[Issue 5056] Warning against virtual method call from constructor

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=5056



--- Comment #5 from Steven Schveighoffer <schveiguy at yahoo.com> 2010-10-16 10:43:10 PDT ---
(In reply to comment #4)
> The really bad thing is that D doesn't allow you to set up a sub class before
> calling the super constructor. Consider this:
> 
> class Foo : Moo {
>   int stuff;
>   this(int stuff_) {
>     this.stuff = stuff_;
>     super();
>   }
>   override int get_stuff() {
>      return stuff;
>   }
> }
> 
> This won't compile, because the compiler forces you to do the super ctor call
> _before_ setting up any members. This was probably thought as a feature to
> ensure "correct" construction, but it just doesn't work because the super ctor
> could call virtual functions. And it's really hard to work this around.

Hm... I just tried it, it does work.  Were you thinking of something else?

example:

import std.stdio;

class A
{
    this()
    {
        foo(1);
    }

    void foo(int x)
    {
        writeln("A.foo");
    }
}

class B : A
{
    int x;
    this()
    {
        writeln("B.this");
        x = 5;
        super();
    }

    override void foo(int x)
    {
        writeln("B: ", this.x);
    }
}

void main()
{
    auto b = new B;
}

prints:

B.this
B: 5

-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------