Как присвоить все значения полей одного класса другому такому же классу?
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:
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:
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);
Tip by Serge Gubenko
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 <> 0 then
begin
GetMem(PropList, SizeOf(PPropInfo) * ClassTypeData.PropCount);
try
GetPropInfos(AClass1.ClassInfo, PropList);
for i := 0 to ClassTypeData.PropCount - 1 do
if not (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 <> nil then
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;
Note that this code skips object properties inherited other than TPersistent.
Tip by Gokhan Ersumer