iota result as member variable

[Alex via Digitalmars-d-learn]

Hi everybody,
doing some optimization on my code, I faced some strange question:
how to save a iota result in a class member?

Say I have
class A
{
     ??? member;

     auto testIter4()
     {
         return iota(0,5);
     }
}

void main()
{
     A a = new A();
     a.member = testIter4();
}

how would I declare the member?

What I found till now is this:
http://comments.gmane.org/gmane.comp.lang.d.learn/60129
where it is said, that I could use
inputRangeObject(testIter4)
and declare my member as InputRange!int

But then the random access is gone and, furthermore, looking into 
the source of std/range/interfaces.d found some lines (about line 
nr. 110) about performance and that the InputRangeObject has a 
performance penalty of about 3 times over using the iota struct 
directly. So, I could declare my member as typeof(iota(0))

Did I miss something?