SetPropValue by Name

[egnew 3]

I can set the property of a component on a form by value:

SetPropValue(TopPanel,'align',alBottom);

 

I want to be able to set the property using the name of the value as a string:

SetPropValue(TopPanel,'align','alBottom');

 

How can this be accomplished?

 

Thanks

[programmerdelphi2k 237]

in fact, in RAD 11.3 "  SetPropValue(Button1, 'Align', 'alRight'); " works... because the "variant" is accepted and internally is used as "tkEnumeration:" type.

look at "procedure SetPropValue(Instance: TObject; PropInfo: PPropInfo; const Value: Variant);" in System.TypInfo.pas

---> SetEnumProp(Instance, PropInfo, VarToStr(Value))

--------> procedure SetEnumProp(Instance: TObject; PropInfo: PPropInfo;  const Value: string);  get the "name" of each value in TAlign and compare it.... if ok, result "Data := GetEnumValue(PropInfo^.PropType^, Value);"

 

------- edited ------

see "System.TypInfo.Set/GetVariantProp" + SetPropValue() usage!

https://docwiki.embarcadero.com/Libraries/Sydney/en/System.TypInfo.SetVariantProp

https://docwiki.embarcadero.com/Libraries/Sydney/en/System.TypInfo.GetVariantProp

 

or 

look this

https://stackoverflow.com/questions/45987321/change-component-properties-using-setpropvalue-and-rtti-with-delphi-tokyo

Edited March 22, 2023 by programmerdelphi2k

[egnew 3]

I checked the links you provided and do not yet see a solution.   I can just use SetPropValue when the property is a simple type of sting, integer, float, etc.  But here the property is a type.

 

I am using Align as an example type, as it is a property of all TControl components:

property Align: TAlign read FAlign write SetAlign default alNone;

I dynamically create components at runtime using text commands and set the values of the components from the text.  The command to create a panel aligned to TOP is "PANEL /ALIGN=TOP" which will be changed to "PANEL /ALIGN=alTOP" in the new version.  Once I have this working, I can set any property in a component without knowledge of the component.  In the current implementation, I have to deal with each property with a type using functions similar to this:

 

function SetAlign(p_Control: TControl; p_Value: String);

begin

    if SameText(p_Setting,'TOP') then

      p_Control.Align := alTop

    else if SameText(p_Setting,'BOTTOM') then

     p_Control.Align := alBottom

     etc...

end;

 

I validate a property name using this:
function GetPropertyType(p_Component: TComponent; const p_PropertyName: String): String;
var
  v_Context: TRttiContext;
  v_Property: TRttiProperty;
begin
  v_Property := v_Context.GetType(p_Component.ClassType).GetProperty(p_PropertyName);
  Result := v_Property.PropertyType.ToString;
end;

 

I am attempting to resolve these problems:

 

1)  How do I get the current value of the property?

 

2)  How do I change the value of a property when the property is a type?  That is the question posted here.

 

3)  How do I validate the string that identifies the new property value?

I can obtain valid strings for TAlign using the following:

for I := Ord(Low(TAlign)) to Ord(High(TAlign)) do
  p_Memo.Lines.Add(GetEnumName(TypeInfo(TAlign),I))

 

However, I have not been able to determine how to do this for a type I don't know ahead of time using a parameter like:

for I := Ord(Low(p_Type)) to Ord(High(p_Type)) do
  p_Memo.Lines.Add(GetEnumName(TypeInfo(p_Type),I))

 

Thanks

 

 

 

[programmerdelphi2k 237]

1)     var LVal : variant := GetPropValue(Panel1, 'Align'); // get it value

 

2)  will be this?  {case}    if VarType( LVal ) = varUString { varString, etc... } then   SetPropValue(Button1, 'Align',   string( LVal )  );
 

 

Edited March 22, 2023 by programmerdelphi2k

[egnew 3]

Thanks very much.

 

1 - Works Perfectly

2 - Works Perfectly

3 -  Any idea how to the names of the type values?  I can do it as shown in my previous email by specifying the type.  I need to do it from the type name instead.

 

4 - I used this code to get the property type.  Is there a better way?

 

function GetPropertyType(p_Component: TComponent; const p_PropertyName: String): String;
var
  v_Context: TRttiContext;
  v_Property: TRttiProperty;
begin
  v_Property := v_Context.GetType(p_Component.ClassType).GetProperty(p_PropertyName);
  Result := v_Property.PropertyType.ToString;
end;

 

Thanks

[egnew 3]

3)  Not a problem.  I realized I didn't need the list of values.  I can try the provided value.  An "invalid property element: <value>" exception is returned.

 

However, if you have a solution, that would be useful.

 

Thanks again.

[programmerdelphi2k 237]

for sure, email me

[KodeZwerg 54]

Maybe this helps you as it helped me.

That method looks if property is available and set it.

uses
  TypInfo, Rtti;

function SetProperty(const AControl: TControl; const AProperty: string; const AValue: TValue): Boolean;
var
  LControl: TControl;
  LRttiContext: TRttiContext;
  LRttiProperty: TRttiProperty;
begin
  Result := False;
  try
    LControl := AControl;
    LRttiProperty := LRttiContext.GetType(LControl.ClassType).GetProperty(AProperty);
    if ((LRttiProperty <> nil) and (LRttiProperty.Visibility in [mvPrivate, mvProtected, mvPublic, mvPublished])) then
    begin
      LRttiProperty.SetValue(LControl, AValue);
      Result := True;
    end;
  except
  end;
end;

and it can be used like:

SetProperty(AControl, 'Caption', AValue);

 

[egnew 3]

KodeZwerg.

I had a solution using just System.TypInfo, which works for all simple types.

try
    SetPropValue(p_Component,p_PropertyName,p_PropertyValue);
except
...

But your version is better as it allows me to set all properties.

Example:  SetPropertyValue(TControl(MyFDConnection.Params),'UserName','MyUserName');

 

Thank you very much.