• =?UTF-8?B?0JLQuNGC0LDQu9C40Lkg0KTQsNC0?= =?UTF-8?B?0LXQtdCy?= (28/28) Mar 06 2020 Searching info for object casting with checking class type at
• =?UTF-8?B?0JLQuNGC0LDQu9C40Lkg0KTQsNC0?= =?UTF-8?B?0LXQtdCy?= (21/49) Mar 06 2020 I using now next code:
• drug (4/30) Mar 06 2020 Here x will be null. You can use `enforce(x !is null);` if you want
• Adam D. Ruppe (9/11) Mar 06 2020 or since enforce returns it thing, just do

=?UTF-8?B?0JLQuNGC0LDQu9C40Lkg0KTQsNC0?= =?UTF-8?B?0LXQtdCy?= writes:

Searching info for object casting with checking class type at 
runtime.

Like this:

class A
{
     //
}

class B
{
     int bVar;
}


unittest
{
     A a = new A();

     A x = cast( A )a;     // ok
     A x = cast( B )a;     // ok, but unsafe
     A x = safeCast( B )a; // throw exception
     A x = safeCast( A )a; // ok
}


Searching some like next:

T safeCast( CLS )( CLS o )
{
   ... // checking type of o
   ... // may be check ClassInfo...
   return T;
}

Has function like a safeCast() ?
Or other solution ? ...

=?UTF-8?B?0JLQuNGC0LDQu9C40Lkg0KTQsNC0?= =?UTF-8?B?0LXQtdCy?= writes:

On Friday, 6 March 2020 at 12:35:29 UTC, Виталий Фадеев wrote:
 Searching info for object casting with checking class type at 
 runtime.

 Like this:

 class A
 {
     //
 }

 class B
 {
     int bVar;
 }


 unittest
 {
     A a = new A();

     A x = cast( A )a;     // ok
     A x = cast( B )a;     // ok, but unsafe
     A x = safeCast( B )a; // throw exception
     A x = safeCast( A )a; // ok
 }


 Searching some like next:

 T safeCast( CLS )( CLS o )
 {
   ... // checking type of o
   ... // may be check ClassInfo...
   return T;
 }

 Has function like a safeCast() ?
 Or other solution ? ...


I using now next code:

import std.stdio;

class Base {}

class A : Base {}
class B : Base {}


T safeCast( T, CLS )( CLS o )
{
	if ( typeid( o ) == typeid( T ) )
		return cast(T)o;
	else
		throw new Exception( "casting error" );
}


void main()
{	
     Base a = new A();

     A x1 = cast( A )a;      // ok
     B x2 = cast( B )a;      // ok, but unsafe
     B x3 = safeCast!B( a ); // throw exception
     A x4 = safeCast!A( a ); // ok
}

drug <drug2004 bk.ru> writes:

It's too complex

On 3/6/20 3:45 PM, Виталий Фадеев wrote:
 On Friday, 6 March 2020 at 12:35:29 UTC, Виталий Фадеев wrote:
 Searching info for object casting with checking class type at runtime.

 Like this:

 class A
 {
     //
 }

 class B
 {
     int bVar;
 }


 unittest
 {
     A a = new A();

     A x = cast( A )a;     // ok
     A x = cast( B )a;     // ok, but unsafe


Here x will be null. You can use `enforce(x !is null);` if you want 
exception.

     A x = safeCast( B )a; // throw exception
     A x = safeCast( A )a; // ok
 }

Adam D. Ruppe <destructionator gmail.com> writes:

On Friday, 6 March 2020 at 13:03:22 UTC, drug wrote:
 Here x will be null. You can use `enforce(x !is null);` if you 
 want exception.

or since enforce returns it thing, just do

B b = enforce(cast(B) x);

you can also check easily in if statements:

if(auto b = cast(B) x) {
    // x was a b, use b in here
} else {
   //  x was not b, try something else
}