如何正确使接口支持迭代？ [英] How to properly make an interface support iteration?

问题描述

如何从界面公开此TList，如 IEnumerator 或 IEnumerator< IFungibleTroll> ？我正在使用Delphi XE。

这是我有多远：

 单位FungibleTrollUnit; 
 
接口
 
使用
 Windows，消息，SysUtils，
变体，类，图形，
控件，表单，
泛型
 
 type 
 IFungibleTroll = interface 
 ['{03536137-E3F7-4F9B-B1F5-2C8010A4D019}'] 
函数GetTrollName：String; 
函数GetTrollRetailPrice：Double; 
结束
 
 
 TFungibleTrolls = class（TInterfacedObject，IEnumerable< IFungibleTroll>）
 protected 
 FTrolls：TList< IFungibleTroll> ;; 
 
 public 
 // IEnumerable 
函数GetEnumerator：IEnumerator< IFungibleTroll> ;; // 
 //函数GetEnumerator：IEnumerator;超载; 
 
 //查找/搜索应用功能需要搜索。 
 //这个
 
函数FindSingleItemByName（aName：String; patternMatch：Boolean）：IFungibleTroll; 
函数FindMultipleItemsByName（aName：String; patternMatch：Boolean）：IEnumerable< IFungibleTroll> ;; 
函数FindSingleItemByIdentifier（anIdentifer：String）：IFungibleTroll; //使用内部非可见标识符来查找应用程序。 
 
构造函数创建; 
 
属性巨魔：TList< IFungibleTroll>阅读FTrolls // implements IEnumerable< IFungibleTroll> ;;？ 
 private 
 end; 
 
 
 
 
实现
 
 
 {TFungibleTrolls} 
 
构造函数TFungibleTrolls.Create; 
 begin 
 FTrolls：= TList< IFungibleTroll> .Create; 
 
 end; 
 
函数TFungibleTrolls.FindMultipleItemsByName（aName：String; 
 patternMatch：Boolean）：IEnumerable< IFungibleTroll> ;; 
 begin 
 
 end; 
 
函数TFungibleTrolls.FindSingleItemByIdentifier（
 anIdentifer：String）：IFungibleTroll; 
 begin 
 
 end; 
 
函数TFungibleTrolls.FindSingleItemByName（aName：String; 
 patternMatch：Boolean）：IFungibleTroll; 
 begin 
 
 end; 
 
 
 
函数TFungibleTrolls.GetEnumerator：IEnumerator< IFungibleTroll> ;; 
 begin 
 result：= FTrolls.GetEnumerator; 
结束
 
 //函数TFungibleTrolls.GetEnumerator：IEnumerator; 
 // begin 
 // result：= FTrolls.GetEnumerator; // type IEnumerator< IFungibleTroll>或IEnumerator？ 
 // end; 
 
 
结束。 
  

我陷入了三个错误之一，我无法弄清楚如何解决： p>

[DCC错误] FungibleTrollUnit.pas（26）：E2252具有相同参数的方法GetEnumerator已存在
-or -

[DCC错误] FungibleTrollUnit.pas（19）：E2291缺少接口方法的实现IEnumerable.GetEnumerator
-or-
[DCC错误] FungibleTrollUnit.pas（19）：E2291缺少接口方法的实现IEnumerable.GetEnumerator

似乎我必须声明两种形式的GetEnumerator，如果我声明TFungibleTrolls实现IEnumerable，但我似乎无法弄清楚如何做，无论是重载或没有重载，或使用方法解析条款，如下所示：

  function IEnumerable.GetEnumerator = GetPlainEnumerator; //需要方法解析条款？ 
函数GetEnumerator：IEnumerator< IFungibleTroll> ;; 
函数GetPlainEnumerator：IEnumerator; 
  

