Как изменить значение свойства компонента по имени?

 
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Delphi, Kylix and Pascal
ava
Pakshin A. S. | 04.11.2004, 15:00

function GetProperty(AControl: TPersistent; AProperty: String): PPropInfo;
var
i: Integer;
props: PPropList;
typeData: PTypeData;
begin
Result := nil;
if (AControl = nil) or (AControl.ClassInfo = nil) then
Exit;
typeData := GetTypeData(AControl.ClassInfo);
if (typeData = nil) or (typeData^.PropCount = 0) then
Exit;
GetMem(props, typeData^.PropCount * SizeOf(Pointer));
try
GetPropInfos(AControl.ClassInfo, props);
for i := 0 to typeData^.PropCount - 1 do
begin
with Props^[i]^ do
if (Name = AProperty) then
result := Props^[i];
end;
finally
FreeMem(props);
end;
end;


procedure TForm1.Button1Click(Sender: TObject);
var
propInfo: PPropInfo;
begin
PropInfo := GetProperty(Button1.Font, 'Name');
if PropInfo <> nil then
SetStrProp(Button1.Font, PropInfo, 'Arial');
end;




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You can use RTTI to do this. Here is how to change a particular component:


procedure TForm1.BtnClick(Sender: TObject);
var
p: PPropInfo;
f: TFont;
begin
f := TFont.Create;
{Setup the font properties}
f.Name := 'Arial';
p := GetPropInfo(Sender.ClassInfo, 'Font');
if Assigned(p) then
SetOrdProp(Sender, p, Integer(f));
f.Free;
end;



To get at all the forms loop through the Screen global variable. For each form loop through its Components list calling the above procedure (or something close). If you only create your components at design time that is it. If you create some at runtime and the owner is not the form, then for each component loop through its Components list recursively to get at all the owned components.



Tip by Jeff Overcash



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I am building a routine that checks our forms for validity before deploying them. I would like to use some kind of structure that tests if a component type has access to a certain property, something like: " if (self.Controls[b] has Tag) then ...". Can anyone offer suggestions?
Here's an example of setting a string property for a component if it exists and another for an integer property:


procedure SetStringPropertyIfExists(AComp: TComponent; APropName: String;
AValue: String);
var
PropInfo: PPropInfo;
TK: TTypeKind;
begin
PropInfo := GetPropInfo(AComp.ClassInfo, APropName);
if PropInfo <> nil then
begin
TK := PropInfo^.PropType^.Kind;
if (TK = tkString) or (TK = tkLString) or (TK = tkWString) then
SetStrProp(AComp, PropInfo, AValue);
end;
end;


procedure SetIntegerPropertyIfExists(AComp: TComponent; APropName: String;
AValue: Integer);
var
PropInfo: PPropInfo;
begin
PropInfo := GetPropInfo(AComp.ClassInfo, APropName);
if PropInfo <> nil then
begin
if PropInfo^.PropType^.Kind = tkInteger then
SetOrdProp(AComp, PropInfo, AValue);
end;
end;





Tip by Xavier Pacheco
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