GetPropList與TRectangle返回StrokeThickness作爲屬性應該是Stroke類的一部分

Question

我正在使用Delphi Seattle Update1 Win64並嘗試使用RTTI提取屬性。我的目標是將組件屬性序列化爲JSON，因爲我需要在非Delphi環境中使用此信息。

我的問題是關於GetPropList爲TRectangle（例子），以及爲什麼它返回則不能傳遞到GetPropValue，即性質：

1. StrokeThickness類型tkFloat
2. StrokeCap類型tkEnumeration
3. StrokeDash作爲類型tkEnumeration
4. StrokeJoin as type tkEnum關合作。

GetPropList不正確地爲tkClass類型，這是我本來期望，並返回Stroke解析時，Stroke類回報Thickness，Cap，Dash和Join，我可以得到這些正確的價值觀。

問題是執行GetPropValueStrokeThickness會導致異常。因此，我必須特別注意GetPropList返回的「破損」屬性，我想避免這種情況。

起初我還以爲這是與GetPropList返回屬性的問題根本不存在，但我可以執行以下代碼，他們都工作：

Rectangle1.StrokeThickness := 5; //works 

    Rectangle1.Stroke.Thickness := 10; //and also works 

型tkFloat或tkEnumeration工作的其他屬性預計並返回正確的值。

我創建了一個小測試應用程序來嘗試調試這個。我發現在StrokeThickness的情況下，M.Code在函數System.TypeInfo.TPropSet.GetProp（行2397）中爲零，我想解釋爲什麼會導致異常。

附加的是我創建的測試代碼，用於確認我在更大的項目中看到的內容。我將如何處理上面列出的四個屬性而無需特殊情況。

形式：

object Form1: TForm1 
    Left = 0 
    Top = 0 
    Caption = 'Form1' 
    ClientHeight = 202 
    ClientWidth = 542 
    FormFactor.Width = 320 
    FormFactor.Height = 480 
    FormFactor.Devices = [Desktop] 
    DesignerMasterStyle = 0 
    object Rectangle1: TRectangle 
    Position.X = 40.000000000000000000 
    Position.Y = 40.000000000000000000 
    Size.Width = 97.000000000000000000 
    Size.Height = 97.000000000000000000 
    Size.PlatformDefault = False 
    end 
    object StrokeThickness: TButton 
    Position.X = 40.000000000000000000 
    Position.Y = 144.000000000000000000 
    Size.Width = 97.000000000000000000 
    Size.Height = 22.000000000000000000 
    Size.PlatformDefault = False 
    TabOrder = 1 
    Text = 'RTTI' 
    OnClick = StrokeThicknessClick 
    end 
    object Memo1: TMemo 
    Touch.InteractiveGestures = [Pan, LongTap, DoubleTap] 
    DataDetectorTypes = [] 
    Position.X = 152.000000000000000000 
    Position.Y = 40.000000000000000000 
    Size.Width = 353.000000000000000000 
    Size.Height = 129.000000000000000000 
    Size.PlatformDefault = False 
    TabOrder = 2 
    Viewport.Width = 349.000000000000000000 
    Viewport.Height = 125.000000000000000000 
    end 
end 

測試代碼：

unit Unit1; 

interface 

uses 
    System.SysUtils, System.Types, System.UITypes, System.Classes, System.Variants, 
    FMX.Types, FMX.Controls, FMX.Forms, FMX.Graphics, FMX.Dialogs, FMX.StdCtrls, 
    FMX.Controls.Presentation, FMX.Edit, FMX.Objects, FMX.ScrollBox, FMX.Memo; 

type 
    TForm1 = class(TForm) 
    Rectangle1: TRectangle; 
    StrokeThickness: TButton; 
    Memo1: TMemo; 
    procedure StrokeThicknessClick(Sender: TObject); 
    private 
    { Private declarations } 
    public 
    { Public declarations } 
    end; 

var 
    Form1: TForm1; 

implementation 

uses System.TypInfo; 

{$R *.fmx} 

procedure TForm1.StrokeThicknessClick(Sender: TObject); 
var 
    vValue : String; 
    PropList : PPropList; 
    PropInfo : PPropInfo; 
    PropType : PPTypeInfo; 
    PropListCount : Integer; 
    I: Integer; 
begin 
    memo1.Lines.Clear; 

    PropListCount := GetPropList(Rectangle1, PropList); 

    for I := 0 to PropListCount-1 do 
    begin 
    PropInfo := PropList^[I]; 
    PropType := PropInfo^.PropType; 

    Memo1.Lines.Add('Name: '+String(PropInfo^.Name)); 
    Memo1.Lines.Add('PropType: '+String(PropInfo^.PropType^.Name)); 
    Memo1.Lines.Add('PropKind: '+GetEnumName(TypeInfo(TTypeKind), Ord(PropType^.Kind))); 
    Memo1.Lines.Add(''); 
    end; 

    vValue := GetPropValue(Rectangle1, 'Name');    //test string 
    Memo1.Lines.Add('Proprty Name = '+VarToStr(vValue)); 

    vValue := GetPropValue(Rectangle1, 'Height');    //test float 
    Memo1.Lines.Add('Property Height = '+VarToStr(vValue)); 

    vValue := GetPropValue(Rectangle1, 'Sides');    //test enumeration 
    Memo1.Lines.Add('Property Sides = '+VarToStr(vValue)); 

    //The following would cause an exception 
    { 
    vValue := GetPropValue(Rectangle1, 'StrokeThickness'); 
    Memo1.Lines.Add('Property StrokeThickness ='+VarToStr(vValue)); 
    } 

    Rectangle1.StrokeThickness := 5; //works ?? 

    //Still fails after it was explicitly set 
    { 
    vValue := GetPropValue(Rectangle1, 'StrokeThickness'); 
    Memo1.Lines.Add('Property StrokeThickness ='+VarToStr(vValue)); 
    } 

    Rectangle1.Stroke.Thickness := 10; //and also works... as expected 

    //The following with cause an exception 
    { 
    vValue := GetPropValue(Rectangle1, 'StrokeDash'); 
    Memo1.Lines.Add('StrokeDash = '+VarToStr(vValue)); 
    } 

end; 

end. 

Answer 1

使用代碼等

var 
    LProperty: TRttiProperty; 
    LType: TRttiType; 
    LContext: TRttiContext; 
    LArray: TArray<TRttiProperty>; 
begin 
    LContext := TRTTIContext.Create; 
    LType := LContext.GetType(TRectangle); 
    LArray := LType.GetDeclaredProperties; 
    for LProperty in LArray do 
    begin 
    Memo1.Lines.Add('Name: ' + LProperty.Name); 
    Memo1.Lines.Add('PropType: ' + LProperty.PropertyType.Name); 
    Memo1.Lines.Add('PropKind: ' + GetEnumName(TypeInfo(TTypeKind), Ord(LProperty.PropertyType.TypeKind))); 
    if LProperty.IsReadable then 
    begin 
     Memo1.Lines.Add('Value: ' + LProperty.GetValue(Rectangle1).ToString); 
    end 
    else 
    begin 
     Memo1.Lines.Add('Value of the property cannot be read'); 
    end; 
    Memo1.Lines.Add(''); 
    end; 
end;