如果类中的字段是Record，如何确定使用Rtti [英] How to determine using Rtti, if a field from a class is a Record

问题描述

我编写了一个RttiHelper类，该类可以检索一个类的所有字段名称。该过程成功确定了字段是对象还是数组，但无法确定字段是Record。遵循代码：

I coded a RttiHelper class, that among other things, can retrieve all field's names of a class. The procedure succesfully determines if a field is an object or an array, but it cannot determine if a field is a Record. Follows code:

unit Form1
interface
uses RttiHelper;
type
  tMyRec = Record
   ...
  end;      
...
implementation
var MyRec : tMyRec;
procedure FormCreate (Sender: tObject);
begin
  SetRec (@MyRec);
end;

unit RttiHelper
interface
type
  tObjRec =  class
   Rec    : Pointer;
  end; 
  ...
  tRttiHelperClass = class (tObject)
  private  
    fObjRec: tObjRec;
  ...
    procedure GetFieldsNames;
  ...
  public  
  ...
    procedure SetRec (aRec: Pointer);
  ...
  published
  ...
    constructor Create (aOwner: tComponent);
  ...
  end;
implementation
constructor tRttiHelperClass.Create (aOwner: tComponent);
begin
  fCtxt := tRttiContext.Create;
end;
procedure tRttiHelperClass.SetRec (aRec: Pointer);
begin
  private
    fObjectRec.Rec := aRec;
    procedure GetFieldsNames;
end;
procedure tRttiHelperClass.GetFieldsNames;
var f      :  Word    ;
    fields : tRttiType;
begin
  with fRttiContext do begin
        RttiType := GetType (fObjRec.ClassType);
        Fields   := RttiType.GetFields;
         for f := Low (fields) to High (fields) fo begin
             if fields[f].GetValue (tObject (fObjRec^)).IsArray  then // this works
                ...
             if fields[f].GetValue (tObject (fObjRec^)).IsObject then // this works
                ...
             if fields[f].GetValue (tObject (fObjRec^)).IsRecord then // "undeclared identifier IsRecord"
                ...
  end;
end;
end.

我知道要使用Records，必须使用tRttiRecordType，但找不到正确的方法来做到这一点。如何确定某些字段是否为记录的正确代码？
谢谢。

I know that in order to work with Records, I must use tRttiRecordType, but I couldn't find the right way to do this. How is the correct code for determining if some field is a Record? Thanks.

推荐答案

请尝试以下操作：

if fields[f].FieldType.IsRecord then

来自< a href = http://docwiki.embarcadero.com/Libraries/en/System.Rtti.TRttiField.FieldType rel = nofollow noreferrer> System.Rtti.TRttiField.FieldType 和 System.Rtti.TRttiType.IsRecord 。

现在，这里的根本问题是您无法从无类型的指针中解析记录字段。为了做到这一点，请将您的记录作为TValue传递。

Now the underlying problem here is you cannot resolve the record fields from an untyped pointer. In order to do something like that, pass your record as a TValue.

procedure SetRec( aRec: TValue);

这样称呼：

SetRec(TValue.From(MyRec));

有关如何完成此操作并解决记录内容的更完整的教程，请参见将记录转换为序列化表单数据以通过HTTP发送。

For a more complete tutorial how to do this and resolve the contents of a record, see Convert Record to Serialized Form Data for sending via HTTP.

传递TValue有效以及类和其他类型。

Passing TValue works with classes and other types as well.

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