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 ? ...

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
}

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
>> }
>>

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
}