Generic producers about otto

[JakeWharton]

At runtime T is basically just Object which is why you won't see it producing events for whatever generic type you specify.

[romainpiel]

I see so there is no way to know what's returned by produceEvent(), fair enough. It was just an idea, no worries.

[edenman]

@JakeWharton could we do this when codegen is added, since it happens at compile time? I'm assuming the annotation processor gets generic type information...ignore me if it doesn't.

[pyricau]

The annotation processor gets generic type information. It get can as much information as you can get by reading the java code (except the code within methods of course).

When reading this:

public class MyClass<T> {

    T lastEvent;

    @Produce
    public T produceEvent() {
        return lastEvent;
    }
}

I don't see any information about the kind of object this might produce. Of course, if we now create a MySubclass extends MyClass<String>, that's another story..

[romainpiel]

Actually that's exactly my use case. I'd like to implement stuff in my generic class that will be inherited by subclasses with types.
Ideally it would be nice if I'd have to skip this workaround:

public class MySubclass extends MyClass<String> {

    String lastEvent;

    @Produce
    public String produceEvent() {
        return lastEvent;
    }
}

(ie instantiating my producer in each subclass)

[pyricau]

This won't be possible with the current Otto version because we do not walk the class hierarchy.

With 2.0 we will switch to code generation and take parent classes into account. I know this use case is technically feasible, I don't know yet how easy it's going to be.

[romainpiel]

Sweet! I'll keep watching then 👍

[swankjesse]

We have the type resolution technology, but I don't think it's worth supporting. To get this really right you'd need to make register() take a type argument, which I find rather ugly.

[pyricau]

I don't think so.

public class MyClass<T> {

    T lastEvent;

    @Produce
    public T produceEvent() {
        return lastEvent;
    }
}
public class MySubclass extends MyClass<String> {}

if I register an instance of MySubclass, I do not need any type argument, we can already determine (both at compile time and runtime) that it's going to produce a String.

I'm not sure there's enough value to implement this though.

[JakeWharton]

I vote for not supporting. This can come later if we determine it's really, really needed.

[fred8]

Hi all,
Just coming on this thread now. I think it would be interesting to add it. I have a bunch of events that are basically very close and I would like very much to be able to create a generic one.
Anyway to submit a pull request?

Thank you!