问题
Apologies if the question was asked before. I have some definition of some components as follows (please guide me if it's wrong, because I'm a beginner). What I am trying, is to enumerate all published properties of the derived components, particularly the sub-properties. I am able to enumerate the names of the properties, however, is it possible to enumerate the published properties for which I can access the elements (as in the sub-properties) during the execution of the program? something like returning properties one-by-one like getfirst / getnext until to the end?
type
TStringArray = array of string;
TGenericColumnDef = class(TPersistent)
private
fColumnName : String;
fColumnNumber : Integer;
fColumnDisplay : string;
fColumnDescription : string;
fColumnDataType : integer;
fColumnEditorType : integer;
// fMyEvent: TNotifyEvent;
protected
public
constructor create(AOwner: TComponent); virtual;
published
property ColumnName : String read fColumnName write fColumnName;
property ColumnNumber : integer read fColumnNumber write fColumnNumber;
//property MyEvent: TNotifyEvent read fMyEvent write fMyEvent;
end;
TGenericAsset = class(Tcomponent) //TPersistent
private
{ Private declarations }
fCiteID : TGenericColumnDef;
fCiteType : TGenericColumnDef;
fTitle : TGenericColumnDef;
fAuthor : TGenericColumnDef;
fPropertyCount : integer;
function GetPropertyCount : integer;
function GetNextPropertyIndex: integer;
property CountProperties : integer read GetPropertyCount;// write fPropertyCount
protected
{ Protected declarations }
FOwner: TObject;
public
{ Public declarations }
constructor Create(AOwner: TComponent); override;
destructor destory ; virtual;
function GetColumnNameByColumnNumber(ColumnNumber : Integer) : String;
function GetColumnNames : TStringArray;
// function GetFirst : TGenericColumnDef;
published
property CiteID : TGenericColumnDef read fCiteID write fCiteID;
property CiteType : TGenericColumnDef read fCiteType write fCiteType;
property Title : TGenericColumnDef read fTitle write fTitle;
property Author : TGenericColumnDef read fAuthor write fAuthor;
//property Nthproperty .........
end;
//derived from TGenericAsset
type
TEditedBook = class(TGenericAsset)
private
protected
public
published
property CiteID : TGenericColumnDef read fCiteID write fCiteID;
property Title : TGenericColumnDef read fTitle write fTitle;
property Author : TGenericColumnDef read fAuthor write fAuthor;
end;
Any points or guidelines (sample code) is highly appreciated. Thanks in advance.
回答1:
While it doesn't specifically answer your question, the code below (donated to the old Borland Delphi newsgroups a few years ago by Dr. Peter Below of TeamB) shows how to use RTTI to clone another component. It shows how to get (and set) sub-properties like other objects, enumerated types, and so forth. It should be enough to get you started. I've left Peter's comments in the code, as well as a sample of using it in the form of some sample code below the function. (I've also preserved his code formatting and strange letter casing of some keywords. :)
// Unfortunately there is no easy way to "clone" a component in a way that
// will also preserve event handlers. It can be done using run-time type
// information and routines form the TypInfo unit, though. Try the following
// routine. It is only superficially tested.
Uses TypInfo;
{-- CloneComponent ----------------------------------------------------}
{: Make a copy of a component.
@Param anObj is the component to copy
@Param cloneChildren if true and anObj is a TWincontrol then all its
child controls will also be copied.
@Param aParent is the parent to use if anObj is a TControl.
@Returns the new object reference. It will have the same owner as anObj
and passes into the responsibility of the caller.
@Precondition anObj <> nil
@Desc The method creates a new object of the same class as anObj and then
uses TypInfo routines to copy all published properties. The logic used
for object properties is similar to what the form loading code uses:
if a property refers to a TComponent the component reference is copied.
If it refers to a TPersistent descendent the Assign method is used
to copy the objects contents. Currently TCollections do not receive
any special treatment, which may be necessary. <BR>
Note: the routine will not copy any objects *owned* by anObj, so it
cannot be used as is to clone a top-level container like a form,
frame, or datamodule. Those can be copied using WriteComponent and
ReadComponent with a TMemoryStream.
}{ Created 12.4.2002 by P. Below
-----------------------------------------------------------------------}
Function CloneComponent( anObj: TComponent;
cloneChildren: Boolean = false;
aParent: TWinControl = nil ): TComponent;
Var
numProps, I : Integer;
props: PPropList;
PropInfo: PPropInfo;
obj, obj2: TObject;
Begin { CloneComponent }
Assert( Assigned( anObj ));
Result := TComponentClass( anObj.ClassType ).Create( anObj.Owner );
Try
numProps := GetPropList(anObj, props );
Try
For I := 0 To numProps - 1 Do Begin
PropInfo := props^[I];
Case PropInfo^.PropType^.Kind Of
tkInteger, tkChar, tkEnumeration, tkSet, tkWChar:
SetOrdProp( Result, propinfo,
GetOrdProp( anObj, propinfo ));
tkFloat:
SetFloatProp( Result, propinfo,
GetFloatProp( anObj, propinfo ));
tkString, tkLString:
If not SameText( propinfo^.name, 'Name' ) Then
SetStrProp( Result, propinfo,
GetStrProp( anObj, propinfo ));
tkWString:
SetWideStrProp( Result, propinfo,
GetWideStrProp( anObj, propinfo ));
tkMethod:
SetMethodProp( Result, propinfo,
GetMethodProp( anObj, propinfo ));
tkInt64:
SetInt64Prop( Result, propinfo,
GetInt64Prop( anObj, propinfo ));
tkVariant:
SetVariantProp( Result, propinfo,
GetVariantProp( anObj, propinfo ));
tkInterface:
SetInterfaceProp( Result, propinfo,
GetInterfaceProp( anObj, propinfo ));
tkClass: Begin
obj := GetObjectProp( anObj, propinfo );
If Assigned( obj ) Then Begin
If obj Is TComponent Then
SetObjectProp( Result, propinfo, obj )
Else If obj Is TPersistent Then Begin
obj2 := GetObjectProp( result, propinfo, TPersistent);
If Assigned( obj2 ) Then
TPersistent( obj2 ).Assign( TPersistent(obj));
End; { If }
End; { If }
End; { Case tkClass }
Else
// we don't handle these property types:
// tkArray, tkRecord, tkDynArray
End; { Case }
End; { For }
Finally
FreeMem( props );
End; { Finally }
If anObj Is TControl Then
TControl( result ).Parent := aParent;
If cloneChildren and (anObj Is TWinControl ) Then
For i:= 0 To TWinControl( anObj ).ControlCount-1 Do
CloneComponent( TWinControl( anObj ).Controls[i], true,
TWinControl( Result ) );
Except
Result.Free;
raise
End; { Except }
End; { CloneComponent }
procedure TForm1.GroupBox1MouseDown(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
begin
memo1.lines.add('Click on groupbox '+(sender as TComponent).Name );
end;
procedure TForm1.Button1Click(Sender: TObject);
Var
ctrl: TWinControl;
begin
ctrl := CloneComponent( groupbox1, true, self ) as TWincontrol;
With ctrl Do
SetBounds( left, top+height+8, width, height );
memo1.Lines.add( Format('Controlcount: %d', [ctrl.controlcount]));
end;
来源：https://stackoverflow.com/questions/5442234/enumerating-published-properties-and-subproperties-in-delphi