这可能看起来像是一个非常基本的使用IEnumerable，并使接口支持迭代，我被卡住了。

更新：在没有首先声明 List< T> ，由于 IEnumerable< T> 继承自 IEnumerable 的事实，我陷入了一个裂缝，但是，我的类不是单个获取枚举器方法，而是提供多个类，而且由于我的类不是通用的，所以它不能直接映射到IEnumerable的要求，除非我使用通用的列表< T> 声明。当编译成一个项目（.dproj + .dpr），而不是内置到一个包（.dproj + .dpk）并在IDE中编译时，Marjan的示例可以工作。它可以从命令行，一个包中，而不是在IDE中，在一个包中。

解决方案

不直接回答你的问题（仍然在工作），但这是我做了一个接口枚举器，即接口类支持迭代：

  IList< T> = interface（IInterface）
 [...] 
函数GetEnumerator：TList< T> .TEnumerator; 
 function Add（const Value：T）：Integer; 
结束
 
 type 
 TBjmInterfacedList< T> = class（TBjmInterfacedObject，IList< T）
 strict private 
 FList：TList< T>; 
函数GetEnumerator：TList< T> .TEnumerator; 
 strict protected 
 function Add（const Value：T）：Integer; 
 public 
构造函数创建;覆盖
析构函数覆盖
结束
 
实现
 
构造函数TBjmInterfacedList< T>创建; 
开始
继承; 
 FList：= TList< T>。创建; 
结束
 
析构函数TBjmInterfacedList< T> .Destroy; 
 begin 
 FreeAndNil（FList）; 
继承; 
结束
 
函数TBjmInterfacedList< T> .GetEnumerator：TList< T> .TEnumerator; 
 begin 
结果：= FList.GetEnumerator; 
结束
 
函数TBjmInterfacedList< T> .Add（const Value：T）：整数; 
 begin 
结果：= FList.Add（Value）; 
结束
  

然后，您可以执行以下操作：

  ISite = interface（IInterface）
 ... 
 end; 
 ISites = interface（IList< ISite>）; 
 ... 
 end; 
 
 var 
网站中的网站开始
 ... 
 end; 
  

与实现类，如：

  TSite = class（TBjmInterfacedObject，ISite）
 ... 
 end; 
 TSites = class（TBjmInterfacedList< ISite>，ISites）
 ... 
 end; 
  

更新

示例项目源上传到
http://www.bjmsoftware.com/ delphistuff / stackoverflow / interfacedlist.zip

How can I expose this TList from an interface, as either IEnumerator or IEnumerator<IFungibleTroll>? I am using Delphi XE.

Here's how far I got:

unit FungibleTrollUnit;

interface

uses
  Windows, Messages, SysUtils,
  Variants, Classes, Graphics,
  Controls, Forms,
  Generics.Collections;

type
  IFungibleTroll = interface
    ['{03536137-E3F7-4F9B-B1F5-2C8010A4D019}']
       function GetTrollName:String;
       function GetTrollRetailPrice:Double;
  end;


  TFungibleTrolls = class (TInterfacedObject,IEnumerable<IFungibleTroll>)
      protected
         FTrolls:TList<IFungibleTroll>;

      public
          // IEnumerable
          function GetEnumerator:IEnumerator<IFungibleTroll>;//
//          function GetEnumerator:IEnumerator; overload;

         // find/search app feature requires searching.
         // this

         function FindSingleItemByName(aName:String;patternMatch:Boolean):IFungibleTroll;
         function FindMultipleItemsByName(aName:String;patternMatch:Boolean):IEnumerable<IFungibleTroll>;
         function FindSingleItemByIdentifier(anIdentifer:String):IFungibleTroll;// use internal non-visible identifier to find an app.

