Properties: a.b.c = 3

[Michel Fortin]

On 2009-07-28 22:33:53 -0400, Walter Bright <newshound1 at digitalmars.com> said:

> The issue is what if b is a property, returns a temporary object, and 
> that temp's .c field is uselessly set to 3?
> 
> It's a classic problem with properties that are implemented as functions.

With the local namespace approach I propsed a little while ago, you 
could allow "subproperties":

	namespace a {
		namespace b {
			namespace c {
				int opGet() {...}
				void opAssign(int) {...}
			}
		}
	}

or (alternate syntax for the above):

	int a.b.c.opGet() {...}
	void a.b.c.opAssign(int) {...}

Although it'd be somewhat clumbersome to redefine every member of a 
struct like this each time you make a property just so assigning to it 
works fine (I guess a mixin or some compiler magic could help).

> I don't see how C#'s special property syntax adds any value for dealing 
> with this.

Me neither.

> One thought I had was to simply disallow the '.' to appear after a 
> function style property.

I think that's a little harsh. If you return something by reference 
(like an object), the waterver you do to that object won't be lost. 
It's for value types (like structs) that this is a problem.


-- 
Michel Fortin
michel.fortin at michelf.com
http://michelf.com/