如何使用delphi 2010 rtti设置数组长度 [英] how to set array length with delphi 2010 rtti
本文介绍了如何使用delphi 2010 rtti设置数组长度的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
如何在运行时设置数组长度?
setLength(t.GetProperty(‘Propertys’),3);
how to set array length in runtime ? setLength(t.GetProperty('Propertys'),3); ????
unit Unit3;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;
type
TSubProperty = Class
private
Fitem2: Integer;
Fitem1: String;
procedure Setitem1(const Value: String);
procedure Setitem2(const Value: Integer);
published
property item1:String read Fitem1 write Setitem1;
property item2:Integer read Fitem2 write Setitem2;
End;
TArraySubPropertys=array of TSubProperty;
TmyObject = Class
private
FPropertys: TArraySubPropertys;
procedure SetPropertys(const Value: TArraySubPropertys);
published
property Propertys:TArraySubPropertys read FPropertys write SetPropertys;
End;
TForm3 = class(TForm)
Button1: TButton;
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;
var
Form3: TForm3;
implementation
{$R *.dfm}
procedure TForm3.Button1Click(Sender: TObject);
var
myObject:TmyObject;
ctx : TRttiContext;
t : TRttiType;
obj:TObject;
begin
myObject :=TmyObject.Create;
ctx := TRttiContext.Create;
t := ctx.GetType(myObject.ClassType);
// setLength(t.GetProperty('Propertys'),3); ????????????????????????????????????
obj:= (t.GetProperty('Propertys').PropertyType as TRttiDynamicArrayType).ElementType.AsInstance.MetaclassType.Create;
//showmessage(obj.toStirng); --> TSubProperty
t.GetProperty('Propertys').getValue(myObject).setArrayElement(0,obj);
obj:= (t.GetProperty('Propertys').PropertyType as TRttiDynamicArrayType).ElementType.AsInstance.MetaclassType.Create;
t.GetProperty('Propertys').getValue(myObject).setArrayElement(1,obj);
obj:= (t.GetProperty('Propertys').PropertyType as TRttiDynamicArrayType).ElementType.AsInstance.MetaclassType.Create;
t.GetProperty('Propertys').getValue(myObject).setArrayElement(2,obj);
{
myObject.Propertys[0] :=TSubProperty.Create;
myObject.Propertys[0].item1 :='x';
myObject.Propertys[0].item2 :=1;
myObject.Propertys[1] :=TSubProperty.Create;
myObject.Propertys[1].item1 :='y';
myObject.Propertys[1].item2 :=2;
myObject.Propertys[2] :=TSubProperty.Create;
myObject.Propertys[2].item1 :='z';
myObject.Propertys[2].item2 :=3;
ShowMessage(myObject.Propertys[2].item1);
FreeAndNil(myObject.Propertys[2]);
FreeAndNil(myObject.Propertys[1]);
FreeAndNil(myObject.Propertys[0]);
}
FreeAndNil(myObject);
end;
{ TSubProperty }
procedure TSubProperty.Setitem1(const Value: String);
begin
Fitem1 := Value;
end;
procedure TSubProperty.Setitem2(const Value: Integer);
begin
Fitem2 := Value;
end;
{ TmyObject }
procedure TmyObject.SetPropertys(const Value: TArraySubPropertys);
begin
FPropertys := Value;
end;
end.
编辑:
此代码更改了数组的长度,但是错误。
是一个随机值,而不是5。(19736192)
This code changes the length of the array , but wrong. Is a random value instead of 5. (19736192)
procedure TForm3.Button3Click(Sender: TObject);
var
myObject:TmyObject;
ctx : TRttiContext;
t : TRttiType;
v:TValue;
len:Longint;
p:pointer;
begin
myObject :=TmyObject.Create;
ctx := TRttiContext.Create;
t := ctx.GetType(myObject.ClassType);
V := t.GetField('FPropertys').GetValue(myObject);
len:=5;
p:=v.GetReferenceToRawData;
ShowMessage(inttostr(integer(@myObject.FPropertys))); //19795652
ShowMessage(inttostr(integer(p))); //19795672
DynArraySetLength(p,v.TypeInfo,1,@len);
t.GetField('FPropertys').SetValue(myObject,v);
ShowMessage(inttostr(length(myObject.Propertys))); //array length=19736192 ???
end;
编辑2:
@Robert Love ,感谢您的答复,但问题仍然存在。
(Embarcadero®Delphi®2010版本14.0.3513.24210)
@Robert Love, thank you for reply but problem continues. (Embarcadero® Delphi® 2010 Version 14.0.3513.24210 )
单击button2
无效的指针操作。
click button2 invalid pointer operation.
procedure TForm7.Button2Click(Sender: TObject);
var
myObject:TmyObject;
ctx : TRttiContext;
t : TRttiType;
v : Tvalue;
p : Pointer;
Len : Longint;
begin
myObject :=TmyObject.Create;
ctx := TRttiContext.Create;
t := ctx.GetType(myobject.ClassType);
V := t.GetProperty('Propertys');
Len := 3;
P := V.GetReferenceToRawData;
DynArraySetLength(P,V.TypeInfo,1,@Len); // error invalid pointer operation
ShowMessage(inttostr(length(myObject.Propertys)));
end;
推荐答案
您可以使用DynArraySetLength函数。
You can use the DynArraySetLength Function.
var
...
V : TValue;
Len : LongInt;
P : Pointer;
begin
...
V := t.GetProperty('Propertys');
Len := 3;
P := V.GetReferenceToRawData;
DynArraySetLength(P,V.TypeInfo,1,@Len);
...
end;
我在 RttiUtils.pas 。
这篇关于如何使用delphi 2010 rtti设置数组长度的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!
查看全文