How can I assign all property values (or if it's not possible only published property values, or some of them) of one class (TComponent) to another instance of the same class? What I want to do is:
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MyComponent1.{property1} := MyComponent2.{property1}; {...} MyComponent2.{propertyN} := MyComponent2.{propertyN}; |
Is there a better and shorter way to do this? I tried this: MyComponent1 := MyComponent2; But it doesn't work. Why not? Can I point to the second component ?
Answer 1:
MyComponent2 and MyComponent1 are pointers to your components, and this kind of assigment leads to MyComponent1 pointing to MyComponent2. But it will not copy its property values.
A better way is to override the assign method of your control, do all property assignment there and call it when you need to copy component attributes. Here's example:
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procedure TMyComponent.Assign(Source: TPersistent); begin if Source is TMyComponent then begin property1 := TMyComponent(Source).property1; { ... } end else inherited Assign(Source); end; |
To assign properties you'll need to set this line in the code:
MyComponent1.Assign(MyComponent2);
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procedure EqualClassProperties(AClass1, AClass2: TObject); var PropList: PPropList; ClassTypeInfo: PTypeInfo; ClassTypeData: PTypeData; i: integer; NumProps: Integer; APersistent : TPersistent; begin if AClass1.ClassInfo <> AClass2.ClassInfo then exit; ClassTypeInfo := AClass1.ClassInfo; ClassTypeData := GetTypeData(ClassTypeInfo); if ClassTypeData.PropCount <> 0then begin GetMem(PropList, SizeOf(PPropInfo) * ClassTypeData.PropCount); try GetPropInfos(AClass1.ClassInfo, PropList); for i := 0to ClassTypeData.PropCount - 1do ifnot (PropList[i]^.PropType^.Kind = tkMethod) then {if Class1,2 is TControl/TWinControl on same form, its names must be unique} if PropList[i]^.Name <> 'Name'then if (PropList[i]^.PropType^.Kind = tkClass) then begin APersistent := TPersistent(GetObjectProp(AClass1, PropList[i]^.Name, TPersistent)); if APersistent <> nilthen APersistent.Assign(TPersistent(GetObjectProp(AClass2, PropList[i]^.Name, TPersistent))) end else SetPropValue(AClass1, PropList[i]^.Name, GetPropValue(AClass2, PropList[i]^.Name)); finally FreeMem(PropList, SizeOf(PPropInfo) * ClassTypeData.PropCount); end; end; end; |
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