         constructor Create;

         property Trolls:TList<IFungibleTroll> read FTrolls; // implements IEnumerable<IFungibleTroll>;??
  private
  end;




implementation


{ TFungibleTrolls }

constructor TFungibleTrolls.Create;
begin
         FTrolls := TList<IFungibleTroll>.Create;

end;

function TFungibleTrolls.FindMultipleItemsByName(aName: String;
  patternMatch: Boolean): IEnumerable<IFungibleTroll>;
begin

end;

function TFungibleTrolls.FindSingleItemByIdentifier(
  anIdentifer: String): IFungibleTroll;
begin

end;

function TFungibleTrolls.FindSingleItemByName(aName: String;
  patternMatch: Boolean): IFungibleTroll;
begin

end;



function TFungibleTrolls.GetEnumerator: IEnumerator<IFungibleTroll>;
begin
  result := FTrolls.GetEnumerator;
end;

//function TFungibleTrolls.GetEnumerator: IEnumerator;
//begin
//  result := FTrolls.GetEnumerator; // type IEnumerator<IFungibleTroll> or IEnumerator?
//end;


end.

I get stuck in one of three errors that I can't figure out how to solve:

[DCC Error] FungibleTrollUnit.pas(26): E2252 Method 'GetEnumerator' with identical parameters already exists -or-

[DCC Error] FungibleTrollUnit.pas(19): E2291 Missing implementation of interface method IEnumerable.GetEnumerator -or- [DCC Error] FungibleTrollUnit.pas(19): E2291 Missing implementation of interface method IEnumerable.GetEnumerator

It seems I must declare two forms of GetEnumerator, if I declare TFungibleTrolls to implement IEnumerable, but I can't seem to figure out how to do it, either with overloads, or without overloads, or using a "method resolution clause", like this:

      function IEnumerable.GetEnumerator = GetPlainEnumerator; // method resolution clause needed?
      function GetEnumerator:IEnumerator<IFungibleTroll>;
      function GetPlainEnumerator:IEnumerator;

This probably seems like a pretty basic use of IEnumerable, and making an Interface support iteration, and yet, I'm stuck.

Update: It seems when I try to do this without first declaring a List<T>, I am falling into a crack caused by the fact that IEnumerable<T> inherits from IEnumerable, and yet, instead of a single get enumerator method, my class must provide multiple ones, and because my class is not a generic, it can't "map itself" to IEnumerable's requirements directly unless I use a generic List<T> declaration. Marjan's sample works, when compiled into a project (.dproj+.dpr) but not when built into a package (.dproj+.dpk) and compiled in the IDE. It works fine from the command line, in a package, but not in the IDE, in a package.

解决方案

Not an answer to your question directly (still working on that), but this is what I did to get an "interfaced enumerator", ie and interfaced class that supports iteration:

IList<T> = interface(IInterface)
  [...]
  function GetEnumerator: TList<T>.TEnumerator;
  function Add(const Value: T): Integer;
end;

type
  TBjmInterfacedList<T> = class(TBjmInterfacedObject, IList<T>)
  strict private
    FList: TList<T>;
    function GetEnumerator: TList<T>.TEnumerator;
  strict protected
    function Add(const Value: T): Integer;
  public
    constructor Create; override;
    destructor Destroy; override;
  end;

implementation

constructor TBjmInterfacedList<T>.Create;
begin
  inherited;
  FList := TList<T>.Create;
end;

destructor TBjmInterfacedList<T>.Destroy;
begin
  FreeAndNil(FList);
  inherited;
end;

function TBjmInterfacedList<T>.GetEnumerator: TList<T>.TEnumerator;
begin
  Result := FList.GetEnumerator;
end;

function TBjmInterfacedList<T>.Add(const Value: T): Integer;
begin
  Result := FList.Add(Value);
end;

And then you can do stuff like:

ISite = interface(IInterface)
  ...
end;
ISites = interface(IList<ISite>);
  ...
end;

var
  for Site in Sites do begin
    ...
  end;

with implementing classes like:

TSite = class(TBjmInterfacedObject, ISite)
  ...
end;
TSites = class(TBjmInterfacedList<ISite>, ISites)
  ...
end;

Update

Example project source uploaded to http://www.bjmsoftware.com/delphistuff/stackoverflow/interfacedlist.zip

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