Re: [Vala] Cannot have field and method with the same name

[Anatol Pomozov <anatol pomozov gmail com>]

On Fri, Dec 3, 2010 at 5:08 PM, Evan Nemerson <evan coeus-group com> wrote:
> On Fri, 2010-12-03 at 15:38 -0800, Anatol Pomozov wrote:
> > Hi,
> >
> > I have a class that contains a field and method with the same name,
> > and Valac does not like it. What is the reason? Other languages
> > (C#/Java) allow it. You have to use () for method so you know whether
> > you access method or field.
>
> I'm not a C# or Java programmer, so feel free to correct me if I'm wrong
> but...
>
> Java doesn't have delegates. In this example, what is X?

Ah, delegates, functions that act as variables. Now it a little bit clearer.

> public class Foo {
>  public boolean stop = true;
>
>  public boolean stop () {
>    return true;
>  }
>
>  public Foo () {
>    var X = this.stop;
>  }
> }
This example does not work. valac 0.11 complains with quite weird message

a.vala:11.7-11.18: error: Assignment: Cannot convert from `Foo.stop'
to `Foo.stop'
                var x = this.stop;

We cannot use var - we need to declare Delegate type here. Something like

MyDelegateType x = this.stop;

But in this case it is clear that we want function. We cannot assign
field/property to a delegate, isn't it?

Sorry for stubbornness - I learn Vala and trying to illuminate all
dark corners. I am looking for an example that clearly shows why we
cannot have field/method with the same name.

> Actually, now that I think about it, I don't think Java does type
> inferencing either.
It is planned for Java7.
> In addition to type inferencing issues, this could cause problems with
> generics, and would generally be a pain to read.
Not sure what do you mean here.

> C# doesn't allow this either. AFAIK, in C# you can overload methods so
> that the most appropriate method is called, but you can't have a method
> and a property with the same name. Example:
>
> class Foo {
>  bool stop () {
>    return true;
>  }
>
>  // No problem
>  bool stop (bool a) {
>    return false;
>  }
>
>  // Problem
>  bool stop = false;
>
>  public static void Main () {
>    var foo = new Foo ();
>  }
> }
>
> Overloading methods is a separate issue, which Aleksander Wabik already
> explained.
>
> > anatol:vala $ valac a.vala
> > a.vala:4.3-4.21: error: `Foo' already contains a definition for `stop'
> >   public boolean stop() {
> >   ^^^^^^^^^^^^^^^^^^^
> > a.vala:2.3-2.21: note: previous definition of `stop' was here
> >   public boolean stop = true;
> >   ^^^^^^^^^^^^^^^^^^^
> > Compilation failed: 1 error(s), 0 warning(s)
>
> Amusingly, this is basically the same error message as you get in C# (at
> least from mcs):
>
> test.cs(12,8): error CS0102: The type `Foo' already contains a
> definition for `stop'
> test.cs(2,8): (Location of the symbol related to previous error)
> Compilation failed: 1 error(s), 0 warnings

Oops, my statement that it works in C# is wrong. I was looking at
incorrect C# example.