Derived properties #53
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ekr-cfa
requested changes
Sep 30, 2024
src/people.rs
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| @@ -60,6 +67,15 @@ macro_rules! define_person_property { | |||
| pub struct $person_property; | |||
| impl $crate::people::PersonProperty for $person_property { | |||
| type Value = $value; | |||
| fn is_derived() -> bool { | |||
| false | |||
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You could make this a default.
src/people.rs
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| } | ||
| fn dependencies() -> Vec<std::any::TypeId> { | ||
| panic!("Property not derived"); | ||
| } |
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These can also be defaults.
| impl $crate::people::PersonProperty for $derived_property { | ||
| type Value = $value; | ||
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| fn calculate(context: &$crate::context::Context, person_id: $crate::people::PersonId) -> Self::Value { |
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Given that initialize and calculate are the same, why not just have initialize?
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Overloading the meaning of a single function seems not ideal to me, this is more explicit
src/people.rs
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| let person = context.add_person(); | ||
| context.set_person_property(person, Age, 50); | ||
| context.set_person_property(person, IsRunner, false); |
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You need to stop people from externally calling set_person_property() on derived. I think I would do this by having a set_person_property_int() that is private but called by set_person_property()
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This PR adds derived properties, for example:
The macro takes a list of dependent properties and a closure which computes the property from those dependencies.
Derived properties can be used as other properties (with
get_person_property) etc.; they are recomputed whenever a dependency changes (and will also emit a change event).As a side effect of needing to do some lazy registration of dependencies if the property is derived, I needed to introduce a wrapper around subscribing to person property changes, which I think is not ideal:
In particular, I think it's probably pretty easy to mess up the order of current and previous.
Open to suggestions on how to handle this better