
procedure RemoveObserver (aObserver: TObserver); virtual; abstract;
procedure NotifyObserver; virtual; abstract;
end;

{ 具体主题 }
TWeatherData = class(TSubject)
private
FObservers: TList;
FTemp : Integer;
FHumidity : Integer;
FPresssure: Integer;
public
constructor Create;
destructor Destroy; override;
procedure RegisterObserver(aObserver: TObserver); override;
procedure RemoveObserver (aObserver: TObserver); override;
procedure NotifyObserver; override;
procedure MeasurementsChanged;
procedure SetMeasurements(aTemp, aHumidity, aPresssure: Integer);
end;

{**************************************************************************}

{ 抽象观察者 }
TObserver = class(TObject)
procedure UpDate(Temp, Humidity, Presssure: Integer); virtual; abstract;
procedure Display; virtual; abstract;
end;

{ 具体观察者 }
TCurrentConditionsDisplay = class(TObserver)
private
FTemp : Integer;
FHumidity : Integer;
FWeatherData: TSubject;
public
constructor Create(aWeatherData: TSubject);
destructor Destroy; override;
procedure UpDate(aTemp, aHumidity, aPresssure: Integer); override;
procedure Display; override;
end;

implementation

{ TWeatherData }

constructor TWeatherData.Create;
begin
FObservers := TList.Create;
end;

destructor TWeatherData.Destroy;
begin
FObservers.Clear;
FreeAndNil(FObservers);
inheri