Getting the parameter index from all_tuples! | Bevy | Page 1

craggy hull Dec 9, 2023, 12:06 AM

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I want to collect all the members of the tuple like so:

Vec::from([self.0.into(), self.1.into(), self.2.into()])

However, I can't figure out how to do this with Bevy's all_tuples macro. Other tuple macro crates such as impl_trait_for_tuples and fortuples have this ability.

abstract forge Dec 9, 2023, 12:07 AM

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what have you tried?

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should be possible with a trait used to push tuple items to a vec

craggy hull Dec 9, 2023, 1:20 AM

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abstract forge should be possible with a trait used to push tuple items to a vec

I need to convert them before they are pushed, though.

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With the other crates, you can just get the tuple index.

abstract forge Dec 9, 2023, 1:21 AM

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yeah use your own trait, with your own impl being replicated by the macro

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that impl could well be vec.push(tup.$n.into())

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or something

craggy hull Dec 9, 2023, 1:23 AM

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Here's what I have - this doesn't work because $T is T0, not 0:

macro_rules! impl_class_names {
    ($($T:ident),*) => {
        impl<$($T: ConditionalClassName),*> ClassNamesTuple for ($($T,)*) {
            fn to_vec(self) -> Vec<Option<String>> {
                Vec::from([$(self.$T.to_class()),* ])
            }
        }
    };
}

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With impl_trait_for_tuples if you say self.T it knows you want an index, not a type name.

abstract forge Dec 9, 2023, 1:28 AM

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ah hmm

craggy hull Dec 9, 2023, 1:28 AM

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I'm using that package now, but I wanted to migrate to the bevy solution and reduce my dependencies.

abstract forge Dec 9, 2023, 1:28 AM

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yeah looking at how its used in bevy i think its meant as a type system only thing?

craggy hull Dec 9, 2023, 1:28 AM

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Hmmm, ok

abstract forge Dec 9, 2023, 1:28 AM

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mainly used to act on types, like in queries, bundles, etc

#Getting the parameter index from all_tuples!