Re: [Vala] How should I handle a constructor that fails?

[Jiří Zárevúcky <zarevucky jiri gmail com>]

You can't throw from the construct block, but you can throw from the
construction method. Thus, the correct way would be:

> class Foo : Object {
>        string filename { get; set; }
>
>        public Foo.with_file (string filename) throws IOError{
>                this.filename = filename;
>                if (!any_test_you_need)
>                      throw new IOError.FILE_NOT_FOUND("Requested file could not be found.");
>        }
>
> }

2009/6/16 Sam Danielson <samdanielson gmail com>:
> What should I do in a construct block when the normal thing would be
> to throw? Can object instantiation be stopped by an error like in C++
> or is the vala way to let construction continue and then set a zombie
> flag?
>
> Maybe a static method that creates an object, checks a zombie flag,
> and then throws if true could masquerade as the actual constructor.
> That's what I would do but it almost seems like a workaround.
>
> Forgive me for having very little experience with both C# and GObject
> and therefore lacking the ability to infer something so simple. Is
> there a preferred way to signal a failed constructor to the caller?
>
> Here is an example of what I'm talking about.
>
>
> errordomain IOError {
>    FILE_NOT_FOUND
> }
>
> class Foo : Object {
>        string filename { get; set; }
>        public bool failed;
>
>        private Foo.with_file_ (string filename) {
>                this.filename = filename;
>        }
>
>        public static Foo with_file (string filename) throws IOError {
>                var foo = new Foo.with_file_ (filename);
>                if (foo.failed) throw new IOError.FILE_NOT_FOUND("Requested file
> could not be found.");
>                return foo;
>        }
>
>        construct {
>                this.failed = true;
>        }
> }
>
> void main () {
>        try {
>                var foo = Foo.with_file ("test");
>                message ("ok");
>        }
>        catch {
>                message ("error");
>        }
> }
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