D rawkz! -- custom writefln formats

[H. S. Teoh]

On Thu, Jan 17, 2013 at 08:20:49PM +0100, Andrej Mitrovic wrote:
> On 1/16/13, H. S. Teoh <hsteoh at quickfur.ath.cx> wrote:
> > I'm guessing that most D users don't realize extent of the flexibility
> > of std.format
> 
> There's a problem:
> 
> module test;
> import std.stdio;
> 
> class C1 { }
> class C2 : C1
> {
>     void toString(scope void delegate(const(char)[]) put)
>     {
>         put("Subclass");
>     }
[...]

Hmm. The fact that this method didn't give a compiler warning/error
about missing an "override" keyword indicates the root of the problem:
you need to define toString in C1 and override it in C2, otherwise the
toString method will not be visible via a C1 reference. (I've run into
this before.)

Ideally the toString variants should be put in Object, but I'm not sure
if it will work well (in particular, if you overload toString with
template arguments on character type, it will not be virtual so there
may be some use cases that won't work).


T

-- 
"Computer Science is no more about computers than astronomy is about telescopes." -- E.W. Dijkstra