继承泛型和嵌套记录助手

Question

我正在尝试在 Delphi 10.1 Berlin 中执行以下操作，但是编译器 return 消息 "F2084 Internal Error: AV0A785E48-R000000-10-0":

TMyType = (mtValue1, mtValue2);

TMyBaseClass = class
private
  FMyType: TMyType;
public
  property MyType: TMyType read FMyType write FMyType;
end;

TMyClass = class(TMyBaseClass)
private
  FOtherField: Integer;
public
  property OtherField: Integer read FOtherField write FOtherField;
end;

TMyBaseProcess1<T: TMyBaseClass> = class
strict private
  FMyClass: T;
strict protected
  type
    TMyTypeHelper = record Helper for TMyType
    public
      function ToString: string;
    end;
public
  constructor Create(AMyClass: T);
  procedure DoSomething;
end;

TMyProcess1 = class(TMyBaseProcess1<TMyClass>)
end;

TMyBaseProcess2<T: TMyBaseClass> = class
strict private
  FMyClass: T;
strict protected
  type
    TMyTypeHelper = record Helper for TMyType
    public
      function ToInteger: Integer;
    end;
public
  constructor Create(AMyClass: T);
  procedure DoSomethingElse;
end;

TMyProcess2 = class(TMyBaseProcess2<TMyClass>)
end;

TMyBaseProcess1 中的helper 与TMyBaseProcess2 中的helper 完全不同。我可以毫无问题地将助手和 class 分开。我只想知道为什么我不能把他们留在一起。

有人知道问题出在哪里吗？我可以这样使用泛型、嵌套记录助手和继承吗？

Answer 1

你不能有两个助手指向相同的 class 类型在你的情况下 TMyType

来自文档..

You can define and associate multiple helpers with a single type. However, only zero or one helper applies in any specific location in source code.

在 classes

之外使用 helper

TMyTypeHelper = record Helper for TMyType
    public
      function ToInteger: Integer;
      function ToString: string; 
    end;

继承泛型和嵌套记录助手

Inheritance with generics and nested record helper

delphi

generics

inheritance

record

helper