c++ cli - Unable to use dynamic_cast with generics -

-

i have generic class client has single type parameter. type parameter reference type derived base. declare class below:

generic <class t> t : base, gcnew() public ref class client {   t val;   void setval(base ^bval){      val = dynamic_cast<t>(bval);  // error c2682: cannot use 'dynamic_cast' convert 'base ^' 't'    }   };

why compile error when using dynamic_cast convert base 1 of derived classes? expecting cast compile fail @ runtime (by returning nullptr) in case argument of incorrect type.

try dynamic_cast <t^>.

pointers have cast other pointers, handles other handles, , forth.


Comments

Post a Comment

Popular posts from this blog

What can cause "Required Package 'IndyCore' not found" when compiling a Delphi 2010 project? -

-
i have got fresh install of delphi 2010 on windows 8.1. i create new project, , under packages, select "build runtime packages". i compile , error "[dcc fatal error] e2202 required package 'indycore' not found" i have checked: package indycore140.bpl available in $bds\bin directory other indy related packages. indycore.dcp file available in $bds\lib , $bds\lib\debug. this driving me nuts. hints? this command line when enable "show command line" option (line breaks added readability): dcc command line "project2.dpr" c:\delphi\delphi2010\bin\dcc32.exe --no-config -lurtl;vcl;vclx;vclimg;vclactnband;dbrtl;vcldb;vcldbx;bdertl;vcltouch;xmlrtl; dsnap;dsnapcon;teeui;teedb;tee;adortl;vclsmp;vclie;inet;inetdb;webdsnap; websnap;inetdbbde;inetdbxpress;soaprtl;dbxcommondriver;dbxclientdriver; dbxinterbasedriver;dbxmysqldriver;dbexpress;dbxcds;tdbf;intrawebdb_100_140; intraweb_100_140;indycore;indysystem;indyprotocol...
Read more

Change the color of an oval at click in Java AWT -

-
i have draw ovals in java, , @ click change color. beginning tried change color after 20 ms, doesn't work. my code is: public class mycomponentnew extends frame { public graphics2d g2d; public mycomponentnew(string title) { super(title); setsize(400, 550); } @override public void paint(graphics g) { this.g2d = (graphics2d) g; this.g2d.setcolor(color.red); this.g2d.filloval(10, 55, 50, 100); } public void changecolor () { this.g2d.setcolor(color.blue); this.g2d.filloval(10, 55, 50, 100); } } and in class main method have: mycomponentnew m; m = new mycomponentnew("fereastra cu baloane"); m.setvisible(true); m.addwindowlistener(new windowadapter() { @override public void windowclosing(windowevent we) { system.exit(0); } }); try { thread.sleep(20); } catch(interruptedexception e) {} m.changecolor(); the color of oval remains red. ...
Read more