Properties: a.b.c = 3

[Jarrett Billingsley]

On Wed, Jul 29, 2009 at 10:44 AM, Ary Borenszweig<ary at esperanto.org.ar> wrote:
> Andrei Alexandrescu wrote:
>>
>> Kagamin wrote:
>>>
>>> Andrei Alexandrescu Wrote:
>>>
>>>> Kagamin wrote:
>>>>>
>>>>> Andrei Alexandrescu Wrote:
>>>>>>
>>>>>> The question is very simple: given that we're used with a
>>>>>> specific semantics for a.b.c = 3, how can we address the fact
>>>>>> that the semantics of this familiar operation is so different
>>>>>> (and likely so useless) when properties replace fields?
>>>>>
>>>>> You're solving problems that never came to life. Well... only as
>>>>> syntetic examples.
>>>>
>>>> IMHO it's quite the contrary, a.b.c = 3 is a very simple and
>>>> concrete problem that emphatically shows we haven't gotten
>>>> properties up to snuff.
>>>
>>> Never saw this problem in C#.
>>
>> Of course you didn't. This is because C# doesn't have it - their structs
>> can't define properties.
>>
>> Andrei
>
> Yes they can. And also C# shows us the solution to the problem (similar to
> what Walter proposed).
>
> ---
> public class Bar
> {
>    public Foo Foo { get; set; }
> }
>
> public struct Foo
> {
>    public int Property { get; set; }
> }
>
> Bar bar = new Bar();
> Foo foo = new Foo();
> foo.Property = 10;
> bar.Foo = foo;
>
> bar.Foo.Property = 20; // line 16
> ---
>
> Error on line 16: Cannot modify the return value of 'Bar.Foo' because it is
> not a variable

Booom, exactly what I said about rvalues.