www.digitalmars.com         C & C++   DMDScript  

digitalmars.D - Strange enum

reply orgoton <orgoton mindless.com> writes:
I have this in a class:

enum ActorType:ubyte
{Unit=0, Building=1, Other=2
}

then,
class Actor
{
this()
{
assert(this.getType()<5); //THIS FAILS
}
(...)
public final ActorType type=ActorType.Other;
protected ubyte getType()
{
return cast(ubyte)type;
}

}

In a static constructor, an Actor is created to test another class, and the
program ends in an assert error.
Apr 11 2007
parent =?ISO-8859-1?Q?R=e9my_Mou=ebza?= <ray.jay.ay.moueza gmail.com> writes:
orgoton Wrote:


 I have this in a class:
 
 enum ActorType:ubyte
 {Unit=0, Building=1, Other=2
 }
 
 then,
 class Actor
 {
 this()
 {
 assert(this.getType()<5); //THIS FAILS
 }
 (...)
 public final ActorType type=ActorType.Other;
 protected ubyte getType()
 {
 return cast(ubyte)type;
 }
 
 }
 
 In a static constructor, an Actor is created to test another class, and the
program ends in an assert error.



In Java, one declare constants with final. In D we use the const keyword. Note
that this has nothing to do with C++ const type qualifier. There is a certainly
a bunch of code in your program that assign a new value to your Actor.type
variable. Using const, you'll get a compile time error. 
final is use to explicitly ask the D compiler to make a non polymorphic method
(C++ virtual function): by default the D compiler calculate what should be
polymorphic or not and optimises in consequences. 

I hope this information helps, 


import std.stdio ;

class ConsoleOutput
{
    this () {}

    ConsoleOutput opShl (T) ( T something )
    {   
        writef ( something );
        return this ;
    }
}

ConsoleOutput cout ;

static this ()
{
    cout = new ConsoleOutput ;
}

enum ActorType : ubyte
{
    Unit = 0, 
    Building = 1, 
    Other = 2
}

class Actor
{
    this ()
    {
        cout << "constructor " << \n ;
        cout << this.getType () << \n ;

        this.type = cast ( ActorType ) 10 ; // without const Ok, with const:
compile time error. 
        assert ( this.getType () < 5, "problem" ); //THIS FAILS
    }
    //public final ActorType type = ActorType.Other ;
    public const ActorType type = ActorType.Other ;
    
    protected ubyte getType()
    {
        cout << "getType ()" \n ;
        return cast(ubyte)type;
    }

}

void main ()
{
    cout << "main" \n ; 
    auto actor = new Actor ;
}
Apr 11 2007