Re: Safe cast

[Adam D. Ruppe via Digitalmars-d-learn]

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
}

Re: Safe cast

[drug via Digitalmars-d-learn]

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
}

Re: Safe cast

[Виталий Фадеев via Digitalmars-d-learn]

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
}

Safe cast

[Виталий Фадеев via Digitalmars-d-learn]

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 ? ...