• Neil Vice (30/30) Mar 10 2008 Just thought I'd post regarding a curiosity with constructors and const

"Neil Vice" <psgdg swiftdsl.com.au> writes:

Just thought I'd post regarding a curiosity with constructors and const 
members (2.012).

Const members can only be initialised from within constructors, not by 
methods called by constructors. Passing const members into methods as out 
parameters causes them to be typed 'const' and as such not assignable. All 
this makes it rather difficult to factor out common constructor code in the 
case where one constructor cannot simply call the other.

What apprently does work is passing inline delegates to a method that assign 
to the members e.g.

class Test : Parent
{
    const int member;

    public this(string path)
    {
        super(path);
        init(delegate(in int value) { member = value; } );
    }

    public this(Parent copy)
    {
        super(copy);
        init(delegate(in int value) { member = value; } );
    }

    protected void init(void delegate(in int) assign)
    {
        // Realistically something based on a member of Parent
        // and much longer, otherwise what's the point? =)
        assign(0);
    }
}

Ugly? Yes; and yet...