How can I construct a Query value? (not a QueryState value)

[bbarker]

QueryState values appear to be stateful, so I don't really want to pass those around, especially when the intention is to re-use them. But I'm working in a context (serialization macros) where I need to construct Queries. world.query returns a QueryState. Is there a way to construct a Query instead?

[tim-blackbird]

I'm not sure why QueryState being 'stateful' matters here.
Keep in mind that Query is just a wrapper around QueryState.
You can construct a Query via SystemState.

[bbarker]

Thanks, I'll take a look at SystemState. To clarify a bit about my apprehension, I had a code snippet that looks like this, where self is &QueryState:

        let count = self.iter().count();
        match serializer.serialize_seq(Some(count)) {
            Ok(mut serseq) => {
                self.iter().for_each(|ent_comp| {
                    serseq.serialize_element(&ent_comp).unwrap();
                });
                serseq.end()
            }
            Err(er) => Err(er),
        }
    }

Since QueryState needs to be mutable to iterate over it, it just seemed like the interface might be hiding some mutation that occurred and I might not be able to reuse it.

[bbarker]

Well, I see that iter() is the same for Query in regard to needing mutable access. So maybe I should just stick with QueryState and explore along those lines.