Delphi中的类/静态常量 [英] Class/Static Constants in Delphi

问题描述

在Delphi中，我想要创建一个与一个类相关联的私有对象，并从该类的所有实例中访问它。在Java中，我会使用：

  public class MyObject {
 private static final MySharedObject mySharedObjectInstance = new MySharedObject ; 
} 
  

或者，如果MySharedObject需要更复杂的初始化，在Java中我可以实例化和初始化它在一个静态的初始化程序块中。

（你可能已经猜到...我知道我的Java，但我对Delphi更新）

无论如何，每次创建MyObject的实例时，我都不想实例化一个新的MySharedObject，但是我希望MySharedObject可以从MyObject的每个实例访问。 （这实际上是记录，这促使我试图弄清楚这一点 - 我使用的是Log4D，我想为每个具有日志功能的类存储一个TLogLogger作为一个类变量。）

在Delphi中做最好的方法是什么？

解决方案

这是我将如何做使用类变量，类过程和初始化块：

  unit MyObject; 
 
接口
 
类型
 
 TMyObject = class 
 private 
 class var FLogger：TLogLogger; 
 public 
类过程SetLogger（value：TLogLogger）; 
类程序FreeLogger; 
结束
 
实现
 
类过程TMyObject.SetLogger（value：TLogLogger）; 
 begin 
 // sanity check here 
 FLogger：= Value; 
结束
 
类程序TMyObject.FreeLogger; 
开始
如果分配（FLogger）然后
 FLogger.Free; 
结束
 
初始化
 TMyObject.SetLogger（TLogLogger.Create）; 
 finalization 
 TMyObject.FreeLogger; 
结束。 
  

In Delphi, I want to be able to create an private object that's associated with a class, and access it from all instances of that class. In Java, I'd use:

public class MyObject {
    private static final MySharedObject mySharedObjectInstance = new MySharedObject();
}

Or, if MySharedObject needed more complicated initialization, in Java I could instantiate and initialize it in a static initializer block.

(You might have guessed... I know my Java but I'm rather new to Delphi...)

Anyway, I don't want to instantiate a new MySharedObject each time I create an instance of MyObject, but I do want a MySharedObject to be accessible from each instance of MyObject. (It's actually logging that has spurred me to try to figure this out - I'm using Log4D and I want to store a TLogLogger as a class variable for each class that has logging functionality.)

What's the neatest way to do something like this in Delphi?

解决方案

Here is how I'll do that using a class variable, a class procedure and an initialization block:

unit MyObject;

interface

type

TMyObject = class
   private
     class var FLogger : TLogLogger;
   public
     class procedure SetLogger(value:TLogLogger);
     class procedure FreeLogger;
   end;

implementation

class procedure TMyObject.SetLogger(value:TLogLogger);
begin
  // sanity checks here
  FLogger := Value;
end;

class procedure TMyObject.FreeLogger;
begin
  if assigned(FLogger) then 
    FLogger.Free;
end;

initialization
  TMyObject.SetLogger(TLogLogger.Create);
finalization
  TMyObject.FreeLogger;
end.

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