*final* class member (D2)

[Simen Kjaeraas]

On Wed, 13 Feb 2008 17:07:47 +0100, Denton Cockburn <diboss at hotmail.com>  
wrote:

> On Wed, 13 Feb 2008 10:59:26 -0500, Denton Cockburn wrote:
>
>> How do I do this?  I'm trying to create a class member here that needs  
>> to
>> be initialized in the constructor, but cannot be changed later.
>>
>> class A
>> {
>>    (const doesn't work) real delegate() dg; // this is that
>>    function;
>>
>>    this(real delegate() dg) { this.dg = dg; }
>> }
>>
>> class B
>> {
>>    real foo() { return 3.5; }
>> }
>>
>> class C
>> {
>>    real foo() { return 4.5; }
>> }
>>
>> void main()
>> {
>>    auto b = new B;
>>    auto a = new A(&b.foo);
>>    auto c = new C;
>>    a.fitness = &c.foo; // I want this to be an error
>> }
>
> formatting issues:
>
> (const doesn't work) real delegate() dg; // this is that
>    function;
>
> should be:
>
> (const doesn't work) real delegate() dg; // this is that function
>


You could make the delegate private, and use a function to call it.

class A
{
private:
	real delegate() m_dg;
public:
	real dg()
	{
		return m_dg();
	}
	this(real delegate() _dg)
	{
		m_dg = _dg;
	}
}

Of course, private in D only means module-private, so whoever makes  
changes to the module might still break things, but for anyone just  
importing it, the problem should be gone.